Dependence of Halo Properties on Interaction History, Environment, and Cosmology

I present results from numerical N-body simulations regarding the effect of merging events on the angular momentum distribution of galactic halos as well as a comparison of halo growth in semi-analytic vs. N-body methods. A total of six simulations are used spanning 3 cosmologies. In each model, one run was conducted using a spatially uniform grid of and one using a refined grid in a large void. In all three models, the interpretation most consistent with the data is that the orbital angular momentum of the interactors is important in establishing the final angular momentum of the merger product, although this conclusion is at odds with previous studies. I give the proper angular momentum distribution that should be used to describe merger remnants. I trace the most massive progenitor of L_* galactic-mass halos from redshift z=0 back to z=5 in the uniform grid simulations and for 10¹¹ solar mass halos in void regions. Semi-analytic mass histories match reasonably well for the latter sample. However, I find that for halos of mass 10¹² < M < 10¹⁴ solar masses, the semi-analytic method underestimates the mass of progenitors and hence the formation redshift of halos in simulations. These results are independent of \δ_c.