Early formation and late merging of the giant galaxies

被引:88
作者
Gao, L [1 ]
Loeb, A
Peebles, PJE
White, SDM
Jenkins, A
机构
[1] Max Planck Inst Astrophys, D-85748 Garching, Germany
[2] Harvard Univ, Dept Astron, Cambridge, MA 02138 USA
[3] Princeton Univ, Joseph Henry Labs, Princeton, NJ 08544 USA
[4] Univ Durham, Dept Phys, Inst Computat Cosmol, Durham DH1 3LE, England
关键词
cosmology : theory; galaxies : formation; galaxies : interactions; galaxies : structure; stellar dynamics;
D O I
10.1086/423444
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The most luminous galaxies in the present universe are found at the centers of the most massive dark matter halos: rich galaxy clusters. In the LambdaCDM cosmology, such massive halo cores are present at redshift z = 6 with a comoving number density (as a function of mass interior to similar to10 kpc) that is comparable to today's value. The identity of the matter in these central regions is, however, predicted to change as major mergers bring together stars and dark matter from initially well-separated subunits. We use N-body simulations to investigate how these mergers push preexisting matter outward in the dominant galaxy while preserving the inner density profile of collisionless matter. It appears that the central regions of large galaxies end up dominated by stars formed in a number of dense cores, well before the last major mergers. The density profile of collisionless matter ( stars and dark matter combined) in these central regions appears to be stable and to have attractor-like behavior under merging. This suggests that the baryon loading associated with dissipative contraction and star formation may be erased as subsequent mergers drive the mass distribution back to a universal profile. Such suppression of the effects of baryon loading, along with the early assembly of mass concentrations, may help resolve some apparent challenges to the CDM model for structure formation.
引用
收藏
页码:17 / 25
页数:9
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