Hempel, A. and Schaerer, D. and Egami, E. and Pelló, R. and Wise, M. and Richard, J. and Le Borgne, J.-F. and Kneib, J.-P. (2008) EROs found behind lensing clusters. II. Empirical properties, classification, and SED modelling based on multi-wavelength observations. Astronomy and Astrophysics, 477 (1). pp. 55-66. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:HEMaanda08
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Aims. We study the properties and nature of extremely red galaxies (FRO, R-K >= 5.6) found behind two lensing clusters and compare them with other known galaxy populations. Methods. New HST/ACS, Spitzer (TRAC and MIPS), and Chandra/ACIS observations of the two lensing clusters Abell 1835 and AC 114 have been obtained, combined with our earlier optical and near-IR observations and used to study EROs in these deep fields. Results. We have found 6 and 9 EROs in Abell 1835 and AC 114. Several (7) of these objects are undetected up to the I and/or Z(850) band, and are hence "optical" drop-out sources (at a 3(T limit). The photometric redshifts of most of our sources (80%) are z similar to 0.7-1.5. According to simple colour-colour diagrams, the majority of our objects would be classified as hosting old stellar populations ("ellipticals"). However, there are clear signs of dusty starbursts for several among them. These objects correspond to the most extreme ones in R - K colour. After correcting for lens magnification, we estimate a surface density of (0.97 +/- 0.31) arcmin^(-2) for EROs with (R - K >= 5.6) at K < 20.5. As in earlier Studies, an overlap of different populations is found. Among our 15 EROs 6 (40%) also classify as distant red galaxies. Eleven of 13 EROs (85%) with available IRAC photometry also fulfil the selection criteria for TRAC selected EROs (IEROs) of Yan et al. (2004, ApJ, 616, 63). SED modelling shows that similar to 36% of the IEROs in our sample are luminous or Ultra-luminous infrared galaxies ((U)LIRG). Some very red DRGs are found to be very dusty starbursts, even (U)LIRGs. No AGNs is found, although faint activity cannot be excluded for all objects. From mid-IR and X-ray data, 5 objects are clearly classified as starbursts. The derived properties are quite similar to those of DRGs and IEROs, except for 5 extreme objects in terms of colours, for which a very high extinction (Av ≳ 3) is found.
|Additional Information:||© ESO 2008. Received 3 April 2007. Accepted 30 August 2007. We thank Andrea Grazian for providing us with the GOODS-MUSIC catalogues and Graham Smith for making their results available in electronic format. Support from ISSI (International Space Science Institute) in Bern for an "International Team'' is kindly acknowledged. Part of this work was supported by the Swiss National Science Foundation, the French Centre National de la Recherche Scientifique, and the French Programme National de Cosmologie (PNC) and Programme National de Galaxies (PNG). This paper is based on observations collected at the European Space Observatory, Chile (069.A-0508,070.A-0355,073.A-0471), and the Canada-France-Hawaii Telescope operated by the National Research Council of Canada, the French Centre National de la Recherche Scientifique (CNRS) and the University of Hawaii, and the NASA/ESA Hubble Space Telescope operated by the Association of Universities for Research in Astronomy, Inc., the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407, and the Chandra satellite. This research was supported in part by Chandra General Observer Program grant GO6-7106X. Based on observations collected at the Very Large Telescope (Antu/UT1), European Southern Observatory, Paranal, Chile (ESO Programs 69.A-0508, 70.A-0355, 73.A-0471), the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute which is operated by AURA under NASA contract NAS5-26555, the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407, and the Chandra satellite.|
|Subject Keywords:||galaxies: high-redshift; galaxies: starburst; infrared: galaxies; galaxies: evolution|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||11 Feb 2009 04:29|
|Last Modified:||26 Dec 2012 10:47|
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