A panoramic mid-infrared survey of two distant clusters

J. E. Geach, Ian Smail, R. S. Ellis, S. M. Moran, G. P. Smith, T. Treu, J. P. Kneib, A. C. Edge, T. Kodama

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90 Citations (Scopus)

Abstract

We present panoramic Spitzer MIPS 24 μm observations, covering ∼9 × 9 Mpc2 (25′ ′ 25′) fields around two massive clusters, Cl 0024+16 and MS 0451-03, at z = 0.39 and z = 0.55, respectively, reaching a 5 σ flux limit of ∼200 μJy. Our observations cover a very wide range of environments within these clusters, from high-density regions around the cores out to the turnaround radius. Cross-correlating the mid-infrared catalogs with deep optical and near-infrared imaging of these fields, we investigate the optical/near-infrared colors of the mid-infrared sources. We find excesses of mid-infrared sources with the optical/near-infrared colors expected of cluster members in the two clusters and test this selection using spectroscopically confirmed 24 μm members. The much more significant excess is associated with Cl 0024+16, whereas MS 0451-03 has comparatively few mid-infrared sources. The mid-infrared galaxy population in Cl 0024+16 appears to be associated with dusty star-forming galaxies (typically redder than the general cluster population by up to Av ∼ 1-2 mag) rather than emission from dusty tori around active galactic nuclei in early-type hosts. We compare the star formation rates derived from the total infrared (8-1000 μm) luminosities for the mid-infrared sources in Cl 0024+16 with those estimated from a published Hα survey, finding rates ≳5 times those found from Hα, indicating significant obscured activity in the cluster population. Compared to previous mid-infrared surveys of clusters from z ∼ 0-0.5, we find evidence for strong evolution of the level of dust-obscured star formation in dense environments to z = 0.5, analogous to the rise in the fraction of optically selected star-forming galaxies seen in clusters and the field out to similar redshifts. However, there are clearly significant cluster-to-cluster variations in the populations of mid-infrared sources, probably reflecting differences in the intracluster media and recent dynamical evolution of these systems.

Original languageEnglish
Pages (from-to)661-672
Number of pages12
JournalAstrophysical Journal
Volume649
Issue number2 I
DOIs
Publication statusPublished - 2006 Oct 1

Keywords

  • Galaxies: clusters: general
  • Galaxies: starburst
  • Infrared: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Geach, J. E., Smail, I., Ellis, R. S., Moran, S. M., Smith, G. P., Treu, T., Kneib, J. P., Edge, A. C., & Kodama, T. (2006). A panoramic mid-infrared survey of two distant clusters. Astrophysical Journal, 649(2 I), 661-672. https://doi.org/10.1086/506469