AN INCREASING STELLAR BARYON FRACTION in BRIGHT GALAXIES at HIGH REDSHIFT

Steven L. Finkelstein, Mimi Song, Peter Behroozi, Rachel Somerville, Casey Papovich, Miloš Milosavljević, Avishai Dekel, Desika Narayanan, Matthew L.N. Ashby, Asantha Cooray, Giovanni G. Fazio, Henry C. Ferguson, Anton M. Koekemoer, Brett Salmon, S. P. Willner

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Recent observations have shown that the characteristic luminosity of the rest-frame ultraviolet (UV) luminosity function does not significantly evolve at 4 < z < 7 and is approximately We investigate this apparent non-evolution by examining a sample of 173 bright, MUV < -21 galaxies at z = 4-7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that galaxies at z = 4-7 have similar stellar masses of log(M/Mo) = 9.6-9.9 and are thus relatively massive for these high redshifts. However, bright galaxies at z = 4-7 are less massive and have younger inferred ages than similarly bright galaxies at z = 2-3, even though the two populations have similar star formation rates and levels of dust attenuation for a fixed dust-attenuation curve. Matching the abundances of these bright z = 4-7 galaxies to halo mass functions from the Bolshoi ΛCDM simulation implies that the typical halo masses in galaxies decrease from log(Mh/Mo) = 11.9 at z = 4 to log(Mh/Mo) = 11.4 at z = 7. Thus, although we are studying galaxies at a similar stellar mass across multiple redshifts, these galaxies live in lower mass halos at higher redshift. The stellar baryon fraction in galaxies in units of the cosmic mean Ωbm rises from 5.1% at z = 4 to 11.7% at z = 7; this evolution is significant at the ∼3σ level. This rise does not agree with simple expectations of how galaxies grow, and implies that some effect, perhaps a diminishing efficiency of feedback, is allowing a higher fraction of available baryons to be converted into stars at high redshifts.

Original languageEnglish (US)
Article number95
JournalAstrophysical Journal
Volume814
Issue number2
DOIs
StatePublished - Dec 1 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • early universe
  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift
  • ultraviolet: galaxies

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