Bibcode
DOI
Berrier, Joel C.; Bullock, James S.; Barton, Elizabeth J.; Guenther, Heather D.; Zentner, Andrew R.; Wechsler, Risa H.
Bibliographical reference
The Astrophysical Journal, Volume 652, Issue 1, pp. 56-70.
Advertised on:
11
2006
Journal
Citations
98
Refereed citations
87
Description
The standard ΛCDM model predicts that the major merger rate of
galaxy-size dark matter halos rises rapidly with redshift. The average
number of close companions per galaxy, Nc, is often used to
infer the galaxy merger rate; however, recent observational studies
suggest that Nc evolves very little with redshift. Here we
use a ``hybrid'' N-body simulation plus analytic substructure model to
predict Nc directly. We identify dark matter subhalos with
galaxies and show that the observed lack of close-pair count evolution
arises because the high merger rate per halo at early times is
counteracted by a decrease in the number of halos massive enough to host
a galaxy pair. We compare our results to data compiled from the DEEP2,
SSRS2, and UZC redshift surveys. Observed pair counts match our
predictions if we assume a monotonic mapping between galaxy luminosity
and the maximum circular velocity that each subhalo had when it was
first accreted onto its host halo. This suggests that satellite galaxies
are significantly more resilient to mass loss than are dissipationless
dark matter subhalos. We argue that while Nc does not provide
a direct measure of the halo merger rate, it offers a powerful means to
constrain both the halo occupation distribution and the spatial
distribution of galaxies within halos. Interpreted in this way,
close-pair counts provide a useful test of galaxy formation processes on
~10-100 kpc scales.