Schaerer, D. and Hempel, A. and Egami, E. and Pelló, R. and Richard, J. and Le Borgne, J.-F. and Kneib, J.-P. and Wise, M. and Boone, F. (2007) EROs found behind lensing clusters. I. Stellar populations and dust properties of optical dropout EROs and comparison with related objects. Astronomy and Astrophysics, 469 (1). pp. 47-60. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20100311-113740231
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Context. On the nature, redshift, stellar populations and dust properties of optically faint or non-detected extremely red objects. Aims. Determining the nature, redshift, stellar populations and dust properties of optically faint or non-detected, extremely red objects (ERO) found from our survey of the lensing clusters A1835 and AC114 (Richard et al. 2006, A&A, 456, 861). Comparison with properties of related galaxies, such as IRAC selected EROs and a z ~ 6.5 post-starburst galaxy candidate from the Hubble Ultra Deep Field. Methods. Using an updated version of Hyperz (Bolzonella et al. 2000, A&A, 363, 476) and a large number of spectral templates we perform broad-band SED fitting. The photometric observations, taken from Hempel et al. (2007, A&A, submitted), include deep optical, ACS/HST, ISAAC/VLT, IRAC/Spitzer data, and for some objects 24 m MIPS/Spitzer and sub-mm data as well. Results. For most of the lensed EROs we find photometric redshifts showing a strong degeneracy between "low-z" (z ~ 1-3) and high-z (z ~ 6-7). Although formally best fits are often found at high-z, their resulting bright absolute magnitudes, the number density of these objects, and in some cases Spitzer photometry or longer wavelength observations, suggest strongly that all of these objects are at "low-z". The majority of these objects are best fitted with relatively young (≲0.5-0.7 Gyr) and dusty starbursts. Three of our objects show indications for strong extinction, with A_V ~ 2.4-4. The typical stellar masses of our objects are M_* ~ (0.5-5) × 10^(10) M_☉ after correction for lensing; for the most extreme ERO in our sample, the sub-mm galaxy SMMJ14009+0252 most likely at z_(fit) ~ 3, we estimate M_* ~ 6. × 10^(11) M_☉. For dusty objects star formation rates (SFR) have been estimated from the bolometric luminosity determined after fitting of semi-empirical starburst, ERO, and ULIRG templates.Typically we find SFR ~ (1-18) M_☉ yr^(-1). Again, SMMJ14009+0252 stands out as a LIRG with SFR ~ 1000 M_☉ yr^(-1). Finally, we predict the mid-IR to sub-mm SED of the dusty objects for comparison with future observations with APEX, Herschel, and ALMA. Concerning the comparison objects, we argue that the massive post-starburst z ~ 6.5 galaxy candidate HUDF-J2 showing observed properties very similar to our EROs, is more likely a dusty starburst at z ~ 2.3-2.6. This interpretation also naturally explains the observed 24 m emission from this object and we predict its IR to sub-mm SED. Both empirically and from our SED fits we find that the IRAC selectec EROs from Yan et al. (2004, ApJ, 616, 63) show very similar properties to our lensed EROs. Reasonable fits are found for most of them with relatively young and dusty stellar populations.
|Additional Information:||© ESO 2007. Received 19 January 2007; accepted 13 March 2007. We have benefited from interesting discussions with numerous colleagues who we wish to collectively thank here. We thank Haojing Yan for private communication of MIPS data. Support from ISSI (Internation Space Science Institute) in Bern for an “International Team” is gratefully acknowledged. 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).|
|Subject Keywords:||galaxies: high-redshift; galaxies: evolution; galaxies: starburst; cosmology: early Universe; infrared: galaxies|
|Official Citation:||EROs found behind lensing clusters - I. Stellar populations and dust properties of optical dropout EROs and comparison with related objects D. Schaerer, A. Hempel, E. Egami, R. Pelló, J. Richard, J.-F. Le Borgne, J.-P. Kneib, M. Wise and F. Boone A&A 469 (1) 47-60 (2007) DOI: 10.1051/0004-6361:20077127|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||12 Mar 2010 17:32|
|Last Modified:||26 Dec 2012 11:50|
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