Astro Seminar: "Large-Scale Structure Tests of Galaxy Formation and Modified Gravity"

Wed, 03/29/2017 - 14:00 - 15:00
Ying Zu (Ohio State University).

I will present novel tests of galaxy formation theories and the nature of gravity, using large-scale structure measurements from the Sloan Digital Sky Survey (SDSS). I will first introduce the iHOD model, a probabilistic framework for mapping galaxy properties to their underlying dark matter halos. By modelling the color dependence of galaxy clustering and weak gravitational lensing, iHOD reveals a surprisingly simple picture for "galaxy quenching", i.e., the cessation of star-formation activities within galaxies. In particular, the probability of a galaxy being quenched is strongly tied to the mass of its host halo, regardless of the stellar mass or halo formation time. This simple halo quenching model can also successfully explain the environmental dependence of colours, as measured by the mark correlations of colors, as well as the curious effect of color conformity.  Secondly, I will present an analytic description of the galaxy infall kinematics (GIK), empirically calibrated against N-body cosmological simulations. The GIK model accurately describes the velocity distribution from within the cluster inner region to beyond several tens of virial radii away from the cluster center. Most importantly, the average GIK can be reconstructed from the 2D cluster-galaxy cross-correlation function for any sample of clusters, therefore allowing for a dynamic estimate of the matter profile of clusters in the infall region. Comparing this dynamic mass estimate to the weak lensing mass measured for the same clusters would provide powerful constraint on theories of dark energy and any potential deviation of gravity from General Relativity on large scales.

David Rittenhouse Laboratory, A4