Exploring galaxy environments on large and small scales

I examine galaxy environments and galaxy interactions using ΛCDM N-body simulations, redshift surveys, and a sample of 77 galaxies in close pairs and groups. I show that some simulations and models for assigning luminosities to dark matter halos reproduce the observed counts-in-cylinders statistic distribution quite well, except for very isolated galaxies. I also find that the close-pair fraction from a ΛCDM simulation matches both the observed close-pair count at z=0 and the pair fraction evolution. Finally, I use U and V photometry of a sample of previously-studied galaxies to support results suggesting a relationship between galaxy separation and starburst strength, and confirm that U-B colors are a sensitive indicator of burst strength. This will be useful in studies of high redshift galaxies.