Speaker
Description
This work consists of two parts. The first is the study of the galaxy population in the SDSS galaxy groups with DESI imaging data. The second is the study on how to measure galaxy abundance and clustering at high redshift from incomplete spectroscopic data.
In the first part, we use the most recent data release (DR9) of the DESI legacy imaging survey and SDSS galaxy groups to measure the conditional luminosity function (CLF) for groups with halo mass $M_{\rm h}> 10^{12}M_{\odot}$ and $0.01< z< 0.08$, down to $M_{\rm r}=-10\sim-12$. For a given halo mass we measure the CLF for the total satellite population, as well as separately for the red and blue populations classified using the $(g-z)$ color. We find a clear faint-end upturn in the CLF of red satellites, with a slope $\alpha\approx-1.8$ which is almost independent of halo mass. Our stellar population synthesis modeling shows that the $(g-z)$ color provides a clean red/blue division, and that group galaxies in the red population defined by $(g-z)$ are all dominated by old stellar populations. The fraction of old galaxies as a function of galaxy luminosity shows a minimum at a luminosity $M_{\rm r}\sim-18$, corresponding to a stellar mass $M_\ast\sim10^{9.5}M_\odot$. This mass scale is independent of halo mass and is comparable to the characteristic luminosity at which galaxies show a dichotomy in surface brightness and size, suggesting that the dichotomy in the old fraction and in galaxy structure may have a common origin.
In the second part, we use the mock samples to study the influence of the selection effects in high redshift spectroscopic surveys on the measurements of galaxy abundance and clustering. We show that target selection and redshift incompleteness can lead to significantly biased results, especially due to the flux limit selection criteria, using realistic mock catalogs. We develop a new method to correct the flux limit effect, using information provided by the parent photometric data from which the spectroscopic sample is constructed. Our tests using realistic mock samples show that our methods are able to reproduce the true stellar mass function and correlation function reliably. Mock catalogs are constructed for the existing surveys zCOSMOS and VIPERS, as well as the forthcoming PFS galaxy evolution survey. The same set of mock samples are used to quantify the total variance expected for different sample sizes. We find that the total variance decreases very slowly when the survey area reach 4 deg$^2$ for abundance and 8 deg$^2$ for clustering, indicating that cosmic variance is no longer the dominant source of error for PFS-like surveys. The relative error in the PFS-like galaxy survey will be significantly smaller than the current zCOSMOS and VIPERS survey.
