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GOODS–Herschel: an infrared main sequence for star-forming galaxies

Elbaz, D. and Armus, L. and Mazzarella, J. and Chary, R.-R. and Murphy, E. and Huynh, M. and Teplitz, H. (2011) GOODS–Herschel: an infrared main sequence for star-forming galaxies. Astronomy and Astrophysics, 533 . Art. No. A119. ISSN 0004-6361.

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We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3–500 μm spectral energy distributions (SEDs) of galaxies at 0 < z < 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes. We find that the ratio of total IR luminosity to rest-frame 8 μm luminosity, IR8 (≡ L_(IR)^(tot)/L_8), follows a Gaussian distribution centered on IR8 = 4 (σ = 1.6) and defines an IR main sequence for star-forming galaxies independent of redshift and luminosity. Outliers from this main sequence produce a tail skewed toward higher values of IR8. This minority population (<20%) is shown to consist of starbursts with compact projected star formation densities. IR8 can be used to separate galaxies with normal and extended modes of star formation from compact starbursts with high–IR8, high projected IR surface brightness (Σ_(IR)  >  3 × 10^(10) L_⊙ kpc^(-2)) and a high specific star formation rate (i.e., starbursts). The rest-frame, UV-2700 Å size of these distant starbursts is typically half that of main sequence galaxies, supporting the correlation between star formation density and starburst activity that is measured for the local sample. Locally, luminous and ultraluminous IR galaxies, (U)LIRGs (L_(IR)^(tot)≥ 10^(11) L_☉), are systematically in the starburst mode, whereas most distant (U)LIRGs form stars in the “normal” main sequence mode. This confusion between two modes of star formation is the cause of the so-called “mid-IR excess” population of galaxies found at z > 1.5 by previous studies. Main sequence galaxies have strong polycyclic aromatic hydrocarbon (PAH) emission line features, a broad far-IR bump resulting from a combination of dust temperatures (T_(dust) ~ 15–50 K), and an effective T_(dust)  ~ 31 K, as derived from the peak wavelength of their infrared SED. Galaxies in the starburst regime instead exhibit weak PAH equivalent widths and a sharper far-IR bump with an effective T_(dust)~ 40 K. Finally, we present evidence that the mid-to-far IR emission of X-ray active galactic nuclei (AGN) is predominantly produced by star formation and that candidate dusty AGNs with a power-law emission in the mid-IR systematically occur in compact, dusty starbursts. After correcting for the effect of starbursts on IR8, we identify new candidates for extremely obscured AGNs.

Item Type:Article
Related URLs:
URLURL TypeDescription
Elbaz, D.0000-0002-7631-647X
Armus, L.0000-0003-3498-2973
Mazzarella, J.0000-0002-8204-8619
Chary, R.-R.0000-0001-7583-0621
Murphy, E.0000-0001-7089-7325
Teplitz, H.0000-0002-7064-5424
Additional Information:© 2011 ESO. Received 11 May 2011. Accepted 3 August 2011. Published online 13 September 2011. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. We wish to thank R.Gobat for generating the three color images of the GOODS fields and our referee Kai Noeske for his constructive comments that helped improving the paper. D. Elbaz and H. S. Hwang thank the Centre National d’Études Spatiales (CNES) for their support. D. Elbaz wishes to thank the French National Agency for Research (ANR) for their support (ANR-09-BLAN-0224). V.C. would like to acknowledge partial support from the EU ToK grant 39965 and FP7-REGPOT 206469. Support for this work was also provided by NASA through an award issued by JPL/Caltech. 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).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Agence Nationale pour la Recherche (ANR)ANR-09-BLAN-0224
European Research Council (ERC)39965
European Research Council (ERC)206469
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
European Space Agency (ESA) PROgramme for the Development of scientific EXperiments (PRODEX) (Belgium)UNSPECIFIED
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Deutschen Zentrums für Luft- und Raumfahrt (DLR)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
National Astronomical Observatories, Chinese Academy of Sciences (NAOC)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Ministerio de Ciencia e Innovación (MCINN)UNSPECIFIED
Stockholm ObservatoryUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:galaxies: active; infrared: galaxies; galaxies: evolution; galaxies: starburst
Record Number:CaltechAUTHORS:20111024-095346758
Persistent URL:
Official Citation:GOODS–Herschel: an infrared main sequence for star-forming galaxies D. Elbaz, M. Dickinson, H. S. Hwang, T. Díaz-Santos, G. Magdis, B. Magnelli, D. Le Borgne, F. Galliano, M. Pannella, P. Chanial, L. Armus, V. Charmandaris, E. Daddi, H. Aussel, P. Popesso, J. Kartaltepe, B. Altieri, I. Valtchanov, D. Coia, H. Dannerbauer, K. Dasyra, R. Leiton, J. Mazzarella, D. M. Alexander, V. Buat, D. Burgarella, R.-R. Chary, R. Gilli, R. J. Ivison, S. Juneau, E. Le Floc’h, D. Lutz, G. E. Morrison, J. R. Mullaney, E. Murphy, A. Pope, D. Scott, M. Brodwin, D. Calzetti, C. Cesarsky, S. Charlot, H. Dole, P. Eisenhardt, H. C. Ferguson, N. Förster Schreiber, D. Frayer, M. Giavalisco, M. Huynh, A. M. Koekemoer, C. Papovich, N. Reddy, C. Surace, H. Teplitz, M. S. Yun and G. Wilson A&A 533 A119 (2011) DOI: 10.1051/0004-6361/201117239
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27373
Deposited By: Ruth Sustaita
Deposited On:24 Oct 2011 18:11
Last Modified:03 Oct 2019 03:23

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