| Description |
Understanding how galaxies form and evolve is one of the most pressing questions in modern astronomy. The distribution of galaxies in the color-magnitude diagram (CMD) encodes key information on the physical processes in galaxy formation and evolution. A better understanding of the CMD would rely on connecting galaxy properties to the underlying dark matter halos. My work in this dissertation is to build a global connection between galaxy color/luminosity and halo mass, using the observed clustering of galaxies across the CMD and the theoretically predicted halo population. I first focus on the faint and red end of the CMD, where the observed clustering of such faint red galaxies was difficult to explain before. I present a method to improve the clustering measurement of faint galaxies and apply it to the faint red galaxy sample. It results in a 40 percent decrease in the fractional uncertainty of the clustering measurement on large scales, significantly alleviating the previous tension between the clustering strengths on small- and large-scales. I then model the new measurement within the halo occupation distribution (HOD) framework and find that a considerable fraction of those galaxies to be satellites in massive halos. By comparing the modeling results with semi-analytic model predictions, I discuss the implications on the evolution of such galaxies. To have a full view of the relation between galaxy color/luminosity and halos, I formulate a global model, the conditional color-magnitude distribution (CCMD), that describes the dependence of galaxy color/luminosity distribution on halo mass. I infer the CCMD parameter values by simultaneously fitting the space densities and auto-correlation functions of multiple galaxy samples from the Sloan Digital Sky Survey, defined by fine bins in the CMD. The modeling results reveal a wealth of information. For example, the bimodality of the color distribution is driven by central galaxies at most luminosities, and the satellite fraction is more sensitive to color than luminosity. The results have many implications for the galaxy-halo relation and galaxy formation models. They can lead to a variety of applications, such as testing galaxy group finding algorithm and constraining the galaxy assembly bias effect. |
