Publication details for Professor Ian SmailGeach, 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. The Astrophysical Journal 649(2): 661-672.
- Publication type: Journal Article
- ISSN/ISBN: 0004-637X, 1538-4357
- DOI: 10.1086/506469
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
Author(s) from Durham
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.