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The Optical Spectra of Spitzer 24 μm Galaxies in the Cosmic Evolution Survey Field. II. Faint Infrared Sources in the zCOSMOS-Bright 10k Catalog

Caputi, K. I. and Lilly, S. J. and Aussel, H. and Le Floc'h, E. and Sanders, D. and Maier, C. and Frayer, D. and Carollo, C. M. and Contini, T. and Kneib, J.-P. and Le Fèvre, O. and Mainieri, V. and Renzini, A. and Scodeggio, M. and Scoville, N. and Zamorani, G. and Bardelli, S. and Bolzonella, M. and Bongiorno, A. and Coppa, G. and Cucciati, O. and de la Torre, S. and de Ravel, L. and Franzetti, P. and Garilli, B. and Ilbert, O. and Iovino, A. and Kampczyk, P. and Kartaltepe, J. and Knobel, C. and Kovač, K. and Lamareille, F. and Le Borgne, J.-F. and Le Brun, V. and Mignoli, M. and Peng, Y. and Pérez-Montero, E. and Ricciardelli, E. and Salvato, M. and Silverman, J. and Surace, J. and Tanaka, M. and Tasca, L. and Tresse, L. and Vergani, D. and Zucca, E. and Abbas, U. and Bottini, D. and Capak, P. and Cappi, A. and Cassata, P. and Cimatti, A. and Elvis, M. and Hasinger, G. and Koekemoer, A. M. and Leauthaud, A. and Maccagni, D. and Marinoni, C. and McCracken, H. and Memeo, P. and Meneux, B. and Oesch, P. and Pellò, R. and Porciani, C. and Pozzetti, L. and Scaramella, R. and Scarlata, C. and Schiminovich, D. and Taniguchi, Y. and Zamojski, M. (2009) The Optical Spectra of Spitzer 24 μm Galaxies in the Cosmic Evolution Survey Field. II. Faint Infrared Sources in the zCOSMOS-Bright 10k Catalog. Astrophysical Journal, 707 (2). pp. 1387-1403. ISSN 0004-637X.

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We have used the zCOSMOS-bright 10k sample to identify 3244 Spitzer/MIPS 24 μm-selected galaxies with 0.06 mJy < S_(24 μm) ≾ 0.50 mJy and I_(AB) < 22.5, over 1.5 deg^2 of the COSMOS field, and studied different spectral properties, depending on redshift. At 0.2 < z < 0.3, we found that different reddening laws of common use in the literature explain the dust extinction properties of ~80% of our infrared (IR) sources, within the error bars. For up to 16% of objects, instead, the Hα λ6563/Hβ λ4861 ratios are too high for their IR/UV attenuations, which is probably a consequence of inhomogeneous dust distributions. In only a few of our galaxies at 0.2 < z < 0.3, the IR emission could be mainly produced by dust heated by old rather than young stars. Besides, the line ratios of ~22% of our galaxies suggest that they might be star-formation/nuclear-activity composite systems. At 0.5 < z < 0.7, we estimated galaxy metallicities for 301 galaxies: at least 12% of them are securely below the upper-branch mass-metallicity trend, which is consistent with the local relation. Finally, we performed a combined analysis of the Hδ equivalent width versus D_n (4000) diagram for 1722 faint and bright 24 μm galaxies at 0.6 < z < 1.0, spanning two decades in mid-IR luminosity. We found that, while secondary bursts of star formation are necessary to explain the position of the most luminous IR galaxies in that diagram, quiescent, exponentially declining star formation histories can well reproduce the spectral properties of ~40% of the less luminous sources. Our results suggest a transition in the possible modes of star formation at total IR luminosities L_(TIR) ≈ (3 ± 2) × 10^(11) L_⊙.

Item Type:Article
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URLURL TypeDescription DOIArticle
Surace, J.0000-0001-7291-0087
Additional Information:© 2009 The American Astronomical Society. Received 2009 September 8; accepted 2009 November 2; published 2009 December 4. This paper is based on observations made with the VIMOS spectrograph on the Melipal-VLT telescope, undertaken at the European Southern Observatory (ESO) under Large Program 175.A-0839. This paper is also based on observations made with the Spitzer Observatory, which is operated by the Jet Propulsion Laboratory, California Institute ofTechnology, under NASA contract 1407. We thank the anonymous referee for a constructive report of this paper.
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
European Southern Observatory (ESO) 175.A-0839
Subject Keywords:galaxies: abundances; galaxies: active; galaxies: evolution; galaxies: starburst; infrared: galaxies
Record Number:CaltechAUTHORS:20100111-110435619
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Official Citation:The Optical Spectra of Spitzer 24 μm Galaxies in the Cosmic Evolution Survey Field. II. Faint Infrared Sources in the zCOSMOS-Bright 10k Catalog K. I. Caputi, S. J. Lilly, H. Aussel, E. Le Floc'h, D. Sanders, C. Maier, D. Frayer, C. M. Carollo, T. Contini, J.-P. Kneib, O. Le Fèvre, V. Mainieri, A. Renzini, M. Scodeggio, N. Scoville, G. Zamorani, S. Bardelli, M. Bolzonella, A. Bongiorno, G. Coppa, O. Cucciati, S. de la Torre, L. de Ravel, P. Franzetti, B. Garilli, O. Ilbert, A. Iovino, P. Kampczyk, J. Kartaltepe, C. Knobel, K. Kovač, F. Lamareille, J.-F. Le Borgne, V. Le Brun, M. Mignoli, Y. Peng, E. Pérez-Montero, E. Ricciardelli, M. Salvato, J. Silverman, J. Surace, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, E. Zucca, U. Abbas, D. Bottini, P. Capak, A. Cappi, P. Cassata, A. Cimatti, M. Elvis, G. Hasinger, A. M. Koekemoer, A. Leauthaud, D. Maccagni, C. Marinoni, H. McCracken, P. Memeo, B. Meneux, P. Oesch, R. Pellò, C. Porciani, L. Pozzetti, R. Scaramella, C. Scarlata, D. Schiminovich, Y. Taniguchi, and M. Zamojski 2009 ApJ 707 1387-1403 doi: 10.1088/0004-637X/707/2/1387
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17134
Deposited By: Tony Diaz
Deposited On:11 Jan 2010 22:42
Last Modified:01 Mar 2017 20:02

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