The XMM Cluster Survey: The Halo Occupation Number of BOSS galaxies in X-ray clusters

Nicola Mehrtens, A. Kathy Romer, Robert C. Nichol, Chris A. Collins, Martin Sahlén, Philip J. Rooney, Julian A. Mayers, A. Bermeo-Hernandez, Martyn Bristow, Diego Capozzi, L. Christodoulou, Johan Comparat, Matt Hilton, Ben Hoyle, Scott T. Kay, Andrew R. Liddle, Robert G. Mann, Karen Masters, Christopher J. Miller, John K. ParejkoFrancisco Prada, Ashley J. Ross, Donald P. Schneider, John P. Stott, Alina Streblyanska, Pedro T. P. Viana, Martin White, Harry Wilcox, Idit Zehavi

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We present a direct measurement of the mean halo occupation distribution (HOD) of galaxies taken from the eleventh data release (DR11) of the Sloan Digital Sky Survey-III Baryon Acoustic Oscillation Survey (BOSS). The HOD of BOSS low-redshift (LOWZ: 0.2 <z <0.4) and Constant-Mass (CMASS: 0.43 <z <0.7) galaxies is inferred via their association with the dark-matter halos of 174 X-ray-selected galaxy clusters drawn from the XMM Cluster Survey (XCS). Halo masses are determined for each galaxy cluster based on X-ray temperature measurements, and range between log10(M180/M⊙) = 13 - 15. Our directly-measured HODs are consistent with the HOD-model fits inferred via the galaxy-clustering analyses of Parejko et al. (2013) for the BOSS LOWZ sample and White et al. (2011) for the BOSS CMASS sample. Under the simplifying assumption that the other parameters that describe the HOD hold the values measured by these authors, we have determined a best-fit alpha-index of 0.91±0.08 and 1.27^{+0.03}_{-0.04} for the CMASS and LOWZ HOD, respectively. These alpha-index values are consistent with those measured by White et al. (2011) and Parejko et al. (2013). In summary, our study provides independent support for the HOD-models assumed during the development of the BOSS mock-galaxy catalogues that have subsequently been used to derive BOSS cosmological constraints.
Original languageEnglish
Pages (from-to)1929-1943
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date30 Aug 2016
Publication statusPublished - 1 Dec 2016


  • X-rays: galaxies: clusters
  • galaxies: haloes


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