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GOODS-Herschel: a population of 24 μm dropout sources at z<2

Magdis, G. E. and Armus, L. (2011) GOODS-Herschel: a population of 24 μm dropout sources at z<2. Astronomy and Astrophysics, 534 . A15. ISSN 0004-6361.

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Using extremely deep PACS 100- and 160 μm Herschel data from the GOODS-Herschel program, we identify 21 infrared bright galaxies previously missed in the deepest 24   μm surveys performed by Spitzer/MIPS. These MIPS dropouts are predominantly found in two redshift bins, centred at z ~ 0.4 and ~1.3. Their S_(100)/S_(24) flux density ratios are similar to those of local (ultra-) luminous infrared galaxies (LIRGs and ULIRGs), whose silicate absorption features at 18 μm (at z ~ 0.4) and 9.7 μm (at z ~ 1.3) are shifted into the 24 μm MIPS band at these redshifts. The high-z sub-sample consists of 11 infrared luminous sources, accounting for ~2% of the whole GOODS-Herschel sample and putting strong upper limits on the fraction of LIRGs/ULIRGs at 1.0 < z < 1.7 that are missed by the 24 μm surveys. We find that a S_(100)/S_(24) > 43 colour cut selects galaxies with a redshift distribution similar to that of the MIPS dropouts and when combined with a second colour cut, S_(16)/S_8 > 4, isolates sources at 1.0 < z < 1.7. We show that these sources have elevated specific star formation rates (sSFR) compared to main sequence galaxies at these redshifts and are likely to be compact starbursts with moderate/strong 9.7 μm silicate absorption features in their mid-IR spectra. Herschel data reveal that their infrared luminosities extrapolated from the 24 μm flux density are underestimated, on average, by a factor of ~3. These silicate break galaxies account for 16% (8%) of the ULIRG (LIRG) population in the GOODS fields, indicating a lower limit in their space density of 2.0 × 10^(-5) Mpc^(-3). Finally, we provide estimates of the fraction of z < 2 MIPS dropout sources as a function of the 24-, 100-, 160-, 250- and 350   μm sensitivity limits, and conclude that previous predictions of a population of silicate break galaxies missed by the major 24   μm extragalactic surveys have beenoverestimated.

Item Type:Article
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Magdis, G. E.0000-0002-4872-2294
Armus, L.0000-0003-3498-2973
Additional Information:© 2011 ESO. Article published by EDP Sciences. Received 7 July 2011; Accepted 3 August 2011. Published online 22 September 2011. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. G.E.M. acknowledge the support of the Centre National de la Research Scientifique (CNRS) and the University of Oxford. H.S.H. and D.E. acknowledge the support of the Centre National d’Études Spatiales (CNES) PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAFIFSI/OAA/OAP/OAT, LENS, SISSA (Italy) and IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padova (Italy); IAC (Spain); SNSB (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); Stockholm Observatory (Sweden); STFC (UK); and NASA (USA). This work is based [in part] on observations made with Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Centre National de la Research Scientifique (CNRS)UNSPECIFIED
University of OxfordUNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Comisión Interministerial de Ciencia y Tecnología (CICYT)UNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
National Astronomical Observatories, Chinese Academy of Sciences (NAOC)UNSPECIFIED
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Stockholm ObservatoryUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Ministerio de Ciencia Y Tecnologia (MCYT)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:galaxies: active; galaxies: evolution; galaxies: formation; galaxies: groups: general; infrared: galaxies
Record Number:CaltechAUTHORS:20111128-115241856
Persistent URL:
Official Citation:GOODS-Herschel: a population of 24 μm dropout sources at z < 2 G. E. Magdis, D. Elbaz, M. Dickinson, H. S. Hwang, V. Charmandaris, L. Armus, E. Daddi, E. Le Floc’h, H. Aussel, H. Dannerbauer, D. Rigopoulou, V. Buat, G. Morrison, J. Mullaney, D. Lutz, D. Scott, D. Coia, A. Pope, M. Pannella, B. Altieri, D. Burgarella, M. Bethermin, K. Dasyra, J. Kartaltepe, R. Leiton, B. Magnelli, P. Popesso and I. Valtchanov A&A 534 A15 (2011) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27978
Deposited By: Jason Perez
Deposited On:28 Nov 2011 21:08
Last Modified:24 Feb 2020 10:30

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