Reversal of fortune: Confirmation of an increasing star formation-density relation in a cluster at z = 1.62

Kim Vy H. Tran, Casey Papovich, Amélie Saintonge, Mark Brodwin, James S. Dunlop, Duncan Farrah, Keely D. Finkelstein, Steven L. Finkelstein, Jennifer Lotz, Ross J. McLure, Ivelina Momcheva, Christopher N.A. Willmer

Research output: Contribution to journalArticlepeer-review

193 Scopus citations


We measure the rest-frame colors (dust-corrected), infrared luminosities, star formation rates, and stellar masses of 92 galaxies in a Spitzer-selected cluster at z = 1.62. By fitting spectral energy distributions (SEDs) to 10-band photometry (0.4μm< λobs < 8μm) and measuring 24μm fluxes for the 12 spectroscopically confirmed and 80 photometrically selected members, we discover an exceptionally high level of star formation in the cluster core of ∼1700M yr-1 Mpc -2. The cluster galaxies define a strong blue sequence in (U-V ) color and span a range in color. We identify 17 members with LIR > 1011 L, and these IR luminous members follow the same trend of increasing star formation with stellar mass that is observed in the field at z ∼ 2. Using rates derived from both the 24μm imaging and SED fitting, we find that the relative fraction of star-forming members triples from the lowest to highest galaxy density regions; e.g., the IR luminous fraction increases from ∼8% at ∑ ∼ 10 gal Mpc-2 to ∼25% at ∑ ≳ 100 gal Mpc-2. The observed increase is a reversal of the well-documented trend at z < 1 and signals that we have reached the epoch when massive cluster galaxies are still forming a substantial fraction of their stars.

Original languageEnglish (US)
Pages (from-to)L126-L129
JournalAstrophysical Journal Letters
Issue number2 PART 2
StatePublished - Aug 20 2010


  • Galaxies: clusters: individual (ClG J0218.3-0510)
  • Galaxies: evolution
  • Galaxies: starburst
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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