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.
