Speaker
Description
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.
| Would you be interested in presenting a poster if the conference is oversubcribed? | Yes |
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