Luminous red galaxies in clusters: Central occupation, spatial distributions and miscentring

Hanako Hoshino, Alexie Leauthaud, Claire Lackner, Chiaki Hikage, Eduardo Rozo, Eli Rykoff, Rachel Mandelbaum, Surhud More, Anupreeta More, Shun Saito, Benedetta Vulcani

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


Luminous red galaxies (LRG) from the Sloan Digital Sky Survey are among the best understood samples of galaxies and are employed in a broad range of cosmological studies. In this paper, we study how LRGs occupy massive haloes via counts in clusters and reveal several unexpected trends. Using the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) cluster catalogue, we derive the central occupation of LRGs as a function richness. We show that clusters contain a significantly lower fraction of central LRGs than predicted from the two-point correlation function. At halo masses of 1014.5M, we find Ncen = 0.73 compared to Ncen = 0.89 from correlation studies. Our central occupation function for LRGs converges to 0.95 at large halo masses. A strong anticorrelation between central luminosity and cluster mass at fixed richness is required to reconcile our results with those based on clustering studies. We derive the probability that the brightest cluster member is not the central galaxy. We find PBNC ≈ 20-30 per cent which is a factor of ~2 lower than the value found by Skibba et al. Finally, we study the radial offsets of bright non-central LRGs from cluster centres and show that bright non-central LRGs follow a different radial distribution compared to red cluster members. This work demonstrates that even the most massive clusters do not always have an LRG at the centre, and that the brightest galaxy in a cluster is not always the central galaxy.

Original languageEnglish (US)
Pages (from-to)998-1013
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Apr 28 2015


  • Galaxies: clusters: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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