Galaxy clusters in the IRAC Dark Field. I. Growth of the Red Sequence

Creators: Krick, J. E.; Surace, J. A.; Thompson, D.; Ashby, M. L. N.; Hora, J. L.; Gorjian, V.; Yan, L.

Abstract

Using three newly identified galaxy clusters at z ~ 1 (photometric redshift) we measure the evolution of the galaxies within clusters from high redshift to the present day by studying the growth of the red cluster sequence. The clusters are located in the Spitzer Infrared Array Camera (IRAC)Dark Field, an extremely deep mid-infrared survey near the north ecliptic pole with photometry in 18 total bands from X-ray through far-IR. Two of the candidate clusters are additionally detected as extended emission in matching Chandra data in the survey area, allowing us to measure their masses to be M_(500) = (6.2 ± 1.0) x 10^(13) and (3.6 ± 1.1) x 10^(13)M_☉. For all three clusters we create a composite color-magnitude diagram in rest-frame B - K using our deep HST and Spitzer imaging. By comparing the fraction of low-luminosity member galaxies on the composite red sequence with the corresponding population in local clusters at z = 0.1 taken from COSMOS, we examine the effect of a galaxy's mass on its evolution.We find a deficit of faint galaxies on the red sequence in our z ~ 1 clusters, which implies that more massive galaxies have evolved in clusters faster than less massive galaxies, and that the less massive galaxies are still forming stars in clusters such that they have not yet settled onto the red sequence.

Additional Information

© 2008 The American Astronomical Society. Received 2008 May 30, accepted for publication 2008 July 9. We acknowledge E. Rykoff for help with the mass measurement. We thank the anonymous referee for useful suggestions on the manuscript. This research has made use of data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work was based on observations obtained with the Hale Telescope, Palomar Observatory, as part of a continuing collaboration between the California Institute of Technology, NASA/JPL, and Cornell University; the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA; the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona; and the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5- 26555. These observations are associated with program 10521, support of which was provided by NASA through a grant from the Space Telescope Science Institute. Facilities: Akari, CXO(ACIS), Hale (LFC, WIRC), HST(ACS), MMT(Megacam), Spitzer( IRAC, MIPS)

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