The integrated stellar content of dark matter halos

Alexie Leauthaud, Matthew R. George, Peter S. Behroozi, Kevin Bundy, Jeremy Tinker, Risa H. Wechsler, Charlie Conroy, Alexis Finoguenov, Masayuki Tanaka

Research output: Contribution to journalArticlepeer-review

96 Scopus citations


Measurements of the total amount of stars locked up in galaxies as a function of host halo mass contain key clues about the efficiency of processes that regulate star formation. We derive the total stellar mass fraction f (excluding stars in the intracluster light) as a function of halo mass M500c from z = 0.2 to z = 1 using two complementary methods. First, we derive f using a statistical Halo Occupation Distribution model jointly constrained by data from lensing, clustering, and the stellar mass function. This method enables us to probe f over a much wider halo mass range than with group or cluster catalogs. Second, we derive f at group scales using a COSMOS X-ray group catalog and show that the two methods agree to within 30%. We quantify the systematic uncertainty on f using abundance matching methods and show that the statistical uncertainty on f (10%) is dwarfed by systematic uncertainties associated with stellar mass measurements (45% excluding initial mass function, IMF, uncertainties). Assuming a Chabrier IMF, we find 0.012 ≤ f ≤ 0.025 at M500c = 10 13 M and 0.0057 ≤ f ≤ 0.015 at M500c = 1014 M. These values are significantly lower than previously published estimates. We investigate the cause of this difference and find that previous work has overestimated f owing to a combination of inaccurate stellar mass estimators and/or because they have assumed that all galaxies in groups are early-type galaxies with a constant mass-to-light ratio. Contrary to previous claims, our results suggest that the mean value of f is always significantly lower than fgas for halos above 1013 M . Combining our results with recently published gas mass fractions, we find a shortfall in f + fgas at R 500c compared to the cosmic mean. This shortfall varies with halo mass and becomes larger toward lower halo masses.

Original languageEnglish (US)
Article number95
JournalAstrophysical Journal
Issue number1
StatePublished - Feb 10 2012
Externally publishedYes


  • X-rays: galaxies: clusters
  • cosmology: observations
  • diffuse radiation
  • galaxies: clusters: general
  • galaxies: stellar content

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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