| The biased relation between the galaxy and mass distributions lies at the intersection of large scale structure in the universe and the process of galaxy formation. I study the nature of galaxy bias and its connections to galaxy clustering and galaxy formation physics.; Galaxy bias has traditionally been viewed as an obstacle to constraining cosmological parameters by studying galaxy clustering. I examine the effect of bias on measurements of the cosmological density parameter by techniques that exploit the gravity-induced motions of galaxies. Using a variety of environmental bias models applied to N-body simulations, I find that, in most cases, the quantity estimated by these techniques is the value of , where is the ratio of rms galaxy fluctuations to rms mass fluctuations on large scales. Moreover, I find that different methods should, in principle, agree with each other and it is thus unlikely that non-linear or scale-dependent bias is responsible for the discrepancies that exist among current measurements.; One can also view the influence of bias on galaxy clustering as a strength rather than a weakness, since it provides us with a potentially powerful way to constrain galaxy formation theories. With this goal in mind, I develop the “Halo Occupation Distribution” (HOD), a physically motivated and complete formulation of bias that is based on the distribution of galaxies within virialized dark matter halos. I explore the sensitivity of galaxy clustering statistics to features of the HOD and focus on how the HOD may be empirically constrained from galaxy clustering data. I make the connection to the physics of galaxy formation by studying the HOD predicted by the two main theoretical methods of modeling galaxy formation. I find that, despite many differences between them, the two methods predict the same HOD, suggesting that galaxy bias is determined by robust features of the hierarchical galaxy formation process rather than details of gas cooling and star formation. |
