2000/06/30 by Jeffrey P. Gardner · 3 citations
Physics and Astronomy · #Angular momentum #Angular momentum coupling #Astronomy and Astrophysical Research #Astrophysics #Classical mechanics #Cosmology #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Mass distribution #Physics #Population #Redshift #Specific relative angular momentum #Stellar, planetary, and galactic studies #Total angular momentum quantum number #astro-ph
paper · pdf · doi:10.1086/321631
17 pages, 7 postscript figures. Final version, accepted by ApJ
arxiv created 2001/05/18 · openalex publication_date 2001/08/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 Press-Schechter versus N -body methods. A total of six simulations are used, spanning three cosmologies: a standard flat Ω 0 = 1 model, an open Ω 0 = 0.3 model, and a "tilted" flat Ω 0 = 1 model with spectral index n = 0.8. In each model, one run was conducted using a spatially uniform grid of particles and one using a refined grid in a large void. In all three models and all environments tested, the mean angular momentum of merger remnants (halo interaction products with mass ratios 3 : 1 or less) is greater than nonmerger remnants. Furthermore, the dispersion in the merger-remnant angular momentum distribution is smaller than the dispersion of the nonmerger distribution. 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. I give the angular momentum distribution, which describes the merger remnant population. I trace the most massive progenitor of L * galactic-mass halos (uniform grid) and 10 11 M ☉ halos (refined void) from z = 0 back to z = 5. Monte Carlo mass histories match simulations reasonably well for the latter sample. I find that for halos of mass 10 12 ≲ M ≲ 10 14 M ☉ , this method can underestimate the mass of progenitors by 20%, hence yielding improper formation redshifts of halos. With this caveat, however, the general shapes of halo mass histories and formation time distributions are preserved.