This overview of our current understanding of the large-scale structure of the Universe has shown that quantitative measurements of the clustering and spatial distribution of galaxies have wide applications and implications. The non-uniform structure reveals properties of both the galaxies and the dark matter halos that comprise this large-scale structure. Statistics such as the two-point correlation function can be used not only to constrain cosmological parameters but also to understand galaxy formation and evolution processes. The advent of extremely large redshift surveys with samples of hundreds of thousands of galaxies has led to very precise measurements of the clustering of galaxies at z ~ 0.1 as a function of various galaxy properties such as luminosity, color, and stellar mass, influencing our understanding of how galaxies form and evolve. Initial studies at higher redshift have revealed that many of the general correlations that are observed between galaxy properties and clustering at z ~ 0 were in place when the Universe was a fraction of its current age. As larger redshift surveys are carried out at higher redshifts, much more can be learned about how galaxy populations change with time. Theoretical interpretations of galaxy clustering measurements such as the halo occupation distribution model have also recently made great strides in terms of statistically linking various properties of galaxies with those of their host dark matter halos. Such studies reveal not only how light traces mass on large scales but how baryonic mass and dark matter co-evolve with cosmic time.
There are many exciting future directions for studies of galaxy clustering and large-scale structure. Precise cosmological constraints can be obtained using baryon acoustic oscillation signatures observed in clustering measurements from wide-area surveys (Eisenstein et al. 2005). Specific galaxy populations can be understood in greater detail by comparing their clustering properties with those of galaxies in general. For example, the clustering of different types of active galactic nuclei (AGN) can be used to constrain the AGN fueling mechanisms, lifetimes, and host galaxy populations (Coil et al. 2009). As discussed above, measurements of galaxy clustering have the power to place strong constraints on contemporary models of galaxy formation and evolution and advance our understanding of how galaxies populate and evolve within dark matter halos.
The author thanks James Aird, Mirko Krumpe, and Stephen Smith for providing comments on earlier drafts of the text.