case western reserve university



The Effects of Environment on Galaxy Evolution in the Local Universe

Chris Miller (Carnegie Mellon University)

A fundamental goal of observational cosmology is to determine the spatial distribution of galaxies as a function of their physical properties e.g., luminosity, morphology, star formation rate, etc. Such observations place constraints on models of galaxy formation and evolution. For instance, it has been known for some time that star-forming galaxies avoid the densest regions in the Universe, indicating that the environment can quench the cool gas that fuels new stars. This same cool gas has been theorized to accrete onto a galaxy's central Super Massive Black Hole and light up an active galactic nucleus (AGN). Using a sample of AGNs 100 times larger than previous studies, I find that AGNs trace the same underlying large-scale structure in the local Universe as do all galaxies. Additionally, the rate of decreasing star-formation with density is independent of local environment. Combined, these results suggest that the environments around galaxies do not play a significant role in the global evolution of galactic bulges (as traced by AGNs) or spiral disks (as traced by star formation). I will discuss the significance of these results with respect to galaxy formation and evolution models.