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Dark matter halo occupation: environment and clustering

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journal contribution
posted on 01.06.2011, 00:00 by Rupert CroftRupert Croft, Tiziana Di MatteoTiziana Di Matteo, Nishikanta Khandai, Volker Springel, Anirban JanaAnirban Jana, Jeffrey Gardner

We use a large dark matter simulation of a Λ cold dark matter (ΛCDM) model to investigate the clustering and environmental dependence of the number of substructures in a halo. Focusing on redshift z = 1, we find that the halo occupation distribution is sensitive at the tens of per cent level to the surrounding density and to a lesser extent to asymmetry of the surrounding density distribution. We compute the autocorrelation function of haloes as a function of occupation, building on the finding of Wechsler et al. and Gao & White that haloes (at fixed mass) with more substructure are more clustered. We compute the relative bias as a function of occupation number at fixed mass, finding a strong relationship. At fixed mass, haloes in the top 5 per cent of occupation can have an autocorrelation function ∼1.5–2 times higher than the mean. We also compute the bias as a function of halo mass, for fixed halo occupation. We find that for group- and cluster-sized haloes, when the number of subhaloes is held fixed, there is a strong anticorrelation between bias and halo mass. Such a relationship represents an additional challenge to the halo model.


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© 2012 The Authors, Published by the Royal Astronomical Society



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