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Merger Histories of Galaxy Halos and Implications for Disk Survival | | Kyle R. Stewart
; James S. Bullock
; Risa H. Wechsler
; Ariyeh H. Maller
; Andrew R. Zentner
; | | Date: |
30 Nov 2007 | | Abstract: | We study the merger histories of galaxy dark matter halos using a high
resolution LCDM N-body simulation. Our merger trees follow ~17,000 halos with
masses M_0 = (10^11--10^13) Msun at z=0 and track accretion events involving
objects as small as m = 10^10 Msun. We find that mass assembly is remarkably
self-similar in m/M_0, and dominated by mergers that are ~10% of the final halo
mass. While very large mergers, m > 0.4 M_0, are quite rare, sizeable accretion
events, m ~ 0.1 M_0, are common. Over the last 10 Gyr, an overwhelming majority
(~95%) of Milky Way-sized halos with M_0 = 10^12 Msun have accreted at least
one object with greater total mass than the Milky Way disk (m > 5x10^10 Msun),
and approximately 70% have accreted an object with more than twice that mass (m
> 10^11 Msun). Our results raise serious concerns about the survival of
thin-disk dominated galaxies within the current paradigm for galaxy formation
in a CDM universe. In order to achieve a ~70% disk-dominated fraction in Milky
Way-sized CDM halos, mergers involving m ~ 2x10^11 Msun objects must not
destroy disks. | | Source: | arXiv, 0711.5027 | | Services: | Forum | Review | PDF | Favorites | |
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