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Published December 20, 2013 | Published + Submitted
Journal Article Open

The Era of Star Formation in Galaxy Clusters


We analyze the star formation properties of 16 infrared-selected, spectroscopically confirmed galaxy clusters at 1 < z < 1.5 from the Spitzer/IRAC Shallow Cluster Survey (ISCS). We present new spectroscopic confirmation for six of these high-redshift clusters, five of which are at z > 1.35. Using infrared luminosities measured with deep Spitzer/Multiband Imaging Photometer for Spitzer observations at 24 μm, along with robust optical + IRAC photometric redshifts and spectral-energy-distribution-fitted stellar masses, we present the dust-obscured star-forming fractions, star formation rates, and specific star formation rates in these clusters as functions of redshift and projected clustercentric radius. We find that z ~ 1.4 represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster star formation at earlier times. Beyond this redshift, the fraction of star-forming cluster members increases monotonically toward the cluster centers. Indeed, the specific star formation rate in the cores of these distant clusters is consistent with field values at similar redshifts, indicating that at z > 1.4 environment-dependent quenching had not yet been established in ISCS clusters. By combining these observations with complementary studies showing a rapid increase in the active galactic nucleus (AGN) fraction, a stochastic star formation history, and a major merging episode at the same epoch in this cluster sample, we suggest that the starburst activity is likely merger-driven and that the subsequent quenching is due to feedback from merger-fueled AGNs. The totality of the evidence suggests we are witnessing the final quenching period that brings an end to the era of star formation in galaxy clusters and initiates the era of passive evolution.

Additional Information

© 2013 American Astronomical Society. Received 2013 August 12; accepted 2013 October 19; published 2013 December 3. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Support for HST programs 10496, 11002, 11597, and 11663 were provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is based in part on observations obtained with the Chandra X-ray Observatory, under contract SV4-74018, A31 with the Smithsonian Astrophysical Observatory which operates the Chandra X-ray Observatory for NASA. Support for this research was provided by NASA grant G09-0150A. This work is based in part on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This work makes use of image data from the NOAO Deep Wide-Field Survey (NDWFS) as distributed by the NOAO Science Archive. NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation. We are grateful to the referee for a helpful report that improved the clarity of the paper. We thank P. Santini for providing her data in a digital form. We appreciate several useful conversations with C. Papovich, M. Cooper, M. Dickinson, N. Reddy, and S. Salim. This paper would not have been possible without the efforts of the support staffs of the Spitzer Space Telescope, Hubble Space Telescope, Chandra X-ray Observatory, and W. M. Keck Observatory.

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Published - 0004-637X_779_2_138.pdf

Submitted - 1310.6039v1.pdf


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