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The mm Universe 2025 conference will be hosted at the Kavli Institute for Cosmological Physics (KICP) at the University of Chicago from June 23-27, 2025.
This conference will bring together the international scientific community to discuss the latest progress in both theoretical and observational topics related to the mm Universe, from stellar
to cosmological scales. The broad range of topics to be discussed include:
While it is devoted to observations of the Universe at mm-wavelengths, as multi-wavelength
analyses are critical to understanding astrophysical processes and testing cosmological models,
the conference series is also opened to results and observations at other wavelengths. Registration and abstract submission will open November 13, 2024. Abstract submission closed February 14,2025. Registration closed in March 2025.
With the 3rd generation camera on the South Pole Telescope, SPT-3G, over 10K square degrees of the southern sky has been surveyed in Stokes I/Q/U at frequencies of 90,150, and 220 GHz with noise levels in coadded intensity ranging from 2 to 9 $\mu$K-arcmin at roughly arcminute resolution. This provides insights over the full range in cosmic time, from the early universe to nearby objects. Measurements of the lensed primary CMB provide precise probes of cosmology, Sunyaev-Zeldovich effects probe reionization and galaxy clusters, dust emission marks locations of high-z galaxy candidates, variable active galactic nuclei are detected and monitored, and Galactic transients are discovered. I will discuss recent results from SPT-3G on these fronts and more.
The sixth public data release (DR6) of the Atacama Cosmology Telescope includes observations in total intensity and linear polarization taken between 2017 and 2022 in three frequency bands—98, 150 and 220 GHz—covering 19,000 square degrees. With white noise levels three times lower than those of Planck, the arcminute-resolution observations provide strong constraints on the physics governing the polarization and damping tail of the CMB. We find that the DR6 CMB power spectra are well fit by the ΛCDM cosmological model. By combining DR6 data with external datasets, including Planck primary CMB measurements, CMB lensing and DESI Year-1 baryon acoustic oscillation data, we test a wide range of assumptions underlying the ΛCDM model and constrain a large number of proposed extensions. These include modifications to the initial conditions, (pre-)recombination physics, particle phenomenology and gravity. We find no statistical evidence for deviations from ΛCDM, which, for example, significantly reduces the allowed parameter space for models introduced to increase the Hubble constant. In this talk, I will provide a brief overview of the dataset and analysis pipeline, highlight the key cosmological results, and discuss their implications.
Cosmic Microwave Background (CMB) measurements and other observations, combined with relatively basic theory, allow us to extrapolate back to when our Universe had a temperature $>10^{12}$ Kelvin, and to infer the very particular set of conditions which pertained at that time - almost uniform plasma with adiabatic, Gaussian, scale-free perturbations. The leading hypothesis for how those conditions were set up posits a brief burst of exponential hyper-expansion---the so-called Inflation theory. If inflation did occur it will have injected into the fabric of spacetime a background of gravitational waves, which may be detectable through their imprint in the CMB polarization pattern.
The current world leaders in the quest to detect this signal are the BICEP/Keck experiments which are located at the South Pole in Antarctica. I will describe the existing BK18 results as well as the experimental progress since then, and the prospect for a next generation "de-lensed" result in conjunction with the South Pole Telescope (SPT).
We present measurements of large-scale cosmic microwave background (CMB) E-mode polarization from the Cosmology Large Angular Scale Surveyor (CLASS) 90 GHz data. Using 115 det-yr of observations collected through 2024 with a variable-delay polarization modulator, we achieved a polarization sensitivity of $78\,\mathrm{\mu K\,arcmin}$, comparable to Planck at similar frequencies. We demonstrate effective mitigation of systematic errors and address challenges to large-angular-scale power recovery posed by time-domain filtering in maximum-likelihood map-making. A novel implementation of the pixel-space transfer matrix is presented, which enables efficient filtering simulations and bias correction in the power spectrum using the quadratic cross-spectrum estimator. Overall, we achieved an unbiased time-domain filtering correction to recover the largest angular scale polarization, with the only power deficit, arising from map-making non-linearity, characterized to be less than 3%. Through cross-correlation with Planck, we detected the cosmic reionization at $99.4\%$ significance and measured the reionization optical depth $\tau=0.053 ^{+0.018}_{-0.019}$, marking the first ground-based attempt at such a measurement. At intermediate angular scales ($\ell > 30$), our results, both independently and in cross-correlation with Planck, remain fully consistent with Planck’s measurements.
The Simons Observatory (SO) is a cosmic microwave background (CMB) experiment situated on the Chajnantor Plateau in Chile's Atacama Desert. The observatory comprises seven mm-wave telescopes operating across six frequency bands (30-280 GHz). Six 60cm Small Aperture Telescopes (SATs) focus on detecting primordial B-mode polarization signatures of cosmic inflation in two deep, low-galactic-foreground sky patches. Complementing these, a 6m Large Aperture Telescope (LAT) targets precision measurements of neutrino properties, galaxy cluster physics via the Sunyaev-Zeldovich effect, dark matter distribution through gravitational lensing, and transient mm-wave phenomena. This presentation will provide an overview of the observatory and its science goals, updates on construction progress, commissioning activities, and preliminary data analysis and a look forward to SO's planned expansions and scientific synergies with other next-generation optical and infrared survey instruments.
SPIDER is a powerful balloon-borne instrument designed to map the polarization of the millimeter-wave sky from above the bulk of the Earth’s obscuring atmosphere. SPIDER leverages the pristine observing conditions and long flight time provided by the NASA Long-Duration Balloon (LDB) platform to produce deep maps over a large area (~10% of the sky) and broad frequency range (95, 150, 280 GHz). SPIDER also serves as an important technological proving ground and training program toward future space missions. SPIDER’s 2015 flight yielded published constraints on the circular polarization and B-mode polarization of the cosmic microwave background (CMB), as well as intriguing hints of complex behavior in the polarized emission of Galactic dust. The 280 GHz data from SPIDER’s 2022-23 flight promise further insight into Galactic dust, with relevance to foreground studies for future studies of the CMB.
The accuracy of the interpretation of the current generation of late-time cosmology probes is greatly limited by the theorists' ability to predict the response of baryons. This will only get more difficult in the coming years with the upcoming surveys (DESI-BGS, Euclid, LSST, 4-most, Simons) mapping our sky with unprecedented precision.
In this talk, I will discuss some of the efforts towards this challenge on the simulation side. I will, in particular, focus on the new generation of simulations, the FLAMINGO suite, designed to be virtual twins of the Stage IV cosmology surveys. This suite includes the largest simulation ever run to z=0 and exploits a state-of-the-art baryon physics model calibrated to the relevant data. Variations in the physics, trained via machine learning techniques, allow us to encompass the uncertainty in the modeling. Outputs in observer space, such as X-ray, stellar light and SZ lightcones are produced and are used to validate the simulations. This talk will have a special focus on SZ-probes and data producs extracted from the simulations. This talk is also a invitation to collaborate and make use of this data for your research.
Exascale computing is driving a new era of cosmological simulations, enabling unprecedented precision in modeling large-scale structure formation and its interplay with the CMB. One example is the Frontier Exascale Simulation, which evolves 4 trillion particles within a 4.6 Gpc box, capturing the detailed growth of structure across cosmic time. These simulations provide high-fidelity predictions for CMB measurements, including full sky kinematic and thermal SZ maps, as well as extremely high statistics of rare objects, ideal for cluster studies. The vast datasets generated also offer new opportunities for machine learning applications, improving model emulation and parameter inference for upcoming surveys. This talk will explore the details of the Frontier Exascale Simulation and highlight its implications for CMB science, particularly in the context of next-generation experiments.
In Λ Cold Dark Matter (ΛCDM) cosmology, galaxy clusters form via the hierarchical merging/accretion of formerly separate Dark Matter halo systems containing cold and collisionless DM. Due to the non-turbulent nature of CDM, we would expect the most massive and brightest cluster galaxy (BCG) to come to rest at the gravitational center of the cluster’s DM halo. To test this prediction, we looked at the spectroscopic and photometric properties of clusters selected from the 2500-Square-Degree South Pole Telescope (SPT)-Sunyaev–Zel’dovich (SZ) Survey. We constructed a sample of 81 clusters with over 15 spectroscopically confirmed cluster members including the BCG (Nmem > 15) such that we were able to reliably measure the median cluster redshift (z), cluster velocity dispersion (σ), and BCG peculiar velocity (vp). From these, we measure the normalized peculiar velocity (vp/σ) which tells us the relative motion of the BCG with respect to the cosmic recession of the cluster normalized by the spread of motion of cluster members. We compare the observed distribution of vp/σ to a normal distribution (NDvp=0). The offset values in NDvp=0 arise solely from measurement uncertainty and, therefore, NDvp=0 characterize the situation where the BCG is at rest with respect to the cluster. We find that the observed offsets are beyond what is expected due to measurement error alone, suggesting that BCGs exhibit peculiar motion with respect to their host halo.
Galaxy clusters are powerful probes used to constrain the cosmology of our universe. However, they are peppered with several systematic biases such as projection effects. Of them, the orientation of triaxial clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (i.e., richness and weak-lensing signal) of galaxy clusters. We used the observed shape of the central, Brightest Cluster Galaxy (BCG) as a proxy for the orientation along the line-of-sight for clusters selected via the Sunyaev-Zel’dovich (SZ) effect from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) surveys, matched to optically selected clusters from the Dark Energy Survey Year 3 (DES). In this talk, I will show that there is not only a significant correlation between the BCG shape and the observed weak lensing signal but also a non-trivial difference from the expected effect of triaxiality from simulations. We speculate that the intrinsic shape of the BCG reflects not just the orientation angle, but also the assembly history of the cluster. I will discuss the implications and results of testing this hypothesis.
Galaxy cluster formation is driven by a variety of complicated physical processes that affect their growth and evolution through cosmic time. As a result, the matter distribution within the cluster, and therefore, its shape, can be a probe of these astrophysical processes and cosmology. Clusters grow through the accretion of new material, typically along two or three main filaments, giving them an elongated, triaxial morphology. In-falling material is thermalized primarily through a series of shocks, however, the underlying physical processes governing these shocks are not well understood. To better understand the growth and evolution of clusters, we have developed a pipeline for modeling their three-dimensional triaxial morphology from which we can infer their masses and the thermalization efficiency in the cluster outskirts within a triaxial basis. This analysis will be performed on the Cluster HEritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE) sample of galaxy clusters. Utilizing X-ray data from XMM-Newton and Sunyaev-Zeldovich effect (SZE) maps from Planck and the Atacama Cosmology Telescope, a three-dimensional triaxial description of the cluster geometry is obtained. The addition of a weak lensing (WL) analysis using shear maps constructed from Subaru Suprime-Cam observations enables a measurement of total halo mass. Additionally, the thermalization efficiency in the cluster outskirts can be measured as the level of pressure support due to non-thermal motions in the region. We obtain radial profiles of the thermal pressure ($P_{th}$) from the direct X-ray and SZE measurements and the total pressure needed to offset gravity ($P_{tot}$) from the gravitational potential corresponding to the WL derived triaxial mass. The non-thermal pressure ($P_{nt}$) is then taken to be the difference between $P_{tot}$ and $P_{th}$. In this talk, I will present the results from this pipeline on two CHEX-MATE clusters, one elongated in the line of sight (Abell 1689) and another that is elongated in the plane of sky (Abell 2390). I will also include projections for the final results that can be obtained from the full CHEX-MATE sample based on these initial demonstrations.
We present a joint approach to studying galaxy clusters that combines X-ray data from the Chandra X-ray Observatory with millimeter data from both the South Pole Telescope (SPT) and the Planck satellite, leveraging the complementary capabilities of these three instruments. In particular, we exploited the high angular resolution of Chandra and SPT to map the innermost region of the cluster and the high sensitivity to the larger angular scales of Planck to constrain the outskirts and improve the estimation of the cosmic microwave background and the galactic thermal dust emissions. This joint analysis allows us to recover detailed thermodynamic profiles, such as density, pressure, temperature, and hydrostatic mass, over a wider radial range than would be possible with X-ray or SZ data alone. In addition to maximizing the accuracy of radial temperature measurements, our joint analysis allows us to test the consistency between X-ray and millimeter derivations of thermodynamic quantities via the introduction of a normalization parameter ($\eta_T$) between X-ray and millimeter temperature profiles. This parameter enables the extraction of other thermodynamic profiles without relying on spectroscopic temperature measurements at large radii, where such data are often sparse or unreliable, particularly for high-redshift or faint clusters. We apply our method to a sample of 10 clusters covering a wide range of masses, deriving hydrostatic mass and gas fraction profiles. As a byproduct, comparing our results with existing observations and simulations allows us to assess the systematics affecting these measurements, including cross-calibration issues between X-ray instruments.
Galaxy cluster mergers are rich sources of information to test both cluster astrophysics and cosmology. However, cluster mergers produce complex projected signals that are difficult to interpret from individual observational probes. Multi-probe constraints on both the gas and dark matter cluster components are necessary to infer merger parameters that are otherwise degenerate. We have developed ICM-SHOX (Improved Constraints on Mergers with SZ, Hydrodynamical simulations, Optical, and X-ray), a systematic framework to jointly infer cluster merger parameters quantitatively via a pipeline that directly compares a novel combination of multi-probe observables to mock observables derived from hydrodynamical simulations. In our first application of the ICM-SHOX pipeline to the MACS J0018.5+1626 system, we discovered a velocity-space decoupling of the gas and dark matter distributions, which we attribute to the different collisional properties of the two components. We are now obtaining new and deeper observations of MACS J0018.5+1626 to confirm the possible detection of a rare equatorial shock as a result of the merger. In another system, MACS J2129.4-0741, we find hints of a Bullet Cluster-like morphology in the X-ray data, which strongly suggests a plane-of-sky merger, along with high line of sight velocities in both the gas and dark matter, which strongly suggests a merger in that direction. We do not yet have a complete understanding of how to reconcile these observables. In this talk, I will provide an overview of these exciting cluster mergers and the status of our updated ICM-SHOX pipeline.
We will present measured noise spectra of horn-coupled microwave kinetic inductance detector (MKID) arrays. These detectors are tailored for next generation multi-kilo-pixel experiments that are designed to simultaneously characterize the polarization properties of both the cosmic microwave background (CMB) and Galactic dust emission. Each array element is sensitive to two polarizations and two spectral bands. A horn antenna is used to feed a planar orthomode transducer, which separates the two incoming polarizations. Microstrip diplexers composed of resonant-stub band-pass filters separate the radiation into 125 to 170 GHz and 190 to 280 GHz pass bands. The millimeter-wave power is ultimately coupled to a hybrid coplanar waveguide microwave kinetic inductance detector using a novel, broadband circuit developed by our collaboration. Our laboratory measurements focus on sensitivity (NET) and low-frequency noise.
One of the biggest challenges for Cosmic Microwave Background (CMB) experiments comes from our detector bandpass calibration. Uncertainties in bandpass can severely limit our measurements by limiting foreground removal and spectral fitting, which is particularly important for high-$\ell$ observations like cluster science using the Sunyaev-Zeldovich (SZ) effect. Currently, CMB experiments typically use a Fourier Transform Spectrometer (FTS) to measure the detector bandpasses. However, the resolution of the FTS is dependent on the length of the interferometer arms, leading to a need for increasingly large FTS instruments as CMB experiments require tighter constraints on detector bandpasses. Additionally, systematic effects like shifts in bandpass shape from uneven illumination from the FTS further limit the calibration uncertainties. As a complement to the FTS, we have developed a Frequency-selectable Laser Source (FLS) calibrator, which uses a laser with adjustable frequency housed in a calibrator that allows for varying degrees of laser power attenuation. We present several tests used to characterize the first prototype design of the FLS calibrator, as well as the improvements to the calibrator design currently underway.
Ground-based measurements of the cosmic microwave background are subjected to short-term sky noise primarily driven by poorly-mixed atmospheric water vapor. This noise causes brightness fluctuations in telescopes and limits accessible spatial scales on the sky in the absence of appropriate modulation. To better understand the observing environment and predict performance of future telescopes, we have deployed a 183 GHz water vapor radiometer (WVR) to Cerro Toco in the Chilean Andes, home to CLASS, Simons Observatory, and a proposed site for the future CMB-S4. Unique to this WVR is a custom two-stage optical design which allows it to scan 360 degrees in azimuth and do elevation sky-dips in an observing strategy similar to a typical CMB telescope. It is a copy of a unit already deployed to the South Pole, so data from these two instruments will further enable valuable comparisons of the observing conditions at the two sites.
Taurus is a mid-latitude super-pressure balloon mission to map the polarization of the cosmic microwave background (CMB) over about 70% of the sky, in four bands from 150 - 350 GHz, and with high fidelity on very large angular scales. The signal on these scales is sensitive to the timing and details of cosmic reionization by the first stars. Knowing the total optical depth of the reionized universe (τ) is also crucial to break degeneracies with other cosmological parameters, most notably the amplitude of scalar fluctuations and the sum of neutrino masses.
From its stratospheric balloon platform, Taurus will escape most of Earth's atmosphere and observe with a strategy designed to mitigate instrumental systematic errors on large scales. Balloon missions enable extremely sensitive detectors, minimal systematic contamination from the atmosphere, and access to high frequency bands critical to disentangling CMB signal from Galactic dust emission. Newer super-pressure balloons provide long-duration flights with access to the entire night sky from middle latitudes. With a month-long flight, Taurus can measure the optical depth τ with sensitivity approaching the sample variance limit. This measurement, and Taurus's high frequency maps, will serve as a force multiplier for other upcoming CMB experiments, greatly expanding what we can achieve as a community.
Over the past year, the proposal to build a high-frequency Small Aperture Telescope (SAT) to add to the Simons observatory has gradually become more and more consolidated. This project named Kairos is currently submitted for funding to the RI2 CNRS program (Recherche à risque et à impact) and has obtained the support of three institutes (IN2P3, INSU and INP). We propose to deploy a focal plane of about 30k LEKID detectors to observe the sky in two bands centered at 280 GHz and 340 GHz taking care of all the different sub-systems within the french collaboration. Adding a high frequency SAT to the pre-existing SATs will allow us to answer the outstanding question of mapping the polarized emission of interstellar dust with great sensitivity giving to the whole project a more precise measurement of the contamination of galactic dust emissions which currently constitutes one of the most limiting factors for CMB B-mode observations. We will present from a general point of view the instrumental configuration we propose to implement.
I will present high-resolution millimeter images of dust and gas in high-redshift dusty star-forming galaxies (DSFGs). SPT0418-47 ($z \approx$ 4.22) and SPT2147-50 ($z \approx 3.76$) are two of the most well-studied gravitationally lensed, high-redshift DSFGs selected by the South Pole Telescope. Using Atacama Large Millimeter/submillimeter Array (ALMA) observations of these galaxies, I create maps of dust continuum (160 and 380 $\mu$m), [CII], CO(7-6), [CI] (2-1), and, in SPT0418-47, water emission. Taking advantage of the galaxies' lensed nature, via state-of-the-art lens modeling tools, I am able to spatially resolve the extent of both dust and gas emission on sub-kiloparsec physical scales, revealing extended [CII] halos in both sources. In the image plane, I apply a wide range of prescribed conversion factors and log-linear relations to the measured line luminosities in both sources, deriving and comparing estimates of star-formation rates (SFR) from [CII], water, and CO emission, and of molecular gas masses from [CII], [CI], and CO emission; I use these estimates to study the Kennicutt-Schmidt relation and gas depletion times in both sources. My work reveals the power of multi-band observations in the millimeter window to deeply probe the ISM properties of gravitationally lensed, high-redshift galaxies, and will be expanded to a wider range of DSFGs in the coming years.
The BICEP3 telescope is a 95GHz CMB polarimeter located at the South Pole searching for inflationary gravitational waves. Directly measuring non-idealities in polarization between detector pairs and across the focal plane is useful for understanding how our constraints on r are impacted by E-to-B leakage. Further, measuring polarization angles in an absolute reference frame makes telescopes sensitive to potential signatures from EM parity violation such as cosmic birefringence. We calibrate our detectors on BICEP3 by observing a rotating polarized source (RPS) whose polarization is carefully referenced to gravity. Current birefringence constraints are limited to ~0.1° by calibration precision and statistical uncertainty, but as more CMB data are gathered, calibration uncertainty becomes dominant. This talk will discuss the challenges in building a highly precise (~0.03°) polarization calibrator and ensuring true absolute calibration.
The kinetic Sunyaev-Zel'dovich effect (kSZ) and patchy screening effect are two complementary cosmic microwave background (CMB) probes of the reionization era. The kSZ effect is a relatively strong signal, but is difficult to disentangle from other sources of temperature anisotropy, whereas patchy screening is weaker but can be reconstructed using the cleaner polarization channel. Here, we explore the potential of using upcoming CMB surveys to correlate a reconstructed map of patchy screening with (the square of) the kSZ map, and what a detection of this cross-correlation would mean for reionization science. To do this, we use simulations and theory to quantify the contributions to this signal from different redshifts. We then use the expected survey properties for CMB-S4 and CMB-HD to make detection forecasts. We find that, for or our fiducial reionization scenario, CMB-S4 will obtain a hint of this signal at up to 1.8σ, and CMB-HD will detect it at up to 14σ. We explore the physical interpretation of the signal and find that it is uniquely sensitive to the first half of reionization and to the bispectrum of the ionized gas distribution.
As they travel through the Universe, a small fraction of cosmic microwave background (CMB) photons scatter off free electrons from the gaseous halos of moving galaxies leaving a temperature signal: the kinematic Sunyaev-Zel'dovich effect (kSZ). In this work, we precisely measure this effect with velocity stacking to infer gas profiles around galaxies and their dependence on galaxy properties, an important input for galaxy formation models. We use spectroscopically confirmed luminous red galaxies from the Dark Energy Spectroscopic Instrument (DESI) Y1, which overlap with the Atacama Cosmology Telescope (ACT) Data Release 6 temperature maps over more than 4,000 square degrees. The kSZ effect is measured with high significance (SNR~10), allowing us to explore its evolution with various parameters. We find no trend with redshift, but clear trends with stellar mass and absolute magnitude in g, r, and z bands. Our results suggest that the gas is much more extended than the dark matter and that there is a significant amount of additional energy injection compared to cosmological hydrodynamical simulations. Additionally, we present the first estimate of the kSZ signal from the DESI Y1 bright galaxy sample and emission-line galaxies, whose features match qualitative expectations. We also confirm the consistency of a previous photometric kSZ measurement using DESI luminous red galaxies, which, while offering comparable statistical power, may be subject to more complex systematic effects, thereby increasing confidence in those results. Finally, we provide an SNR forecast for stacking kSZ measurements in future experiments with the latest ACT maps, such as DESI Y3 and the Rubin Observatory Legacy Survey of Space and Time, with the latter reaching an SNR of ~50. We expect our results will substantially reduce baryonic uncertainties in cosmological lensing analyses and hydrodynamical simulations.
For years, pairs of clusters have been studied in a wide range of frequencies to try to detect filaments of matter between them using. X-ray emission, the Sunyaev-Zel'dovich (SZ) effect and radio emission have all been used. Such studies are closely connected to the ‘missing baryon’ problem, an open issue in modern cosmology: the quantity of baryonic matter observed in the local Universe is much smaller than that of the LCDM model. Hydrodynamical simulations of large scale structure show that at low redshifts, these missing baryons should be in the warm-hot intergalactic medium (WHIM), arranged in filaments connecting galaxy clusters, that all together form the cosmic web. The first significant detection of an individual filamentary structure between galaxy clusters with the SZ effect was in the Abell 399 and Abell 401 cluster pair. This triggered a search for filaments in other pairs of galaxy clusters, with a few candidates discovered in SZ maps from the Atacama Cosmology Telescope (ACT). X-ray and SZ observations have always been interlaced for discovering and characterizing galaxy clusters and filaments. We are obtaining XMM-Newton X-ray data and high resolution MUSTANG-2 SZ data for two galaxy cluster pairs in which ACT data show the possible presence of a bridge. We are analyzing these systems by jointly modelling the ACT and MUSTANG-2 SZ measurements together with the XMM-Newton X-ray maps in the energy band between 0.4 and 7.2 keV. This study will help us to better constrain the physical properties of these filaments and to deepen our understanding of the cosmic web.
The Cluster HEritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE) provides a comprehensive dataset of 118 galaxy clusters, offering insights into their morphology within a volume-limited and mass-limited sample of the universe. In this work, we introduce a three-dimensional modeling framework CLUMP-3D that integrates multiwavelength observations to analyze the matter distribution in CHEX-MATE clusters. We focus on a triaxial analysis of the intracluster medium by combining X-ray observations, Planck-derived Sunyaev–Zel’dovich effect data, and complementary ground-based measurements. We apply our method to the CHEX-MATE DR1 sample as an initial step toward a full survey analysis, examining the distribution of geometric parameters such as gas axial ratios and elongation. A companion study that incorporates lensing data to characterize the dark matter distribution will be presented by Gavidia at this conference.
Cold fronts in galaxy clusters, seen as sharp discontinuities in X-ray surface brightness and temperature, offer crucial insights into the physical processes shaping the intracluster medium (ICM). These structures not only trace a cluster’s dynamical history but also serve as natural laboratories for studying transport processes such as thermal conduction. In this talk, we investigate the formation and evolution of cold fronts in two distinct systems: the Perseus Cluster, where large-scale sloshing cold fronts extend to remarkable radii, and Abell 2319, a massive and hot merging cluster that provides an ideal setting to test the effects of thermal conduction.
Using high-resolution magnetohydrodynamic (MHD) simulations with the AREPO code, we explore how merger-driven gas motions shape cold fronts and identify the conditions that allow features like the long-lived cold fronts in Perseus to persist. We use Abell 2319 as a case study to examine how different levels of thermal conduction influence cold front morphology and the overall thermal structure of the cluster. By comparing simulations with varying initial conditions to observations, we provide new constraints on the microphysics of the ICM. Our results establish a theoretical framework for interpreting current and future X-ray observations, refining our understanding of gas dynamics and transport processes in galaxy clusters.
Filaments connecting galaxy clusters appear to contain the vast majority of the ‘missing baryons’ in the form of a warm-hot intergalactic medium (WHIM) gas and are expected to emit a diffuse soft X-ray signal. Utilizing eROSITA’s sensitivity in the soft X-ray band, down to 0.2 keV, along with its wide field of view, raster scanning, and stable background, we are able to characterize this diffuse signal. Data from the eROSITA performance verification observations of the Abell 3391/3395 field have previously been analyzed to constrain the properties of three separate filamentary connections between clusters. However, extracting filamentary gas temperatures and densities from spectral fits to the eROSITA data is challenging, and has limited these analyses. We thus aim to combine the eROSITA data with thermal Sunyaev-Zeldovich (SZ) measurements from Planck and SPT to better probe the density and temperature distributions of the filamentary gas in this system. I will present an update on this analysis, including initial estimates on parameter constraints and remaining tasks.
As CMB telescopes—such as the current and upcoming BICEP/Keck instruments and the future CMB‐S4 experiment—strive to measure primordial B-modes via precise polarimetry, rigorous characterization of optical materials under cryogenic conditions is increasingly critical. For instance, losses in transmissive optics elevate photon noise, degrading mapping speed and overall sensitivity. Meeting the stringent demands of these high-contrast, high-throughput imaging systems requires a precise understanding of the complex permittivity of laminates and bulk materials, which in turn guides the design of optical components such as anti‐reflection coatings and refractive elements.
To address these challenges, we have commissioned a series of high-quality factor quasioptical Fabry–Pérot resonant cavities that span 75 GHz - 330 GHz and that are compatible with a quick-turnaround 4 K cryostat. These hemispherical resonators enable precise metrology of low-loss bulk and thin dielectrics used as lenses, filters, and laminates throughout the optical chain. These developments not only refine our understanding of photon loading in current instruments, such as BICEP3 and BICEP Array, but also inform the selection of materials in the design of upcoming CMB telescopes. Ultimately, our results also broadly contribute to wide-ranging mm-wave instrumentation efforts. We discuss the development, design, and characterization of these cavities, as well as measurements of the index and loss of various materials commonly employed in millimeter-wave instruments.
In this talk I will discuss the planned daily public release of monitored source light curves and transient alerts from the (Advanced) Simons Observatory provided by daily survey-scale observations in the millimeter. The scan strategy for the Large Aperture Telescope (LAT) is designed to cover a high fraction of the survey volume once every few days, providing excellent coverage of (time-varying) sources alongside the CMB study. In addition to long-term results from (e.g.) k- and t-SZ views on clusters, the LAT’s high sensitivity and large survey area mean it is primed to provide daily updates on the fluxes of both known and unknown sources. In this talk, I will describe both our survey estimates (O~10’000 objects visible daily, with O~100’000 available with weekly and monthly co-adds of data) and the open-source technical infrastructure (databases, APIs, and our overarching pipeline) that we are building to provide target photon-to-public catalog times of 30 hours. I will discuss our open data policies, strategy, and formats, including lightcurves for AGN, flaring stars, and asteroids, which will be made available immediately after data processing. I will provide a (rough) timeline for data availability, with our expectation that daily light-curves should be available in open beta by early 2027.
Component separation is critical in CMB data analysis to clean foregrounds from CMB. The deep convolutional neural networks (CNN) have been increasingly useful in image segmentation problems of various fields to reconstruct the signal. I have built a hybrid CNN architecture in wavelet space (specifically in Needlet space ) to separate foregrounds from CMB that works in multi-resolution spherical data. This hybrid method introduces fewer residuals in recovered CMB than the conventional component separation techniques. I applied the trained network to Planck data. In this talk, I will discuss the robustness of the method in the recovery of CMB map irrespective of foreground complexity. The results suggest that this hybrid architecture can provide a promising alternative approach to the component separation of CMB observations.
Most of the instruments currently observing at mm wavelenghts are located in the Southern Hemisphere. Those few in the Northern Hemisphere are mostly focused on observations of large scale CMB anisotropies with small aperture telescopes (e.g. AliCMB, GroundBIRD). Therefore, there is a gap for an instrument with a large mirror ($D\geq10\,$m) that would survey the Northern sky.
We propose a new photometric instrument observing at mm wavelengths and located at the Teide Observatory, in Tenerife, with latitude $+28^\circ$ at 2400 meters of altitude. Such instrument would be placed on a 13-meter diameter antenna and would observe at four different bands: 90, 150, 220 and 260 GHz (3, 2, 1.4 and 1.15 mm, respectively) with $\leq1^\prime$ resolution. The field-of-view would cover 1 degree, with more than 70k KID detectors in several different arrays.
In this talk we present a new set of simulations to assess the capabilities of the instrument with regard to galaxy cluster and SZ science. We generate realistic distributions of clusters, and include noise levels (with $1/f$ and white components) consistent with those expected at the Tenerife site. We also generate point source maps and an appropriate transfer function in order to accurately account for the expected filtering from the instrument. We consider two related scenarios: wide (WS) and deep (DS) surveys, accounting for 6000 and 300 deg$^2$ and observing for 3 years each with 50% time efficiency. We present the expected sensitivity of the instrument in all four previous bands, the forecasted performance for blind searches of galaxy clusters and its ability to recover both their thermal and kinematic components.
Cross-correlation/stacking analyses of Sunyaev-Zeldovich observations and galaxy surveys offer a promising method for studying properties of the gas reservoirs surrounding galaxies and the astrophysics that govern their evolution. These statistical studies can be used to constrain models and simulations through a detailed forward model, but the implementation and systematics of constructing a predicted signal can introduce significant sources of error into the results. We discuss the effects of survey modeling such as Halo Occupancy Distributions in the forward model and its relevance to the current discrepancy between simulations and observations, and present some early results using new data and simulations with our improved pipeline.
The Millimeter Sardinia radio Telescope Receiver based on Array of Lumped elements kids is (MISTRAL) is a novel high resolution, wide field of view millimeter camera currently installed at the Sardinia Radio Telescope (SRT), a 64 m fully steerable gregorian radio telescope located in Italy. MISTRAL was developed in the framework of the SRT-HighFreq project, funded by a National Operational Program (PON), with the aim to expand the capabilities of the radio telescope in order to cover frequency up to the W band. The 90 GHz sky has been extensively studied by Cosmic Microwave Background experiments, both ground-based (ACT, SPT, and others) and satellite-based (WMAP, Planck). However, their resolution is limited to ~1’ from ground telescopes and ~10’ from satellite. With this new instrument, we aim to observe the microwave sky at a resolution of ~12’’ with a high mapping speed, a capability only shared by few instruments in the world, unlocking the exploration of a plethora of science cases from the recently upgraded SRT. These science cases span from observations of the Sunyaev-Zel’dovich effect in clusters and other large scale structures in the universe, to galactic science and solar system science.
The heart of MISTRAL is a ~100 mm silicon focal plane populated with 415 cryogenic Lumped Elements Kinetic Inductance Detectors (LEKIDs). These detectors are copuled with the telescope using a cold (4K) re-imaging optical system composed of two silicon lenses, producing a diffraction limited field of view of 4’. The system is enclosed in a custom cryostat, built with strict requirements on its size, in order to fit on the rotating turret that allows to switch the receivers to be quickly moved in and out of the gregorian focus position.
After the successful installation on the telescope in may 2023, MISTRAL started its technical commissioning in the early 2024. In this contribution we will give an overview of the MISTRAL instrument and its subsystems, and report their performances during the technical commissioning phase.
Galaxy clusters are the largest gravitationally bound structures in the Universe, making them critical probes for cosmology. The distribution of clusters across mass and redshift allows us to constrain cosmological parameters such as the growth of structure, the total neutrino mass, and the matter density fraction. Accurate cluster mass measurements and calibrations of mass-observable scaling relations are essential in this process. In the first part of my poster, I will briefly show my recent work (Saha et al. 2023, arXiv:2307.11711) and discuss prospects for studying high-redshift clusters using CMB lensing with upcoming experiments like CMB-S4. In the second part, I will explore targeted observations of low- to mid-redshift clusters via NASA’s balloon-based imaging telescope, SuperBIT, where I am currently working on the shape-measurement pipeline and convergence map making from its shear observations.
Galaxy cluster scaling relations are fundamental for understanding cluster physics and testing ΛCDM, but their use in cosmology is still limited by large uncertainties. Many studies rely on hydrostatic equilibrium, despite numerous out-of-equilibrium systems, and the classification of cluster dynamical states remains incomplete, particularly for intermediate evolutionary stages. Even gravitational lensing, the only mass measurement independent of equilibrium assumptions, is affected by projection effects, especially in unrelaxed clusters.
We present a new approach based on dark matter-gas coherence, which quantifies how well the intracluster gas traces the mass distribution. We tested this method on simulated clusters (IllustrisTNG300), demonstrating a strong correlation between coherence and scatter in scaling relations, offering a way to improve cosmological constraints. Additionally, we applied the method to a small sample of observed clusters, showing its feasibility for real data.
By addressing both hydrostatic equilibrium biases and weak lensing projection effects, this method provides a powerful tool to classify cluster dynamical states more systematically and reduce systematic uncertainties in cluster-based cosmology.
Galaxy clusters are powerful probes of the large-scale structure of the universe and cosmology, with their population statistics being highly dependent on the expansion history of the universe and growth of structure. In the last few decades, galaxy cluster samples across wavelengths have exceeded thousands of objects, including those identified in the millimeter regime through the use of the thermal Sunyaev-Zeldovich (tSZ) effect. This has opened the door to using the 2-point clustering statistic of galaxy clusters to place constraints on cosmology and the tSZ mass-observable scaling relationship in ways that are complementary to the existing 1-point cluster abundance statistic measurements.
In this talk, we will present the first measurement of clustering with tSZ-selected galaxy clusters using the 5-year, 1500 square degree galaxy cluster catalog from SPT-3G. We will also discuss the constraining ability of this sample with regards to astrophysical and cosmological parameters.
We present an open source Python package to compare simulation-based inference (SBI) approaches to MCMC inference in the context of galaxy cluster mass estimates from gravitational weak lensing data. The package, CLSBIWeakLens, provides a modular framework to flexibly run numerical experiments on cluster mass estimation from radial profiles, a typical data vector in optical cluster cosmology from surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). CLSBIWeakLens has modules to define the ‘simulations’ used to train the SBI, modules to build the inference procedures, and a straightforward interface for the user to create new experiments through user-defined configuration files. Our framework allows for testing the robustness of inference posteriors to noise in the data, approaches to stack data vectors to average out the noise, and modeling choices for population statistics and the mass distribution within each galaxy cluster. We illustrate example experiments that we lay out in tutorials, highlighting (1) tests on the effects of noisy data on posteriors with inference performed on stacked radial profiles and on individual radial profiles, and (2) tests on inference performed with a misspecified model. This framework provides foundations to the potential application of SBI to speed up inference in hierarchical models for galaxy cluster cosmology. The source code is publicly available on GitHub.
State-of-the-art cosmic microwave background (CMB) telescopes must deploy receivers with a high density of superconducting detectors. Reading out these detectors while maintaining cryogenic conditions requires novel multiplexing schemes. Microwave superconducting quantum interference device multiplexing has been shown to achieve multiplexing factors on the order of 1,000, which is a drastic improvement over previous technologies. Non-linear and time-variable crosstalk between detectors due to this readout system, however, may introduce a new systematic CMB map-level effect. As this readout system has recently been deployed to the Simons Observatory to enable the readout of its more than 60,000 detectors located at 5,200 m on Cerro Toco in Chile’s Atacama Desert, it is necessary to characterize the potential biases from a systematic crosstalk effect. This contribution will present large-scale simulations of this crosstalk effect in the Simons Observatory large-aperture telescope (LAT), which contains more than 30,000 of the observatory’s detectors. The weak lensing signal from the LAT will unlock a wealth of information about the Universe by measuring the growth of structure, constraining cosmological parameters, and limiting the sum of the masses of neutrinos. These simulations will be used to better understand necessary crosstalk mitigation techniques for reconstructing the CMB’s weak lensing power spectrum as measured by this new instrument so that its science goals are achieved.
The Simons Observatory (SO) consists of one large aperture and three small aperture telescopes currently operating in four frequency bands between 90-280 GHz, located at ∼5,200m altitude in the Atacama Desert of Chile. SO is dedicated to observing the polarized cosmic microwave background (CMB), among other science goals, with the primary focus of the small aperture telescopes (SATs) being to constrain the primordial B-mode polarization signal. The SATs, each containing ~10,000 detectors, utilize a cryogenic continuously rotating half-wave plate (CHWP) consisting of a sapphire stack and superconducting magnetic bearing. The CHWP spins at frequency 𝑓~2Hz and aims to mitigate the atmospheric noise and systematic uncertainties to recover the large-scale CMB polarization signal. The second harmonic of the HWP rotation frequency (2𝑓 at 4 Hz) has a contribution from differential transmission that is linearly correlated with atmospheric temperature. Therefore, we can fit the 2𝑓 signal with measured precipitable water vapor (PWV) for values below 3mm. Since the 2𝑓 signal is independent of the polarization modulation, which occurs at 4𝑓, the 2𝑓 signal may be a useful calibration method. We explore this method as a possible relative calibration between detector responsivities, as well as overall detector responsivity over different seasons of observations.
Spatially and spectrally resolved observations of the thermal and kinematic Sunyaev-Zel’dovich (SZ) effect towards galaxy clusters are crucial for understanding their formation and assembly history. Current instrumentation for direct observations of the SZ effect in the mm/submm rely either on coherent receivers or on imaging cameras. Coherent receivers can achieve a high spectral resolution, but have a limited field of view and spectral bandwidth. Cameras, on the other hand, offer a large field of view and spectral bandwidth, but lack the spectral resolution. This dichotomy manifests itself in a gap in parameter space between coherent receivers and cameras and highlights the need for a novel mm/submm spectral imager that combines the advantages of both concepts.
We present the Terahertz Integral Field Unit with Universal Nanotechnology (TIFUUN) instrument, a mm/submm on-chip integral field unit designed to fill the gap between coherent receivers and imaging cameras. The instrument uses a wideband lens-antenna array, a superconducting filterbank, and microwave kinetic inductance detectors (MKIDs), to spectrally image cosmological volumes with a large field of view of around 7.6 arcminutes, a spectral bandwidth spanning one to two octaves, and moderate spectral resolution from R=100 up to R=1000. The first prototype, which will be optimized for observing the spatially and spectrally resolved SZ effect, is currently being designed and developed for use at the ASTE telescope. Recently, we have successfully performed the commissioning and science verification campaign of the DESHIMA 2.0 instrument at ASTE, which is essentially a single-pixel TIFUUN. This further motivates TIFUUN as a valuable instrument for galaxy cluster science, and for mm/submm astronomy in general.
Crucial in the design procedure for TIFUUN is TiEMPO2, a software program for the simulation of realistic time-ordered data streams for TIFUUN observations at arbitrary telescopes. TiEMPO2 uses a dynamic model of the atmosphere to model the radiative transfer of an arbitrary astronomical source. Noise is calculated and added real-time using a realistic photon noise and two-level system noise model. The code can be used through a Python interface, and is powered by libraries written in C++ and CUDA. These simulations will be used to optimize the TIFUUN chip design for the SZ observations, but will also be used to test data reduction pipelines and noise reduction techniques.
The Atacama Cosmology Telescope (ACT) conducted an arcmin resolution survey of the southern sky at millimetre wavelengths from 2008-2022. In this talk I will present an update on the ACT search for galaxy clusters using the redshift independent Sunyaev-Zel'dovich (SZ) effect, using data from the full ACT survey, covering 15,000 square degrees. The final ACT Data Release 6 (DR6) cluster catalog is expected to include more than 9,000 galaxy clusters with redshift and mass estimates. I will describe the construction of the catalog (in particular the differences with respect to ACT DR5), products and tools associated with the data release, and discuss some science applications of the catalog.
The South Pole Telescope (SPT) is a 10-meter millimeter-wavelength telescope located at the geographic South Pole, one of the world’s premier sites for millimeter-wave observations. The SPT has been used to conduct several generations of wide-field high resolution cosmic microwave background (CMB) surveys including the 2500-square-degree SPT-SZ survey, the SPTpol 500d and ECS surveys, and the SPT-3G survey. One of the primary objectives of these surveys has been the construction of mass-limited samples of galaxy clusters identified via the thermal Sunyaev- Zel’dovich (SZ) effect, through which massive clusters imprint subtle temperature distortions on the CMB. The abundance of such clusters is a powerful cosmological probe as it depends sensitively upon both the expansion history of the universe and the growth of density fluctuations. In this talk I will discuss progress in the construction of the SZ cluster samples from SPT-3G, particularly focusing on results from the main survey for which over 6,000 SZ clusters are expected in the 1500-square-degree survey.
The abundance of galaxy clusters, the clustering of galaxies, and weak gravitational lensing are key observables of the cosmic large-scale structure. Over the past decade, tremendous progress was made in obtaining high-precision measurements, notably thanks to sensitive wide-field surveys of the cosmic microwave background and of galaxies and gravitational lensing. The abundance of clusters selected in data from the South Pole Telescope (SPT) — in combination with mass calibration based on weak-lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope — was shown to be compatible and complementary with analyses of galaxy clustering and weak lensing (3x2pt).
In my talk, I will review the SPT cluster cosmology program and discuss our results from lensing-informed abundance measurements. Building on this latest SPT analysis and on galaxy and shear two-point correlation function measurements in DES Year 3 data, I will present cosmological constraints from the joint analysis of these probes (SPT clusters + DES 3x2pt). The precision of these results highlights the benefits of multiwavelength multiprobe cosmology and our analysis paves the way for upcoming joint analyses of next-generation datasets.
Galaxy clusters, representing the peaks in the cosmic density field, serve as an independent and powerful tool for investigating the evolution of cosmic structures. The strategic identification of these clusters through multi-wavelength surveys is essential for advancing our understanding of gravitational theory, general relativity, and cosmological models. A significant milestone was achieved with the successful launch of eROSITA in July 2019. The German-built eROSITA X-ray telescope, on board the Russian-German Spectrum-RG (SRG) mission, operates within the 0.2-8 keV range and has produced the largest ICM-detected catalogs of galaxy clusters and groups through its first All-Sky Survey. With over 10,000 cluster candidates, the survey is pivotal in refining cosmological parameters when combined with the data from optical surveys like DESI Legacy, DES, HSC, and KIDS. These parameters are constrained at a percentage level through the evolution of the cluster mass function, representing a significant leap forward. In this talk, I will outline the constraints on fundamental cosmological parameters and neutrino masses derived from the first eROSITA All-Sky Survey. Additionally, I will present eROSITA's significant detection of warm baryons within cosmic filaments and the implications for our understanding of AGN feedback in group-size haloes. I will summarize the value-added products made available to the science community by the eROSITA consortium's data release.
The large-scale structure of the universe can be probed by different observables. Galaxy clustering, weak gravitational lensing, galaxy cluster abundances, and cluster clustering are each sensitive to different aspects of cosmic structure formation and are affected by different astrophysical and observational uncertainties. Consistency of different observables presents a strong test of our cosmological model. Further, combinations of all observable lead to the most precise and accurate constraint. In this talk, I will present the cosmological constraints from cluster abundances and auto/cross-correlations of clusters, galaxies, and lensing measured from the Dark Energy Survey. I will discuss the implications of the result and prospects for the Euclid, Rubin, and Roman era.
The Euclid mission is designed to map the geometry and growth of structure in the Universe with unprecedented precision. As part of this effort, galaxy clusters serve as a crucial probe for constraining cosmological parameters, thanks to their sensitivity to both the expansion history and the growth of cosmic structures.
In preparation for the exploitation of Euclid’s cluster samples, extensive work has been carried out on simulations. I will discuss key aspects of this preparatory effort, including likelihood modelling, the mass function, bias calibration, and the selection function, all of which are essential for robust cosmological constraints. These studies provide a solid foundation for the analysis of the first Euclid data.
With the first Euclid data release (Q1), the Galaxy Cluster working group has now begun detecting and characterising clusters, marking the first step towards precise cosmological measurements. I will present these initial results and discuss the challenges and next steps in harnessing Euclid’s full potential for cluster cosmology.
Clusters of galaxies, formed at the latest stages of structure formation, are unique cosmological probes to study the formation and evolution of large-scale structures. With the advent of large CMB surveys like those from the Planck satellite, the ACT and SPT telescopes, we now have access to large catalogs of galaxy clusters detected at millimeter wavelength via the thermal Sunyaev-Zeldovich (tSZ) effect. Nevertheless, it is interesting to complement them with high angular resolution (tens of arcseconds) observations to target the lowest mass and highest redshift clusters. This is the case of observations with the NIKA2 camera, which is installed on the IRAM 30–m telescope in Pico Veleta, Spain. Combining a 6.5 arcmin diameter field of view and sub-arcminute (17.6'' at 150 GHz) angular resolution, NIKA2 is capable of resolving the SZ effect towards clusters up to high redshifts.
In this talk, I will highlight NIKA2’s capabilities in unveiling low-mass, high redshift clusters. I will focus on the blind detection of galaxy clusters in the COSMOS field using the NIKA2 Cosmological Legacy Survey (N2CLS) Large Program observations. I will describe the candidate cluster sample we have obtained, and discuss its properties.
I will demonstrate that NIKA2 and the IRAM 30–m telescope are sensitive to the lowest mass clusters at intermediate and high redshift.
The multi-component matched filer (MCMF) cluster confirmation framework, designed to leverage the synergies between ICM-selected cluster surveys and optical imaging surveys, has been applied to some of the largest and high-quality surveys to date with a focus on high purity and well controlled cluster samples for cosmological purposes. MCMF confirmed cluster catalogs have subsequently been used for the eROSITA-based eFEDS cluster cosmology as well as for the most recent cosmological results from SPT.
Besides a general overview of the MCMF family of cluster catalogs, I will present results and current status of several science projects based on ACT-DR5 MCMF and RASS-MCMF catalogs, currently the largest SZ and second-largest X-ray cluster catalogs available. Key topics include CMB lensing from galaxy clusters, cluster-based void samples, and cluster cosmology with samples of approximately 5,000 clusters, representing a fivefold increase over our most recent SPT-based cosmological analysis.
I will conclude with results from a pilot study applying MCMF to the latest dataset from the Euclid mission (Q1), demonstrating its potential for cluster confirmation at high redshifts. These findings provide an outlook on how Euclid will significantly improve the ability to confirm high-redshift clusters expected from next-generation SZ surveys, such as SPT-3G and the Simons Observatory.
We present a catalog of 500 galaxy cluster candidates in the SPT-Deep field: a 100 square-degree field that combines data from the SPT-3G and SPTpol surveys to reach noise levels of 3.0, 2.2, and 9.0 uK-arcmin at 95, 150, and 220 GHz, respectively. This is comparable to noise levels expected for the wide field survey of CMB-S4, a next-generation CMB experiment. Candidates are selected via the thermal Sunyaev-Zel'dovich (SZ) effect with a minimum significance of SNR = 4.0, resulting in a catalog of purity $\sim 89 \%$. Optical data from the Dark Energy Survey and infrared data from the Spitzer Space Telescope were used to confirm 440 cluster candidates. The clusters span 0.25 < z < ~1.8 and 1e14 Msun/h < M500c < 8.8e14 Msun/h. The sample's median redshift is 0.75 and the median mass is 1.66e14 Msun/h; these are the lowest median mass and highest median redshift of any SZ-selected sample to date.
We assess the effect of infrared emission from cluster member galaxies on cluster selection by performing a joint fit to the infrared dust and tSZ signals by combining measurements from SPT and overlapping submillimeter data from Herschel/SPIRE. We find that at high redshift (z>1), the tSZ signal is reduced by ~17% (~4%) at 150 GHz (95 GHz) due to dust contamination. We repeat our cluster finding method on dust-nulled SPT maps and find the resulting catalog is consistent with the nominal SPT-Deep catalog, demonstrating dust-contamination does not significantly impact the SPT-Deep selection function; we attribute this lack of bias to the inclusion of the SPT 220GHz band.
Galaxy clusters are the largest gravitationally bound objects in the Universe, serving as powerful cosmological probes on the growth of structure on the largest physical scales. The thermal Sunyaev-Zeld'dovich (tSZ) effect is now a well-established technique for probing the intracluster medium (ICM) of galaxy clusters on these scales. Measuring the gas pressure serves as a robust tracer of mean ICM structure, as variations in gas temperature will be counteracted by changes in gas density. The generalized Navarro–Frenk–White (gNFW) model is a strong descriptor of average cluster pressure for a large range in cluster mass and redshift.
We will present our findings on measuring average gNFW pressure profiles for the SPT-SZ cluster sample, containing 516 clusters over a large range in both mass and redshift. We use both SPT-SZ and Planck survey data, constraining cluster pressure from intermediate to high radii. We also explore the average cluster profiles for morphologically different samples, such as cool core, non-cool core, relaxed, and disturbed. Two of the key findings in the work are a strong indication of lower average pressure in the universal pressure profile fit at high radii, and a significant disparity in pressure profiles between the relaxed and disturbed subsamples.
In a self-similar paradigm of structure formation, the thermal pressure of the hot intra-cluster gas follows a universal distribution independent of the mass scale. Thus, this thermal pressure distribution is universal in every cluster once normalised to the proper mass and redshift dependencies. The reconstruction of such a universal pressure profile requires an individual estimate of the mass of each cluster. In this context, I will present a method to jointly fit the universal pressure profile and individual cluster masses over a sample of galaxy clusters, properly accounting for correlations between the profile shape and amplitude, and masses scaling the individual profiles. I will investigate the propagation of the uncertainties on the fitted masses and profiles onto the SZ power spectrum and subsequently on the cosmological parameters. I will present the results of the application of this framework to a subsample of 28 CHEX-MATE clusters.
The millimeter part of the spectrum is one of the least explored parts of a galaxy's spectral energy distribution (SED), yet it contains emissions from three fundamentally important physical processes: the thermal emission from dust, the free-free emission from ionized gas, and the synchrotron emission from relativistic charged particles moving in the galactic magnetic field.
During my presentation, I will give an in-depth description of the millimeter emission of the face-on spiral galaxy NGC 4254, which is part of the IMEGIN Large Program (Interpreting the millimeter Emission of Galaxies with IRAM-NIKA2; PI S. Madden) targeting 22 nearby galaxies in the millimeter continuum regime with the NIKA2 camera, mostly focusing on the interstellar dust component.
Specifically, I will show as the new millimeter data, combined with a suite of observations at other wavelengths (including metallicity measurements and CO and HI line intensity maps), were crucial to: put constraints on the FIR-mm SED of the galaxy and, consequently, on the dust mass content and the dust FIR slope; disentangle from dust contribution, free-free and synchrotron emission in the millimeter regime; constrain the dust-to-gas mass ratio, which provides a direct link to the galaxy chemical evolution and the reservoirs for dust production; study the microscopic properties of dust and their variation with the ambient conditions (in terms of density, temperature and metallicity of the inter-stellar medium); investigate the relation between dust and star formation in spiral arms, inter-arms regions, nuclear region, and on a global scale. These results were achieved by modeling the galaxy IR-to-radio SED, both on global and spatially resolved scales, using the hierarchical Bayesian fitting code HerBIE (Galliano et al. 2018), which includes the prescriptions from the dust evolution model THEMIS (Jones et al. 2017).
The NIKA2 dual-band camera at the IRAM 30-meter telescope was used to
obtain maps of the 1 mm and 2 mm dust emission in four regions of the
nearby filaments of Taurus and Perseus. These regions encompass more
than a dozen of dense cores at different stages of evolution in the
process to form stars. The NIKA2 data are combined with published maps
of the dust temperature and of optical extinctions derived from
Herschel maps allowing to study changes of the dust emissivity index
at mm wavelengths with column densities and environment. The observed
indices are then compared with models of grain coagulation and the
build-up of ice mantles.
Polarized dust emission is one of the major foreground contaminants in CMB data. With increasing sensitivity and resolution in new CMB experiments, we need dust models in polarization that reflect the data both at large and small angular scales. In this talk, I will present new polarized dust maps using Planck PR4 data which improve on the existing GNILC PR3 maps.
The Planck satellite maps of the polarized sky spanning frequencies from 30 to 353 GHz (i.e. 10 mm to 850 $\mu$m) had a profound impact on our understanding of both cosmology and the interstellar medium. While the submillimeter bands at 545 and 857 GHz (550 and 350 $\mu$m respectively) were not originally designed for polarimetry, the ground calibration campaign suggested a residual polarization sensitivity at the few percent level. At 857 GHz in particular, the polarized Galactic dust emission is sufficiently bright to be detected in Planck data despite the minute polarization sensitivity, provided adequate control of systematic effects is achieved. In this talk, I will present the reconstruction of polarization maps from Planck 857 GHz observations building on the NPIPE reprocessing framework, with particular emphasis on efforts to refine ground calibration measurements and to model and mitigate key systematic effects, such as far sidelobes and bandpass mismatch. I will conclude by presenting the dust properties inferred from our analysis of the polarized 857 GHz emission, including its correlation with the polarized 353 GHz emission, and discuss their implications for foreground removal in cosmic microwave background B-mode searches.
Foreground emission from the Galaxy presents a major challenge for microwave experiments aiming to detect cosmic signals. In particular, polarized Galactic emission remains a major obstacle to precise measurements of the cosmic microwave background (CMB) polarization, such as the inflationary B-mode signal. To tackle these issues, the Pan-Experiment Galactic Science Group PySM Collaboration has developed a publicly available suite of all-sky Galactic microwave emission and polarization models at sub-arcminute scales. These new models are built using a polarization fraction tensor framework and incorporate the latest observational data from large-area surveys. By combining well-measured large-scale emission with realizations of small-scale synthetic emission, they generate dust and synchrotron foreground maps that are statistically consistent yet stochastic at small scales, while aligning with observational data at large scales. To support CMB experimental design, forecasting and analysis, we provide three coherent model suites — low, medium, and high complexity — spanning the range of astrophysical complexity permitted by current data. In this talk, I will discuss the construction of these new PySM models, demonstrate their overall improved agreement with observational data compared to previous models, and outline their future prospects.
As we enter a golden age of data-driven cosmology, multi-wavelength surveys are set to revolutionize our understanding of the universe. Ongoing and upcoming observations - ranging from Sunyaev-Zel'dovich (SZ) effects to X-ray emissions, fast radio bursts (FRBs), and absorption line studies — promise unprecedented insights into the astrophysical processes driving galaxy formation and evolution, the impact of baryonic physics on cosmological observations, and the fundamental parameters of our universe. In this talk, I will explore key insights derived from CAMELS simulations and outline a strategic roadmap for optimizing scientific returns from these surveys. By integrating simulation data with advanced machine learning techniques, we can enhance our interpretations and guide future research directions in precision cosmology and galaxy astrophysics.
The Three Hundred Simulation Suites include 324 re-simulated regions identified around massive clusters and resimulated with different hydrodynamical codes and resolution. Their purpose is to provide a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications. Extensive work has been done to create mocks images to compare with observations and catalogs of simulated clusters have been extracted to match the characteristics of observed samples, such as NIKA2 and CHEX-MATE. I will give an overview of the products at disposal to the community, provide information on how to access them, discuss some comparison between the results of the hydrodynamical codes, and present how the simulations helped with both the analysis and the interpretation of observed data.
Including millimeter-wave (mm-wave) data in multi-wavelength studies of the variability of active galactic nuclei (AGN) can provide insights into AGN physics that are not easily accessible at other wavelengths. We will discuss the potential of cosmic microwave background (CMB) telescopes to provide long-term, high-cadence mm-wave AGN monitoring over large fractions of sky. The South Pole Telescope (SPT) group has launched an AGN monitoring campaign using data from the SPTpol and SPT-3G instruments, providing high-cadence long-baseline light curves that span from 2012 to present day.
I will review what we know about mm-wave selected dusty galaxies: their composition, redshift distribution, and spectral properties. I will review the latest observations from ALMA and JWST. I will present an overview of current and planned blank-field surveys. I will discuss prospects for characterizing the population with future facilities in the coming decades.
The South Pole Telescope (SPT) is at the frontier of measuring the cosmic microwave background and surveying the millimeter sky. The third-generation SPT camera (SPT-3G) has observing frequencies centered at 90, 150, and 220 GHz (3.3, 2, and 1.4 mm) and arcminute resolution, enabling the study of millimeter-bright astrophysical objects. In this work, we present the static, emissive point source catalog from roughly 1,500 square degrees observed from 2019-2023 and associated source counts. We detected ~28,000 objects with signal-to-noise of at least five (> 5σ) in one or more bands, corresponding to 1.2, 1.4, and 4.6 mJy at 90, 150, and 220 GHz, respectively. This SPT-3G catalog is the largest and deepest source catalog in the millimeter bands to-date. Comparisons to external catalogs in radio, infrared, and millimeter frequencies leave ~14,000 SPT-3G sources (50% of the catalog) without counterparts at other wavelengths or in a previous millimeter survey. The spectral indices of the sources reveal two populations: flat- and falling-spectrum sources indicating synchrotron radiation from active galactic nuclei (AGN, ~12,000 sources) and rising-spectrum sources corresponding to thermal emission from dust-enshrouded galaxies (~16,000 sources). Our high-redshift dusty star-forming galaxy (DSFG) selection process results in ~4,000 candidates detected at > 5σ in both the 150 and 220 GHz bands. Prior small samples of SPT-selected dusty galaxies have a mean redshift of z~4; a sample of thousands of these objects from SPT-3G will enable exciting studies of early universe galaxy formation and evolution, and probes of high-redshift structure.
Abstract: Information about the late-time Universe is imprinted on the small-scale CMB as photons travel to us from the surface of last scattering. Several processes are at play and small-scale fluctuations are very rich and non-Gaussian in nature. I will review some recent and exciting results that use the Sunyaev-Zel'dovich (SZ) effects and gravitational lensing to paint a full picture of the visible and dark matter in and around DESI galaxies. I will discuss how a combination of measurements can probe velocity fields at cosmological distances and inform us on galaxy energetics. I will also show recent measurements of weak lensing of the CMB and its cross-correlation with DESI, and how they can help us interpret intriguing discrepancies in cosmological parameters between the high and low redshift Universe.
As cosmic microwave background photons travel through the Universe a small fraction of them interact with the intervening cosmic gas and thereby imprint the properties of this gas on our CMB observations. In this talk I will describe how data from the Atacama Cosmology Telescope can be used to isolate the signals arising from hot gas throughout the Universe and how the data can be used to measure both the integrated electron pressure and temperature of galaxy clusters. I will discuss how upcoming CMB experiments, such as the Simons Observatory, will allow us to improve our characterisation of the properties and evolution of cosmic gas.
One of the most powerful tests of our cosmological model and of new physics is to determine the growth of large-scale structure with time. Motivated by this and by reports of tensions in structure growth, in the first part of my talk I will show state-of-the-art determinations of cosmic structure growth using CMB gravitational lensing measurements from the Atacama Cosmology Telescope (ACT), in auto-correlation and cross-correlation with unWISE galaxies. I will discuss the implications of our ACT DR6 lensing results for the validity of our standard cosmological model as well as for key cosmological parameters.
I will also present first measurements of a new probe of large-scale structure and the early universe: the cosmic velocity field reconstructed from the kinetic SZ (kSZ) effect. After showing our early measurements of this signal with ACT, I will discuss ongoing efforts to reconstruct the velocity field at increasingly high precision with this new technique, and I will explain why kSZ velocity reconstruction may be the key to systematics-free measurements of primordial non-Gaussianity from large-scale structure.
The South Pole Telescope (SPT), a 10-meter telescope optimized for observing the primary and secondary anisotropies of the cosmic microwave background (CMB), is currently equipped with the SPT-3G camera. The high angular resolution and low noise maps produced by SPT-3G are ideally suited for reconstructing the CMB lensing potential, mapping matter distribution to high redshifts, and probing fundamental physics. This talk presents results from the SPT-3G lensing analysis using data from 1500 deg² over the Southern Sky collected during the 2019 and 2020 seasons. Our analysis employs the improved global minimum variance estimator, reducing noise by up to 10% compared to the standard quadratic estimator and achieving a statistical uncertainty on the lensing amplitude of about 2%. The resulting map, the deepest to date, is signal-dominated out to L ~ 400, with significant contributions from polarization. This high-sensitivity map will provide critical insights into cosmic structure growth and neutrino masses. We plan to cross-correlate this map with external datasets to extract cosmological and astrophysical information and use it to delens BICEP/Keck data, thereby sharpening constraints on primordial gravitational waves. This analysis marks significant progress in CMB lensing measurements, which have evolved from early detections to one of the most powerful cosmological tools in less than two decades.
The kinetic Sunyaev--Zel'dovich kSZ effect is sourced by CMB photons scattering off of moving electron gas, and contains information on gas density as well as velocity. Through the velocity dependence, this signal contains information about cosmology on the largest scales. By combining a CMB map with a galaxy survey to measure where the electrons are, the velocity information can be isolated in a technique known as kSZ velocity reconstruction. I will talk about the measurement of the effect with ACT DR6 data in combination with the DESI Legacy survey LRGs, discuss constraints on cosmology, and talk about future constraints on non-Gaussianity from SO data in combination with LSST.
Mapping the distribution of baryonic mass in our Universe down to the group-sized halo masses it is essential to clarify how much baryonic matter is locked up in halos and in filaments. Non-gravitational processes affect the thermodynamical conditions of the hot gas and baryonic content of groups and clusters of galaxies, causing deviations from the theoretical self-similar expectations. Indeed, many observational studies advocate a thermal feedback (such as the one provided by black holes residing in central galaxies) to explain their findings on the hot gas and overall baryonic content. Combined X-ray and optical data can allow us to investigate these features down to group scales, thanks to the unprecedented sensitivity reached by state-of-art telescopes in X-ray (i.e. eROSITA) and spectroscopic optical surveys such as SDSS, GAMA and WEAVES. In order to provide a fair comparison and be able to address the possible observational biases, we design a multiwavelength lightcone extracted from cosmological hydrodynamical simulations. We mimic the observational conditions and generate synthetic datasets that closely resemble the observations of galaxies in cluster/group-size halos. The lightcone incorporates the effects of various physical processes, including gas dynamics, feedback and several sources of contaminants. By combining the X-ray and optical properties of galaxies in the simulations, we can explore the hot gas on both large-scale structure and the galaxy population. In conclusion, I will present the results of this analysis which poses the foundations for future studies devoted at addressing all these observables.
Optically identified galaxy clusters have the potential to provide some of the most precise cosmological constraints, as they enable the detection of lower-mass clusters. However, they are also highly susceptible to systematic effects, with projection effects being a major challenge. This misidentification of member galaxies introduces anisotropies in the observed distribution of optical clusters, which can bias cosmological analyses. Fortunately, these anisotropies can be constrained through the three-dimensional cluster clustering, which also provides information about velocity fields through redshift-space distortion. In this talk, I will discuss a framework for modeling 3D clustering in optical clusters while accounting for projection effects, highlighting how this approach can mitigate systematics and enhance the robustness of optical cluster cosmology.
We study the robustness of a simulation-based inference (SBI) method in the context of cosmological parameter estimation from galaxy cluster abundance in mock cluster datasets. I will describe an application where we train an SBI model, based on a mixture density network (MDN), to derive posteriors for cosmological parameters from a stacked cluster data vector constructed using an analytic model for the galaxy cluster halo mass function. We compare the SBI posteriors to posteriors from an equivalent MCMC analysis that uses the same analytic form for the likelihood. Although this idealized analysis is designed for optical surveys, we have learned that the SBI method can be an effective method for galaxy cluster cosmology analysis and their results are highly consistent with those derived from the MCMC method. I will describe the results from the SBI and MCMC analyses and the lessons learned from the comparison.
Galaxy cluster abundance measurements serve as a powerful probe for constraining cosmological parameters such as the matter density ($\Omega_m$) and the amplitude of density fluctuations ($\sigma_8$). Wide-area surveys detect clusters using observables like the thermal Sunyaev-Zeldovich (SZ) effect, a spectral distortion in the Cosmic Microwave Background (CMB). Accurate cosmological constraints require precise characterization of the survey selection function, which, in SZ surveys, is typically defined by the probability of detecting a cluster based on its total SZ signal and angular scale.
In this talk, we investigate the impact of triaxiality and orientation on the selection function of the Planck SZ survey. Employing a Monte-Carlo method, we inject triaxial cluster profiles at random positions within the Planck all-sky maps and subsequently detect them using the Multi-Matched Filtering Planck algorithm (MMF3). Our analysis reveals that cluster orientation significantly affects detection probability: for a given total SZ signal and angular size, clusters elongated along the line of sight are more likely to be detected. This results in a systematic upward bias in the derived Weak Lensing (WL) mass estimates of SZ selected clusters relative to cluster samples with random orientations, with bias values as high as 5% for clusters near the low-mass limit of the survey. Given the percent-level mass calibration requirements of upcoming cluster surveys, quantifying such biases is critical for precision cosmology.
Galaxy clusters serve as powerful cosmological probes through number count analysis. Beyond that, the gas distribution in cluster outskirts provides a model-independent method for deriving competitive cosmological constraints. By combining HIGHMz—a subsample of 32 of the most massive CHEX-MATE clusters—with X-COP clusters, this study derives robust and precise constraints on the matter density and Hubble parameter using four independent methods: gas mass fraction, the ratio of SZ to X-ray pressure, the size-temperature relation, and the universality of the emission measure profile. Crucially, this analysis is designed to be resilient to traditional assumptions and systematics related to baryons, eliminating the need for simulation-based calibrations. The findings will offer valuable insights for the cluster community over the next decade, enhancing our understanding of matter distribution in galaxy groups and clusters and their broader cosmological implications.
Independent constraints on the Hubble constant ($H_0$) from local distance ladders and early Universe CMB data can be derived from cluster sizes by combining X-ray and millimetre observations of the intracluster medium. Using XMM-Newton and Planck data, we present the inference on $H_0$ by studying systematic mismatches, $\eta_T$, between X-ray and millimetre temperature (or pressure) estimates: $T_{X-ray} = \eta_T P_{SZ}/n_{e, X-ray}$. However, cosmology is only one of the factors influencing $\eta_T$. Several astrophysical and observational systematics contribute to this discrepancy, including assumptions regarding the cluster structure, such as spherical symmetry, clumpiness, as well as the chemical composition of the ICM, or the neglect of relativistic effects in the SZ signal. To systematically account for all these effects, we employ a Bayesian approach, comparing observational data with numerical simulations from The Three Hundred project. This framework is applied to the CHEX-MATE sample, consisting of 116 clusters of Planck-selected systems. Additionally, we evaluate the impact of relativistic corrections to the SZ signal on thermodynamic profiles and their effect on the inferred value of $H_0$.
The NIKA2 Cosmological Legacy Survey (N2CLS) observed the GOODS-N and COSMOS fields with the NIKA2 millimeter camera at the 30m IRAM telescope on the Sierra Nevada.
On behalf of the N2CLS team, I will present the survey and its early results. The deep GOODS-N NIKA2 maps are close to the photometric confusion limit in both the 2.0 and 1.2 millimeter bands. A total of 120 and 67 sources in the 159 arcmin2 GOODS-N and 301 and 124 sources in the 1010 arcmin2 COSMOS maps are detected at 1.2 and 2.0 mm, respectively.
Number counts are defined with unprecedented precision and are compared, along with galaxy colors, to the predictions of the Simulated Infrared Dusty Extragalactic Sky (SIDES).
The NIKA2 GOODS-N catalog was matched to the rich multi-wavelength data set available from the X-rays to radio frequencies, including Chandra, JWST, HST, Spitzer, Herschel, VLA, and more. The finely sampled spectral energy distributions of the GOODS-N NIKA2 sources were modeled with state of the art methods, including stellar, dust, synchrotron and AGN-torii components. Among the many derived quantities, I will talk about their dust mass, defining for the first time the evolution of the galaxy dust mass function and dust cosmic density up to redshift z~7.
Finally, I will discuss the dust and gas properties of the intriguing overdensity of star forming galaxies at z~5.2 star forming galaxies identified in GOODS-N.
Detecting point sources in cosmic microwave background maps is essential for characterizing extragalactic populations and addressing foreground contamination. We present the largest catalog of extragalactic sources from the Atacama Cosmology Telescope, spanning 2008-2022 at 95, 150, and 220 GHz. Using improved source detection and classification methods, we distinguish between Active Galactic Nuclei and Dusty Star-Forming Galaxies, substantially increasing the number of detected sources and refining millimeter-wave source counts. Our catalog is a key resource for ALMA and other follow-up studies, offering new insights into galaxy evolution and extragalactic millimeter-wave emission.
In this talk, I introduce a semi-analytic model designed to evaluate the Cosmic Infrared Background (CIB) power spectrum across all frequency and multipole ranges. Our methodology starts from the Halo Model, in order to describe the dark matter distribution in the Universe, capturing its non-linear behavior. We further extend the Halo Model formalism to galaxies, populating dark matter halos with two distinct galaxy populations that exhibit different clustering behaviors and emissivity functions. Via MCMC analyses over Planck and SPIRE data, we constrain the clustering parameters. Our findings indicate discrepancies across different frequency and multipole ranges, either hinting to limitations of the model or suggesting a tension among the experiments.
We analyze measurements of the thermal Sunyaev-Zeldovich (tSZ) effect arising in the circumgalactic medium (CGM) of L galaxies. In our analysis we use the Faerman et al. 2017 and Faerman et al. 2020 CGM models, a new power-law model (PLM), and the TNG100 simulation.
An observation by Bregman et al. 2022 Compton-y profile implies steep electron pressure slopes. Considering the possibility of a hydrostatic equilibrium, we find that the B+22 galaxies favor an isentropic equation of state over an isothermal one. The B+22 results are consistent with a similar work by Das et al. 2022, and with recent (0.5-2 keV) CGM X-ray observations by Zhang et al. 2024 of Milky Way mass systems.
TNG100 underpredicts the tSZ parameters by relatively 0.5 dex for the L galaxies, suggesting that the feedback strengths and CGM gas losses are overestimated in the simulated halos at these mass scales.
Extracting precise cosmology from weak lensing surveys requires modelling the non-linear matter power spectrum, which is suppressed at small scales due to baryonic feedback processes. However, hydrodynamical galaxy formation simulations make widely varying predictions for the amplitude and extent of this effect. Given the recent indications from weak lensing and kinematic Sunyaev-Zel’dovich measurements of a feedback scenario that is more extreme than many hydrodynamical simulations implement, the question remains of whether this scenario is physical and could be reproduced in a simulation that predicts a realistic Universe with respect to observations. I will discuss work exploring a range of empirical AGN feedback models within the FABLE cosmological simulation suite, and highlight an empirical AGN feedback mechanism that is able to produce a greater matter power suppression than fiducial FABLE in agreement with WL+kSZ constraints, whilst maintaining good agreement with all key galaxy, galaxy group, and cluster properties. DESI is delivering kSZ measurements forecasted to have an eight-fold improvement in signal-to-noise and therefore powerful constraining power for baryonic physics. To maximise the return, it is crucial results are validated in a model-independent manner, and therefore that a complementary tool to 'baryonification' exists for WL + kSZ analyses. I will share our development of a hydrodynamical simulation-based emulator for the dependence of the kSZ signal on baryonic feedback processes, and insights from measurements of the kSZ effect in a number of state-of-the-art hydrodynamical simulations. Finally, I will share first constraints on both cosmology and astrophysics from a joint analysis of the DES Y3 cosmic shear and DESI Y1 + ACT kSZ datasets.
Modern multi-platform, multi-band millimeter-wavelength surveys of the sky with arcminute resolution are designed to explore the origin and evolution of the universe. The next generation of CMB experiments, including the Simons Observatory (SO), will address a wide range of pressing scientific questions with unprecedented sensitivity. Among these, one of the primary targets is the faint large-scale B-mode polarization of the CMB, which provides a powerful probe into the high-energy physics of the early Universe. Observing this requires precise control of instrumental systematics, and a clear understanding of how properties such as noise correlations, optical efficiency, and calibration uncertainties propagate from raw data to cosmological parameters. Over the past year, the mid-frequency SO Small Aperture Telescopes (SATs) have undergone extensive on-sky testing, including realistic CMB and calibration scans to assess instrument readiness and data processing. Here we present preliminary polarization maps from the SATs at 90/150 GHz. I will discuss our efforts to characterize the propagation of pre-deployment instrument properties from time-ordered data to maps. Finally, I will highlight upcoming challenges that we expect in our analysis, and our strategies to address them to recover robust cosmological constraints.
MISTRAL is a new facility instrument open to the scientific community that will help investigate the ’missing baryon’ problem, as well as many other scientific cases from extragalactic astrophysics to solar system science. The MIllimeter Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs (MISTRAL) is a cryogenic W-band LEKID camera which has been mounted at the Gregorian focus of the 64-m fully steerable radio telescope Sardinia Radio Telescope (SRT), in Italy, in May 2023. MISTRAL will take advantage of its 12 arcseconds of angular resolution, a 4 arcminutes wide instantaneous field of view and its high sensitivity, which will make this camera one of the most competitive instrument to observe the mm-wave sky. Given that MISTRAL is currently under commissioning, the development of a reliable and efficient map-making and data filtering software is necessary for the analysis of its first acquired data of the sky. I will describe the current status of the commissioning and the first observations, with details on the calibration and the current state of the map-making and data filtering pipeline. This software aims to analyse the data efficiently and quickly, filtering them from instrumental and atmospheric noises and produce a map. The data filtering process employs a customized technique for common mode and a destriping technique in order to mitigate different kinds of systematic effects.
The TolTEC camera is a trichroic polarimeter deployed on the 50-meter Large Millimeter Telescope (LMT) on Sierra Negra in Mexico. It observes in three photometric bands 150, 220, and 280 GHz with respective angular resolutions of 10, 6, and 5 arcseconds. TolTEC achieved first light in 2022 and commenced commissioning in December of that year. Issues with the LMT and TolTEC prevented commissioning observations for most of 2023 and 2024 with TolTEC only observing for a few nights. The TolTEC commissioning campaign resumed in January 2025.
We present an update on TolTEC commissioning with results from after December 2022. This update includes a discussion of techniques used to improve the gain of the TolTEC and LMT optical system, and preliminary images taken a degree-scale region in the Serpens South star cluster and other fields.
OLIMPO is a concept for a balloon-borne instrument to map the thermal and kinematic SZE at high signal-to-noise in a sample of nearby galaxy clusters and connecting bridges. In combination with X-ray data primarily from eROSITA and radio observations from SKA Pathfinders, OLIMPO will provide precise constraints on the turbulent and coherent velocities within the ICM due to structure growth over cosmic time. It will also determine the spatial distribution, thermodynamics, and velocity structure of the filamentary gas in the connecting bridges. I will provide an update on the status of OLIMPO, including recent lab-based measurements demonstrating the maturity of the kinetic inductance detector focal planes and other associated technologies along with scientific projections based on the analysis of existing SZE, X-ray, and radio data and mock OLIMPO observations.
The Next-generation Extended Wavelength-MUltiband Sub/millimeter Inductance Camera (NEW-MUSIC) on the Leighton Chajnantor Telescope (LCT) will be a first-of-its-kind, six-band, trans-mil-li-me-ter-wave (``trans-mm'') polarimeter covering 2.4 octaves of spectral bandwidth to open a new window on the trans-mm time-domain frontier, in particular new frontiers in energy, density, time, and magnetic field. NEW-MUSIC's broad spectral coverage will also enable the use of the Sunyaev-Zeldovich effects to study accretion, feedback, and dust content in the hot gaseous haloes of galaxies and galaxy clusters. Six-band spectral energy distributions, with polarization information, will yield new insights into stellar and planetary nurseries. NEW-MUSIC will employ hierarchical, phased arrays of polar-i-za-tion-sensitive superconducting slot-dipole antennas, coupled to photolithographic bandpass filters, to nearly optimally populate LCT's 14' field-of-view with six spectral bands over 80-420 GHz (1:5.25 spectral dynamic range; 2.4 octaves). Light will be routed to AlMn microstripline-coupled, parallel-plate capacitor, lumped-element kinetic inductance detectors (MS-PPC-LEKIDs), an entirely new KID architecture that substantially enhances design flexibility while providing background-limited performance. Innovative, wide-bandwidth, etched silicon structures will be used to antireflection-treat the back-illuminated focal plane. NEW-MUSIC will cost-effectively reuse much of the MUSIC instrument, initially deploying a quarter-scale focal plane capable of the bulk of NEW-MUSIC science followed later by a full-FoV focal plane needed for NEW-MUSIC wide-area survey science.
With the advent of current and future high-resolution CMB experiments, the kinematic Sunyaev-Zel'dovich (kSZ) effect has become a unique observational probe of the distribution of baryons and velocities in the Universe. In this work, we propose a novel binned bispectrum of the form temperature-temperature-density to extract the late-time kSZ effect from cleaned CMB maps. Unlike 'kSZ tomography' methods, this estimator can use any tracer of the large-scale structure density field projected along the line-of-sight and does not require individual redshifts. With our method, we forecast signal-to-noise ratios (SNR) of ∼100-200 for the upcoming Simons Observatory (SO) and CMB-S4 correlated with a galaxy sample from WISE that is restricted to the linear regime. We also extend galaxy modes into the non-linear regime and explore this harmonic space to show that the SNR peaks for squeezed triangles that have a short (linear) density mode and long temperature modes in harmonic space. The existing kSZ2-density projected-fields estimator compresses the rich information contained in this bispectrum across various scales and triangle shapes. Moreover, we find that the lensing correction to our estimator's signal is relatively small. We study the dependence of this kSZ signal on ΛCDM parameters for SO and CMB-S4 and forecast initial constraints on the sum of neutrino masses while restricting to the linear galaxy bias regime. Our work illustrates the potential of the projected-fields kSZ bispectrum as a novel probe of baryonic abundance and beyond-ΛCDM cosmology with upcoming precision measurements.
I will present our upcoming kSZ velocity reconstruction analysis with ACT and DESI-LS, using a novel optimal quadratic power spectrum estimator. I will also discuss foregrounds for this analysis, as well as a method to potentially improve the SNR using machine learning of the galaxy to electron density map.
One exciting application of forthcoming CMB surveys is the measurement of CMB secondary anisotropies, including the kinetic Sunyaev Zel'dovich (kSZ) effect. By combining measurement of the kSZ effect in the CMB with galaxy survey data, one can reconstruct the large-scale radial velocity field, which contains a wealth of cosmological information. This technique, known as kSZ tomography, has been demonstrated to have excellent detection prospects and a diverse range of applications. In this talk, I will discuss how forthcoming surveys will enable two such applications of kSZ tomography, in particular for probing fundamental physics in both the early and late Universe. First, I will demonstrate how kSZ tomography can tell us about light particles in the primordial Universe by searching for distinct signatures of non-Gaussianity lurking in large scale galaxy bias. I will emphasize some scenarios that give rise to such signatures, and show that the sensitivity is strong enough to outperform some CMB searches. Second, I will discuss the possibility of using kSZ tomography to probe the sum of the neutrino masses. Focusing on kSZ tomography as an independent probe of the growth of large scale structure, I will emphasize how this use-case hinges on some astrophysical uncertainties, which future measurements may circumvent.
In this talk, I will summarize the latest results from ongoing kSZ tomography velocity-reconstruction programs centered at the Perimeter Institute. Highlights will include the most recent LSS × CMB data analyses, featuring the most stringent constraints to date on primordial non-Gaussianity from scale-dependent galaxy bias in galaxy-velocity correlations. I will also introduce a new analysis pipeline and publicly available code for velocity reconstruction, simulations, and data analysis. Additionally, I will present a novel approach to simulating galaxy data that is both more practical and simpler than traditional mocks. This method not only enables an exact determination of the window function but also provides a sufficiently accurate estimate of the covariance, making it a robust and efficient alternative.
Baryonic matter only accounts for 5% of the mass-energy density of our Universe, where the other 95% is shared between dark energy and dark matter. About half of these baryons are currently undetected, and this discrepancy between predicted and observed baryons is known as the “missing baryon” problem. Cosmological simulations predict that a significant fraction of the missing baryons could reside in the form of the warm–hot intergalactic medium (WHIM) trapped inside large scale structures that constitute the cosmic web. Thus, the characterization of the WHIM is a crucial piece of the missing baryon puzzle. Since the baryons reside in a low density, low temperature state, they are difficult to observe.
A useful tool to probe the missing baryons is the Sunyaev-Zel’dovich effect (SZe), an anisotropic spectral distortion of the cosmic microwave background (CMB), caused by the inverse Compton scattering between the hot electrons in galaxy clusters or filaments and the low energy photons of the CMB. This effect has been extensively used by Planck to study clusters and few filament candidates, but at a low resolution of ~10 arcminutes. More recent ground-based CMB experiments like Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) have enabled the study of galaxy clusters at arcminute scales. However, only few observations of individual cosmic filaments exist because of their extremely faint SZe footprint. These single detections are limited to multiple cluster systems, in which the filament is compressed and heated as the clusters gravitate into each other, increasing the signal.
In this contribution we present results on the detection of hot gas outside galaxy clusters obtained with the latest high resolution (1.65´), high sensitivity Compton-y maps from ACT. We consider a set of candidate double cluster systems extracted from a preliminary ACT-DR6 catalog of blindly detected clusters to study their general properties through stacking. This sample in focuses on short filaments with a projected length Lfil< 10 Mpc and typical halo mass M500 ~ 2e14 m_sun. Additionally, we study individual pairs of clusters to identify promising candidates for follow-up observations using high resolution millimeter cameras or X-ray satellites.
Primary anisotropies and gravitational lensing of the cosmic microwave background (CMB) provide a wealth of information on cosmology. In an analysis that extracts such information, a first step is to create sky maps of anisotropies in the I, Q, and U Stokes parameters of millimeter-wave radiation fields. We will present the procedure that we used to make and validate new sky maps of the anisotropies in the frequency bands centered at 95, 150, and 220 GHz from data taken with the third-generation camera on the South Pole Telescope (SPT-3G) during the first two years (2019 and 2020) of the SPT-3G Main survey. We will discuss the method that we used to convert time series of individual detectors to sky map pixels, the calibration and cleaning steps that we applied to the maps to reduce known biases, and a suite of tests that we conducted to search for potential systematic errors. Although we detected systematic errors, they were expected to have negligible effects on scientific results obtained from the maps. These maps were used for new and significantly improved SPT-3G measurements of temperature and E-mode polarization anisotropies and gravitational lensing of the CMB.
I will present the cosmological analysis from the simultaneous Bayesian estimates of gravitational-lensing potential bandpowers and unlensed cosmic microwave background (CMB) EE bandpowers using the polarization maps from the South Pole Telescope (SPT) observed in 2019/20. These observations produce the deepest high-angular-resolution CMB polarization maps at 90, 150, and 220 GHz to date, making the standard Quadratic Estimation (QE) method suboptimal for lensing reconstruction. The Marginal Unbiased Score Expansion (MUSE) method enables an optimal map-level Bayesian inference of lensing potential bandpowers and unlensed CMB EE bandpowers, effectively using all N-point statistics of the CMB polarization maps. The resulting EE spectrum at l>2000 and lensing spectrum at L>350 are the most precise to date. The constraints on the Hubble constant (H0) and the amplitude of structure growth (S8) from this work are comparable to those from Planck using full-sky temperature and polarization observations, enabling a powerful test of the LCDM model. With the lensing potential bandpowers reconstructed from the CMB polarization signal, we test the anomaly of excess lensing power from the LCDM prediction, and detect the impact of non-linear structure evolution on CMB lensing. We also explore the extensions of the LCDM models.
SPT-3G, the third-generation camera on the South Pole Telescope (SPT-3G), is being used to observe the cosmic microwave background (CMB) anisotropies to unprecedented depth at arcminute resolution. The temperature and E-mode polarization anisotropies of the CMB provide a wealth of information on the composition and evolution of the universe. This talk presents the upgraded cosmological analysis of the TT, TE and EE power spectra based on data collected in 2019-2020 and associated maps. LCDM parameter constraints will be comparable to Planck’s, while remaining mostly independent from the satellite experiment, thus allowing to test the consistency of the data sets and probe evidence of physics beyond the standard model. Combined with 2019-2020 SPT-3G CMB lensing reconstruction and other experiments, these results will produce some of the tightest constraints on cosmological parameters to date.
I will present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, as measured from the Atacama Cosmology Telescope (ACT) Data Release 6 maps. These maps cover 19,000 square degrees in bands centered at 98, 150, and 220 GHz, with white noise levels three times lower than Planck in polarization, and angular resolution roughly five times higher. I will describe the model developed to fit these data, including detailed treatment of mm-wave foregrounds, and extensive robustness tests of the full analysis pipeline. I will then present constraints on cosmological parameters derived from the ACT DR6 power spectra, as well as from a combination of ACT and legacy data from Planck. ACT and Planck CMB lensing data and baryon acoustic oscillation data from DESI are also used to break geometric degeneracies. Using these data, I will describe the results of several searches for new physics and tests of foundational assumptions of the cosmological model.
Cosmic birefringence is a hypothetical signature of parity violation in the electromagnetic interaction, and would manifest as a rotation of CMB polarisation as the signal travels through our Universe. This effect is degenerate with instrument polarisation, making it a calibration and data analysis challenge to constrain. In this talk, I will focus on the sensitivity to cosmic birefringence of BICEP3, a CMB telescope located at the South Pole and observing at 95GHz. I will discuss the relative contributions of instrumental noise, astrophysical signals, and systematics, yielding a sensitivity to the birefringence angle of σ(α)=0.078° for 2 years of observations. I will also compare how these contributions are projected to evolve as we expand the dataset from the published 2 years (2017-2018) to 8 years of observations (2017-2024). Finally, I will provide some perspective on how future experiments will expand birefringence searches, with expected improvements such as delensing, multi-frequency observations, and increased CMB polarisation sensitivity.
Reference: BICEP/Keck XVIII: Measurement of BICEP3 polarization angles and consequences for constraining cosmic birefringence and inflation, The BICEP/Keck Collaboration, 2024 (accepted for publication in PRD)
Galaxy clusters are the largest gravitationally bound objects in our Universe, are dark-matter dominated, and have the baryonic mass component mainly composed by X-ray emitting plasma also observable through Sunayev-Zeldovich effect at millimeter wavelengths. Thus, X-ray (and SZ) data provide a unique view of their structure.
Using data and results from our ongoing Heritage XMM-Newton program CHEX-MATE, I will revise the current observational constraints on the fundamental properties defining the cluster's structure, how these constraints align with the prevailing cosmological paradigm, what are the outstanding issues, and what are our strategies to address them with further to construct a consistent picture of how galaxy clusters form and evolve.
The NIKA2 camera operating at the IRAM 30-m telescope has unique performance for the resolved observation of the Sunyaev-Zel’dovich effect towards galaxy clusters. As part of the NIKA2 guaranteed-time, the SZ Large Program (LPSZ) is devoted to the high-angular resolution SZ mapping of a representative sample of SZ-selected clusters, at intermediate to high redshift, drawn from the catalogues of the Planck satellite and of the Atacama Cosmology Telescope. Central to this program is the synergy between SZ observations and X-ray data, utilizing measurements from XMM-Newton or Chandra. The main goal of this program is to provide the community with unprecedented measurements of the universal pressure profile and of the scaling law linking the SZ observable to the hydrostatic mass. This effort extends prior studies to encompass higher redshifts and lower mass ranges, aiming to improve the accuracy of cluster cosmology.
I will review the final results concerning: the sample of clusters, the science-ready products (maps, thermodynamic profiles, and integrated quantities), the universal pressure profile and the mass-SZ scaling relation. Cosmological implications of the last two will be presented alongside studies focusing on cluster physics.
We present the latest development of "Baryon Pasting", a novel framework that adopts a physics-based approach for forward-modeling SZ and X-ray observations of galaxy clusters and groups. Baryon Pasting enables efficient exploration of the vast astrophysical and cosmological parameter space required for current and upcoming millimeter-wave surveys, such as the Simons Observatory and CMB-S4, while maintaining the physical accuracy of modern hydrodynamical simulations. This makes Baryon Pasting particularly powerful for disentangling the impact of cluster and group astrophysics from cosmology. Using the half-sky Baryon Pasted Uchuu lightcone simulation, we demonstrate significant map-level systematic effects that were previously difficult to quantify. Application of the Baryon Pasting model to the eRASS1 X-ray power spectrum has also yielded precise cosmological and astrophysical constraints, shedding new light on the ongoing $S_8$ tension. Looking forward, we discuss how integrating Baryon Pasting with state-of-the-art cosmological simulations and cutting-edge machine learning techniques will fully unlock the potential of next-generation multiwavelength Stage IV surveys through efficient and interpretable modeling of the observable universe.
Post-processing techniques emulating baryonic physics in gravity-only simulations are a cornerstone of modern cosmology. In particular, predicting the thermodynamic properties of the intracluster gas is necessary to exploit these simulations for galaxy cluster cosmology in the millimeter-wave and X-ray domains. In this talk, I will introduce picasso, a model to predict thermodynamic properties of the intracluster medium from halos in gravity-only simulations. Predictions are based on the combination of an analytical gas model, mapping gas properties to the gravitational potential, and of a machine learning model to predict the model parameters for individual halos based on their scalar properties, such as mass and concentration. The model is trained using pairs of gravity-only and hydrodynamic simulations with identical initial conditions. I will show that picasso can make remarkably accurate and precise predictions of intracluster gas thermodynamics. I will discuss the numerical implementation of the picasso model, which is publicly available as a Python package that includes trained models and can be used to make predictions easily and efficiently in a fully auto-differentiable and hardware-accelerated framework. I will finish by presenting the first synthetic data products created by using picasso to emulate intracluster gas thermodynamics in state-of-the-art gravity-only cosmological simulations.
In Sunyaev-Zeldovich (SZ) cluster cosmology, accurately determining cluster masses is crucial for constraining cosmological parameters through cluster number counts.
As the mass is not an observable, a scaling relation is needed to link cluster masses to the integrated Compton parameter Y, i.e., the SZ observable, to exploit data from large millimeter surveys. Current cosmological results use a scaling relation obtained with clusters at low redshift (z < 0.5) observed in X-ray and in SZ at an angular resolution above 1 arcminute.
The SZ large program (LPSZ) of the NIKA2 collaboration is a sample of clusters at intermediate to high redshift (from z = 0.5 to z = 0.9) observed at similarly high-angular resolution both in SZ and in X-ray. From these data, it will be possible to study various systematic effects that can affect the scaling relation.
In this talk, I will present the final result for the SZ-Mass scaling relation of the LPSZ as well as its impact on cluster cosmology.
Understanding the scaling relations between galaxy cluster properties (such as mass, luminosity, richness, and luminosity) is crucial for unraveling the physical processes shaping them. However, these relations are highly sensitive to uncertainties in sample selection functions, requiring assumptions about the abundance and properties of unobserved populations. The potential impact of selection effects is substantial, as clusters selected via different methods appear to follow distinct scaling relations.
In this talk, I present the Compton Y vs. mass scaling relation derived from a statistical sample of galaxy clusters selected solely by gravity (shear), contrasting it with the scaling relations obtained from ICM-selected cluster samples. Even after accounting for selection effects and a mass bias that we found to be (1-b) = 0.72+-0.09,, analyses based on ICM-selected samples show significant discrepancies: an excessively large intercept, unusually low scatter, and a conspicuous absence of clusters that are exceptionally faint in Compton Y for their mass.
Finally, I outline potential paths forward for observing larger cluster samples with SZ facilities, leveraging ongoing surveys such as Euclid and LSST.
We present our analysis of the factors that impact the reconstruction of density profiles in galaxy clusters, which are a fundamental tool for studying the properties of the intra-cluster medium and a key ingredient for measuring the total mass radial profiles under the assumption of hydrostatic equilibrium.
We used a sample of 105 galaxy clusters drawn from cosmological simulations mirroring the CHEX-MATE representative sample of 118 clusters selected via the SZ effect. Each simulated cluster's X-ray emission was projected along 40 lines of sight. We leveraged this unique dataset to discriminate and quantify, for the first time, the impact of factors such as intrinsic dynamical state.
We derived density profiles using both the azimuthal mean and median methods and found that, on average, both provide a robust retrieval of the true gas density. However, density reconstruction becomes less reliable as a cluster becomes more morphologically or dynamically disturbed.
We also investigate whether the mean-to-median density method can be used to probe clumpiness. While we find no correlation with cluster dynamical state, there is a clear radial trend, suggesting that this method is not reliable on an individual cluster basis. Finally, these results have been used to interpret the statistical properties of the CHEX-MATE density profiles.
Galaxy clusters form through the accretion of smaller structures, with mergers of subclumps and the sloshing of cold gas in higher-entropy environments affecting their intracluster medium (ICM) distribution. These processes leave observable imprints, such as edges, shocks, cold fronts, and discontinuities in surface brightness, as well as variations in integrated quantities.
In this study, we systematically investigate the occurrence, distribution, and properties of surface brightness discontinuities in the X-ray maps of the CHEX-MATE objects, a large, minimally biased, signal-to-noise-limited sample of 118 galaxy clusters detected by Planck through the Sunyaev–Zeldovich effect. These clusters have been observed in X-ray with XMM-Newton through dedicated 3 Msec exposures within the Heritage program, and are designed to become the reference for clusters in the local volume and in the high-mass regime. We objectively identify discontinuities, minimizing biases from prior assumptions about merger geometry or the presence of features in other wavelengths (e.g., radio relics). To achieve this, we focus on regions where local deviations from a smooth surface brightness distribution occur.
This work provides the first comprehensive characterization of the frequency, location, extent, and halo dependence of these features in a large and representative sample of galaxy clusters, offering new insights into the physical mechanisms shaping the ICM.
In this talk, I will introduce the Resolved Cluster Evolution Sunyaev-Zeldovich Survey (ReCESS): a 200-hour-plus observing campaign aimed at resolving the intracluster medium (ICM) through the thermal Sunyaev-Zeldovich (tSZ) effect in 25 ACT-selected galaxy clusters within a redshift range of $1.2 < z < 2$ using MUSTANG-2 on the GBT and ALMA. I will present the first results on the average tSZ-derived pressure distribution of the ICM at $z > 1.2$, mapped from the core (inner $\approx80$ kpc) to the virial radius, by combining high-resolution data with ACT observations. Whenever available, we incorporate X-ray observations into our forward modeling routine to obtain a full thermodynamic picture of the ICM. I will illustrate this method through a case study of a cluster at $z = 1.7$, for which excellent XMM-Newton, Chandra, and ALMA data are available. Finally, ReCESS enables the search for and study of shocks, mergers, and feedback mechanisms at an epoch when the ICM is still forming. While not all observations have been completed, we have identified several extremely interesting clusters with unique ICM morphologies, including the detection of a “tSZ cavity” at $z = 1.3$—only the second tSZ cavity ever detected.
The Atacama Cosmology Telescope (ACT) was a ground-based CMB experiment in the Atacama desert in Chile that observed the millimeter sky between 2008 and 2022 at frequencies ranging from 90 GHz to 220 GHz with three detector arrays. The combination of the ~arcminute angular resolution, large footprint, and high cadence of the experiment made the instrument an excellent tool for millimeter time-domain science. We now have an initial catalog of ACT light curves containing the ~200 brightest active galactic nuclei (AGN) in its data, sampled over several years. In this talk we will describe how we are using these light curves for multiwavelength cross-correlation with optical and gamma-ray light curves. Cross-correlating emission in these different bands can aid in understanding which of the leptonic or hadronic processes is most often responsible for emission in the two components of the blazar SED, and the relative locations of the emission regions for different wavebands.
Wide-area cosmic microwave background (CMB) surveys, while optimised for precision cosmology, also contain many thousands of active galactic nuclei (AGN) observed at regular cadences. The majority of these AGN are blazars with highly variable fluxes due to relativistic shocks and motions in their jets. Observing them in millimetre wavelengths (mm) with CMB telescopes fills in a portion of the electromagnetic spectrum that is traditionally understudied, probing deeper into the jets than longer-wavelength radio data. Recently, robust sinusoidal variations in radio and millimetre light curves have provided strong evidence for supermassive black hole binaries (SMBHB) in a subpopulation of AGN. I will present AGN light curves from observations by the Atacama Cosmology Telescopes (ACT) and describe lessons learnt from the data reduction. I will also outline their general properties and some of the exciting science they enable, particularly SMBHB studies. Finally, I will describe how further work on existing ACT data and future data from the Simons Observatory (SO), will produce a library of AGN mm light curves of unprecedented size and utility.
Recent cosmic microwave background (CMB) experiments have opened the millimeter-wave (mm) regime of the electromagnetic spectrum to time-domain astrophysics. While mm observations have been conducted in the past, this is the first time that transient events have been blindly discovered in non-targeted surveys, as opposed to follow-up or pointed observations. Past mm-wave transient surveys with the South Pole Telescope (SPT) targeted the extragalactic sky and have detected hundreds of transient events, with most of them being galactic flaring stars. In this talk, we will present the first mm-wave time-domain survey towards the Galactic plane with SPT-3G (the third generation SPT camera). This survey consists of approximately 500 observations covering 100 square degrees of the Galactic plane in both 2023 and 2024, with plans for more observations in the coming years. The survey measures intensity and linear polarization in three bands centered at 95, 150 and 220 GHz. Until now, we have detected two transient events above a threshold of 5𝜎 in both 95 and 150GHz bands. Both events are associated with previous known binary systems with white dwarf accretors. Future analysis will involve lowering the detection threshold and improving the transient pipeline to be sensitive to timescales of minutes.
The 6m Atacama Cosmology Telescope (ACT) has been a powerful tool for studying the cosmic microwave background (CMB) and sources and transients away from the galaxy. However, its high sensitivity and wide-field imaging capabilities also make it an excellent instrument for detecting transient phenomena near the Galactic plane, where traditional surveys face challenges due to high stellar density and foreground emission such as dust and synchrotron. In this study, we leverage ACT's millimeter-wave observations to search for transient events, such as stellar flares, supernovae, and other Galactic transients, in regions close to the Milky Way.
We present a systematic analysis of ACT data, focusing on time-variable signals in the 90 GHz, 150 GHz, and 230 GHz bands. By applying source detection algorithms on single-scan maps, we identify and characterize transient candidates while mitigating contamination from instrumental noise and astrophysical foregrounds. Our preliminary results reveal several promising transient events, including potential stellar flares and previously unknown sources. We discuss the implications of these findings for understanding the population of Galactic transients and the potential of millimeter-wave surveys for time-domain astronomy.
This work demonstrates the untapped potential of CMB experiments like ACT for transient discovery and highlights the importance of multi-wavelength follow-up observations to confirm and classify detected events. Future efforts will expand this search to the full ACT dataset and explore synergies with other time-domain surveys, paving the way for a deeper understanding of transient phenomena in the Galactic plane.
The next decade will be transformative for time-domain and transient astronomy, with a new generation of wide-field surveys poised to uncover a vast population of time-varying and transient astrophysical phenomena. The Simons Observatory (SO), a new cosmic microwave background (CMB) experiment, will provide high-cadence millimeter-wave observations over ~half the sky, notably delivering transient alerts and bright source light curves to the public in near real-time. In this talk I will discuss the unprecedented, publicly available dataset of millimeter light curves and the projected scientific output of both astrophysical transients and known bright objects. The 10 year (Advanced) SO timeline is also synergistic with optical surveys like the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), radio surveys such as the Square Kilometer Array (SKA) and the Deep Synoptic Array (DSA-2000), and X-ray surveyors such as Einstein Probe (EP), among many others. SO will provide invaluable and open access to millimeter time-domain data, marking a fundamental change in the way CMB surveys interact with the broader astrophysical community.
Invited talk on LIM
The Shirokoff Line-Intensity Mapper (SPT-SLIM) is a mm-wavelength, superconducting on-chip spectrometer observing redshifted CO in the 2mm atmospheric window using the 10-meter South Pole Telescope (SPT). The instrument was recently deployed for the first time during the 2024-2025 austral summer season at South Pole, where it conducted a short two-week observing campaign. We will present an overview of the SPT-SLIM instrument and project, discuss early results from its initial deployment, and preview the prospects for a longer survey using upgraded instrumentation in the 2025-2026 austral summer.
Line Intensity Mapping, LIM, is an emerging observational technique that measures the integrated emission from galaxies as fluctuations in a 3D cosmic volume. By doing so, it aims to fill a key gap in studies of cosmology and galaxy formation – LIM data cubes are sensitive to the emission from all galaxies in a population, even the very faintest. LIM experiments can thus study the evolution of galaxy tracers (for example, molecular gas) throughout cosmic time without being limited to the brightest objects and in a way that scales efficiently to very large cosmic volumes. In this talk, I will discuss COMAP (the CO Mapping Array Project), a LIM experiment targeting dense molecular gas in galaxies via their CO$(1-0)$ emission at redshifts spanning from the peak of cosmic star formation to the Epoch of Reionization. I will discuss COMAP’s field-leading constraints on the CO power spectrum at $z\sim 3$, and the range of analysis techniques currently being used to further constrain high-redshift CO.
I will talk about reconstructing the non-linear matter power spectrum $P(k)$ using a joint analysis of gravitational lensing of the cosmic microwave background (CMB) and lensing of galaxies. This reconstruction is motivated by the $S_8$ tension between early-universe CMB predictions and late-time observables. We use CMB lensing data from the Atacama Cosmology Telescope DR6 and cosmic shear data from the Dark Energy Survey (DES) Y3 release to perform a gravity-only (i.e. no baryonic feedback) fit to $P(k)$ in bins of wave-number, within $\rm{\Lambda CDM}$. We find that with DES cosmic shear data alone, $P(k)$ departs from the early-universe CMB prediction on all scales. The joint fit with CMB lensing is consistent on large scales $k<0.2 \;{\rm Mpc}^{-1}$ but shows a $\sim 2 \sigma$ deviation from scale-independence when extending to $k = 10 \;h/\mathrm{Mpc}$. We compare our agnostic $P(k)$ reconstruction to baryonic feedback models and non-standard dark matter models: reasonable variations of both scenarios can recover the shape and amplitude of the suppression. We discuss the advances needed to disentangle these physical effects with a full mapping of $P(k,z)$.
Precision measurements of the cosmic microwave background’s gravitational lensing provide a uniquely powerful window into the distribution of dark matter, offering insights into neutrinos, dark energy, and enabling powerful consistency tests of the standard cosmological model.
In this talk, I will describe ongoing efforts in producing state-of-the-art CMB lensing maps from the final release of the Atacama Cosmology Telescope. By combining improved nighttime data, daytime observations, and large-scale CMB observations from Planck, these maps will deliver state-of-the-art high-fidelity lensing reconstructions over 30% of the sky. I will highlight the preliminary constraints on cosmic structure growth, neutrino mass limits and other key cosmological parameters that these maps will enable. I will also explore the transformative potential of the Simons Observatory in propelling CMB lensing science to the sub-percent precision regime, discussing the ongoing transition to SO and the potential and the technical challenges that lie ahead in next-generation mass mapping.
The weak gravitational lensing of the cosmic microwave background photons due to the line-of-sight matter distribution is a powerfully precise probe of cosmology. One of the key insights that this phenomenon known as CMB lensing unveils is an unbiased mapping of dark matter and its characteristics, allowing us to trace the formation and growth of large-scale structure over vast cosmic epochs. In this talk, I will demonstrate how I’ve used CMB lensing maps from the Atacama Cosmology Telescope (ACT) and the Planck satellite with two different approaches to constrain structure growth. After briefly discussing my past work cross-correlating ACT Data Release 6 (DR6) + Planck CMB lensing with the spectroscopic luminous red galaxies from the Dark Energy Spectroscopic Instrument (DESI), I will present ongoing efforts in measuring one of the highest significance detections of the CMB lensing power spectrum using the final data release of ACT. I will highlight improvements from the DR6 analysis, such as the novel usage of daytime observations and improved techniques to process CMB data jointly with Planck, and showcase preliminary constraints on the structure growth parameter $S_8^{\rm CMBL}$. Finally, I will interpret these state-of-the-art CMB lensing constraints in context to the “S8 tension” between early-time predictions of structure growth and late-time observables, as well as mentioning the outlook for future CMB lensing analyses.
I will introduce two new methods for large-scale structure (LSS) studies in mm-wave astronomy: (1) redshift tomography and (2) map-level density reconstruction, and demonstrate them with data to probe the thermal SZ history, cosmic infrared background (CIB), and Milky Way dust.
For the first method, I will focus on a new CIB tomography result in Chiang+2025, where we deproject 11 sky intensity maps from Planck, Herschel, and IRAS by cross-correlating diffuse photons in each band with galaxies and quasars from SDSS/BOSS/eBOSS in a tomographic manner. By combining hundreds of redshift- and frequency-dependent two-point function amplitudes, we achieve a 60-sigma detection of the evolving CIB spectrum over 0 < z < 4. This establishes a CIB benchmark for future CMB experiments and provides a complete census of cosmic dust and star formation history. Additionally, we detect the SZ background and, for the first time, cosmic CO and [CII] lines on top of the CIB continuum without line confusion.
For the second method, we reconstruct the LSS (CIB+SZ) field in mm-wave data at the map level, with the Fourier phases of the cosmic web fully constrained by 600 million WISE galaxies—the largest existing galaxy catalog. I will present the first example at 100 microns from Chiang 2023, where we strip the CIB from the SFD Milky Way dust map. I will also discuss the extension to 3D reconstruction and an ongoing project to apply the method to all Planck HFI bands, delivering a full-sky legacy component separation product for the CMB community.
Line intensity mapping (LIM) is an emerging technique in observational cosmology to spatially and spectrally map the aggregate line emission from large-scale structures, which promises to offer invaluable insights into physical processes that govern galaxy formation and evolution in the cosmological context. The mm-wave sky has been and will be surveyed by a number of LIM experiments such as CONCERTO, TIME, SPT-SLIM, FYST/CCAT-prime, and TIFUUN to study early galaxy formation and cosmic reionization. Novel simulation and analysis tools are thus required to harness the full power of these LIM observations. I will discuss the development and applications of LIMFAST, a semi-numerical tool that builds on the 21cmFAST code for simulating a multitude of high-redshift LIM signals, including popular target lines like [CII] and [OIII] for mm-wave LIM experiments. I will first introduce how state-of-the-art models of galaxy formation in the early Universe are implemented in LIMFAST to realistically simulate the LIM signals. I will then present recent developments of a simulated-based inference framework that employs neural density estimation to learn key physical aspects of early galaxy formation, such as the star formation law and stellar feedback, from LIMFAST simulations of [CII] and [OIII] signals.
Line intensity mapping (LIM) of molecular lines such as CO and [CII] is emerging as a powerful technique for probing cosmic structure and astrophysical processes, spanning multiple wavelengths but particularly impactful in the mm regime. These tracers provide key insights into galaxy formation, the interstellar medium, and cosmic star formation across a wide range of redshifts, complementing other mm-wave observations such as the thermal and kinetic SZ effects. In this talk, I will present SLICK-LIM, a new model for LIM predictions built using SLICK (the Scalable Line Intensity Computation Kit, https://iopscience.iop.org/article/10.3847/1538-4357/ad642c), which leverages hydrodynamic simulations and machine learning to generate realistic light cones for CO, [CI], and [CII] emission. Applying this framework to the SIMBA, IllustrisTNG, and CAMELS simulations, I will showcase predictions for upcoming LIM experiments, featuring physically-driven luminosity calculations and their implications for multi-wavelength studies. Finally, I will discuss ongoing applications of SLICK to diverse astrophysical problems, from dark CO studies and luminosity profiles to the role of AGN in modifying observed molecular line emission.
There is no consensus on how baryonic feedback shapes the non-linear matter power spectrum from hydrodynamical simulations. With improvements in survey size and methodology, this uncertainty is now a limiting systematic for cosmic shear inference at small scales. Modern simulations are tuned to reproduce a variety of galaxy observations, however, they still predict a wide range of feedback magnitudes, and constraints from weak lensing + kinematic Sunyaev-Zel’dovich (kSZ) effect favor an even stronger feedback scenario, and lower gas fractions. In this talk, we address uncertainties in the observational landscape with a multi-observation view of the same sample of galaxies. I present measurements for a the gas distribution, as seen by X-ray, kSZ and galaxy-galaxy lensing for the same sample of galaxies in bins of mass and redshift, in comparison to predictions from the FLAMINGO simulations.
The hot circumgalactic medium (CGM) is believed to host most of the baryons and metals that are missing from the stellar disk and ISM. However, detecting the hot CGM is extremely challenging due to its faintness and the complexity of the background in mm and X-ray. We have cross-correlated the WISExSuperCosMos galaxy catalog with the Compton-y map derived from the CMB data of the Atacama Cosmology TelescopexPlanck to estimate the thermal pressure of the CGM of 0.63 million L* spiral galaxies. The thermal energy of the CGM of these galaxies evolves more strongly with mass than the self-similar relation of purely gravity-driven halos. We have also found a non-monotonic trend of baryon fraction as a function of mass, with a certain mass range being baryon sufficient. We complement the tSZ stacking analyses with deep X-ray observations of individual galaxies. By carefully selecting an optimum target, devising a novel method, and performing two independent analyses of our Suzaku and XMM-Newton data, we have detected the emission from the hot CGM of a star-forming spiral galaxy at 4sigma significance. The mass of the detected hot CGM is sufficient to account for the missing galactic baryons. Our results provide insights into the impact of galactic feedback on the hot CGM and set a benchmark for designing experiments with next-generation mm and X-ray facilities.
For decades, instruments operating in the X-ray and mm wavebands have provided the capability of observing the hot intracluster medium (ICM) of galaxy clusters, and determining its density, temperature, and pressure. It has been possible only in recent years to determine the spatially resolved kinematic properties of the cluster gas via measurements of line shifting and broadening in the X-ray and the kinetic Sunyaev-Zeldovich effect in the mm. Such measurements are essential for probing the properties of turbulence and bulk motions driven by mergers and feedback from active galactic nuclei, helping to fill major gaps in our understanding of ICM physics. I will present recent simulation comparisons to these state-of-the art kinematic observations, and show how they can be used to infer ICM properties and what challenges remain.
The ALMA Wideband Sensitivity Upgrade (WSU) is an ongoing partnership-wide initiative that will dramatically increase the ALMA system’s observing efficiency across ALMA’s entire wavelength range and for all observing modes. As part of the WSU, most of the observatory’s hardware elements will be replaced or upgraded, including key receivers and signal chain components; a new correlator, the Advanced Technology ALMA Correlator -ATAC) will be installed.
This comprehensive system rehaul will result in a transformational increase of the instantaneously correlated bandwidth, up to at least 16 GHz per polarization for all receivers, combined with significantly improved receiver and digital path efficiency. The entire instantaneously correlated bandwidth will be accessible at any spectral resolution, so that observers will not need to trade bandwidth for spectral resolution, significantly increasing the efficiency of spectral scans for redshift and chemical surveys. The large gain in continuum mapping speed (increased by a minimum factor of 3) directly translates in improved ability to efficiently detect and map fainter and farther sources, from asteroids to forming planets and dusty galaxies at high redshifts.
In this talk I will present the scope of the WSU, the status of the project and its impact on a variety of scientific cases.
The CCAT Observatory's Fred Young Submillimeter Telescope, a novel, high-throughput, 6-meter aperture telescope, is currently under construction at 5600 m on Cerro Chajnantor in the Chilean Atacama Desert. CCAT will address a suite of science goals, including Big Bang cosmology, star formation, line-intensity mapping of cosmic reionization, galactic magnetic fields, astronomical transients, galaxy evolution over cosmic time, and more. We highlight the complementarity of CCAT and current mm-wave surveys and describe CCAT's submillimeter measurement capabilities with its first generation science receiver: Prime-Cam. Prime-Cam will be capable of fielding over 100,000 kinetic inductance detectors to enable over 10x faster mapping speed than previous submillimeter observatories in windows from 0.3 – 1.1 mm (280 – 850 GHz). We present CCAT's astrophysics and cosmology science goals with Prime-Cam, the project status, and plans for early science observations starting in 2026.
CMB-S4, the next-generation ground-based cosmic microwave background (CMB) experiment, will make measurements with unprecedented precision and provide fundamental new insights into physics and astronomy. Its key measurements will include the search for primordial gravitational waves, probes of the nature of dark matter and dark energy, mapping matter throughout the Universe, and the detection of transient events in the microwave sky. In this talk, I provide an overview of the CMB-S4 science program, highlighting the rich astrophysical measurements it will enable. I will also describe the instrument configuration and project status.
AtLAST is a next-generation concept for a 50-m single dish telescope covering 30-950 GHz in frequency and featuring a field of view >500 times larger than that of current large mm-wave facilities like the Large Millimeter Telescope. When it is built, it will be the first submm single dish with >20-m aperture ever and the only >12-m single dish with full access to the southern sky. AtLAST will also house the largest receiver cabin ever, with space to accommodate up to 6 massive instruments (the 4 smaller of which can be as large as Prime Cam or the large aperture telescope receivers of SO and CMB-S4, and the 2 Nasmyth-mounted instruments each being up to 4-5x larger). The first design study for AtLAST finished in August 2024, resulting in 8 refereed science cases, identification of 3 key science drivers, several papers and proceedings detailing the optics, structure, and energy recovery systems, and more. Starting in January 2025, a new phase, with funding by the EU Horizons Europe program, began. This phase aims to consolidate plans for AtLAST and link the science cases to instrument concepts and requirements. In this talk, I will detail this effort and provide an overview of the tools we are developing to do this.