Journal Article

The distribution of ejected subhaloes and its implication for halo assembly bias

Huiyuan Wang, H. J. Mo and Y. P. Jing

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 4, pages 2249-2256
Published in print July 2009 | ISSN: 0035-8711
Published online July 2009 | e-ISSN: 1365-2966 | DOI:
The distribution of ejected subhaloes and its implication for halo assembly bias

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Using a high-resolution cosmological N-body simulation, we identify the ejected population of subhaloes, which are haloes at redshift z= 0 but were once contained in more massive ‘host’ haloes at high redshifts. The fraction of the ejected subhaloes in the total halo population of the same mass ranges from 9 to 4 per cent for halo masses from ∼1011 to ∼1012 h−1 M. Most of the ejected subhaloes are distributed within four times the virial radius of their hosts. These ejected subhaloes have distinct velocity distribution around their hosts in comparison to normal haloes. The number of subhaloes ejected from a host of given mass increases with the assembly redshift of the host. Ejected subhaloes in general reside in high-density regions, and have a much higher bias parameter than normal haloes of the same mass. They also have earlier assembly times, so that they contribute to the assembly bias of dark matter haloes seen in cosmological simulations. However, the assembly bias is not dominated by the ejected population, indicating that large-scale environmental effects on normal haloes are the main source for the assembly bias.

Keywords: methods: statistical; galaxies: haloes; dark matter; large-scale structure of Universe

Journal Article.  5489 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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