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The accretion of galaxies into groups and clusters

McGee, SL and Balogh, ML and Bower, RG and Font, AS and McCarthy, IG (2009) The accretion of galaxies into groups and clusters. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 400 (2). pp. 937-950. ISSN 0035-8711

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We use the galaxy stellar mass and halo merger tree information from the semi-analyticmodel galaxy catalogue of Font et al. (2008) to examine the accretion of galaxies into a large sample of groups and clusters, covering a wide range in halo mass (1012.9 to 1015.3 h−1 M⊙), and selected from each of four redshift epochs (z=0, 0.5, 1.0 and 1.5). We find that clusters at all examined redshifts have accreted a significant fraction of their final galaxy populations through galaxy groups. A 1014.5 h−1 M⊙ mass cluster at z=0 has, on average, accreted_ 40%
of its galaxies (Mstellar > 109 h−1 M⊙) from halos with masses greater than 1013 h−1 M⊙. Further, the galaxies which are accreted through groups are more massive, on average, than galaxies accreted through smaller halos or from the field population. We find that at a given
epoch, the fraction of galaxies accreted from isolated environments is independent of the final cluster or group mass. In contrast, we find that observing a cluster of the same halo mass at each redshift epoch implies different accretion rates of isolated galaxies, from 5-6 % per Gyr
at z=0 to 15% per Gyr at z=1.5. We find that combining the existence of a Butcher Oemler effect at z=0.5 and the observations that galaxies within groups display significant environmental effects with galaxy accretion histories justifies striking conclusions. Namely, that the
dominant environmental process must begin to occur in halos of 1012 – 1013 h−1 M⊙, and act over timescales of > 2 Gyrs. This argues in favor of a mechanism like “strangulation”, in which the hot halo of a galaxy is stripped upon infalling into a more massive halo . This
simple model predicts that by z=1.5 galaxy groups and clusters will display little to no environmental effects. This conclusion may limit the effectiveness of red sequence cluster finding methods at high redshift.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record MNRAS (2009) 400(2): 937-95, "The accretion of galaxies into groups and clusters" is available online at:http://dx.doi.org/10.1111/j.1365-2966.2009.15507.x
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
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Date Deposited: 28 May 2015 13:43
Last Modified: 25 Jun 2015 12:39
DOI or Identification number: 10.1111/j.1365-2966.2009.15507.x
URI: http://researchonline.ljmu.ac.uk/id/eprint/1316

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