The evolution of the specific star formation rate of massive galaxies to z 1.8 in the extended chandra deep field south

Maaike Damen, Ivo Labbé, Marijn Franx, Pieter G. Van Dokkum, Edward N. Taylor, Eric J. Gawiser

Research output: Contribution to journalArticlepeer-review

119 Scopus citations


We study the evolution of the star formation rate (SFR) of mid-infrared selected galaxies in the extended Chandra Deep Field South. We use a combination of UBVRI z′JHK GaBoDS and MUSYC data, deep Infrared Array Camera observations from SIMPLE, and deep MIPS data from FIDEL. This unique multiwavelength data set allows us to investigate the SFR history of massive galaxies out to redshift z 1.8. We determine the SFRs using both the rest-frame ultraviolet luminosity from young, hot stars and the total infrared IR luminosity of obscured star formation obtained from the MIPS 24 μm flux. We find that at all redshifts the galaxies with higher masses have substantially lower specific SFRs (SSFRs) than lower-mass galaxies. The average SSFRs increase with redshift, and the rate of incline is similar for all galaxies (roughly (1 + z)n, n = 5.0 ± 0.4). It does not seem to be a strong function of galaxy mass. Using a subsample of galaxies with masses M * > 1011M, we measured the fraction of galaxies whose star formation is quenched. We consider a galaxy to be in quiescent mode when its SSFR does not exceed 1/(3 × tH ), where tH is the Hubble time. The fraction of quiescent galaxies defined as such decreases with redshift out to z 1.8. We find that, at that redshift, 19% ± 9% of the M* > 1011 M sources would be considered quiescent according to our criterion.

Original languageEnglish (US)
Pages (from-to)937-943
Number of pages7
JournalAstrophysical Journal
Issue number1
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: high-redshift
  • Infrared: galaxies Online-only material: color figures


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