Elbaz, D. and Blain, A. and Bock, J. and Chary, R.-R. and Cooray, A. and Dowell, C. D. and Levenson, L. and Lu, N. and Nguyen, H. T. and Schulz, B. and Shupe, D. L. and Vieira, J. and Xu, C. K. and Zemcov, M. (2010) Herschel unveils a puzzling uniformity of distant dusty galaxies. Astronomy and Astrophysics, 518 . Art. No. L29. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20101202-085141496
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The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved over the last 80% of the age of the Universe. We discuss possible consequences for the determination of starformation rates (SFR) and any evidence for a major change in their star-formation properties. We use Herschel deep extragalactic surveys from 100 to 500 μm to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). An extension to fainter luminosities is done by stacking images on 24 μm prior positions. We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used, e.g. at 24 μm, to identify “isolated” galaxies whose flux is not boosted by bright neighbors. Below z ~ 1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15 dex), therefore similar to z ~ 0 galaxies, over three decades in luminosity below the regime of ultra-luminous IR galaxies (ULIRGs, L_(IR) ≥ 10^(12) L_⊙). This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160 μm, 250 μm or 350 μm bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ~150 μm (rest-frame) before Herschel on those templates. We also note that the dust temperature of luminous IR galaxies (LIRGs, L_(IR) ≥ 10^(11) L_⊙) around z ~ 1 is mildly colder by 10–15% than their local analogs and up to 20% for ULIRGs at z ~ 1.6 (using a single modified blackbody-fit to the peak far-IR emission with an emissivity index of β = 1.5). Above z = 1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor coeval star formation at very high SFR and in conditions similar to purely star-forming galaxies.
|Additional Information:||© 2010 ESO. Received 31 March 2010, Accepted 23 April 2010, Published online 16 July 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. 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); 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. Padua (Italy); IAC (Spain); Stockholm Observatory (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).|
|Subject Keywords:||galaxies: evolution, galaxies: active, galaxies: starburst, infrared: galaxies|
|Official Citation:||Herschel unveils a puzzling uniformity of distant dusty galaxies D. Elbaz, H. S. Hwang, B. Magnelli, E. Daddi, H. Aussel, B. Altieri, A. Amblard, P. Andreani, V. Arumugam, R. Auld, T. Babbedge, S. Berta, A. Blain, J. Bock, A. Bongiovanni, A. Boselli, V. Buat, D. Burgarella, N. Castro-Rodriguez, A. Cava, J. Cepa, P. Chanial, R.-R. Chary, A. Cimatti, D. L. Clements, A. Conley, L. Conversi, A. Cooray, M. Dickinson, H. Dominguez, C. D. Dowell, J. S. Dunlop, E. Dwek, S. Eales, D. Farrah, N. Förster Schreiber, M. Fox, A. Franceschini, W. Gear, R. Genzel, J. Glenn, M. Griffin, C. Gruppioni, M. Halpern, E. Hatziminaoglou, E. Ibar, K. Isaak, R. J. Ivison, G. Lagache, D. Le Borgne, E. Le Floc'h, L. Levenson, N. Lu, D. Lutz, S. Madden, B. Maffei, G. Magdis, G. Mainetti, R. Maiolino, L. Marchetti, A. M. J. Mortier, H. T. Nguyen, R. Nordon, B. O'Halloran, K. Okumura, S. J. Oliver, A. Omont, M. J. Page, P. Panuzzo, A. Papageorgiou, C. P. Pearson, I. Perez Fournon, A. M. Pérez García, A. Poglitsch, M. Pohlen, P. Popesso, F. Pozzi, J. I. Rawlings, D. Rigopoulou, L. Riguccini, D. Rizzo, G. Rodighiero, I. G. Roseboom, M. Rowan-Robinson, A. Saintonge, M. Sanchez Portal, P. Santini, M. Sauvage, B. Schulz, D. Scott, N. Seymour, L. Shao, D. L. Shupe, A. J. Smith, J. A. Stevens, E. Sturm, M. Symeonidis, L. Tacconi, M. Trichas, K. E. Tugwell, M. Vaccari, I. Valtchanov, J. Vieira, L. Vigroux, L. Wang, R. Ward, G. Wright, C. K. Xu and M. Zemcov A&A 518 L29 (2010) DOI: 10.1051/0004-6361/201014687|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||02 Dec 2010 19:22|
|Last Modified:||26 Dec 2012 12:42|
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