Letter to the Editor

PEP: First Herschel probe of dusty galaxy evolution up to z ~ 3 ^*,**

¹ INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: carlotta.gruppioni@oabo.inaf.it
² Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ ESO, Karl-Schwarzschild-Strasse 2, 85748, Garching, Germany
⁴ INAF - Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁵ Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 3, 35122 Padova, Italy
⁶ ESAC, Villafranca del Castillo, 28692 Madrid, Spain
⁷ CEA-Saclay, Service d'Astrophysique, 91191 Gif-sur-Yvette, France
⁸ Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, 85741 Garching, Germany
⁹ Instituto de Astrofísica de Canarias, 38205, La Laguna, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, Spain
¹¹ Department of Astronomy, 610 Space Sciences Building, Cornell University, Ithaca, NY 14853, USA
¹² INAF - IFSI, Via Fosso del Cavaliere 100, 00133 Roma, Italy
¹³ INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy

Received: 31 March 2010
Accepted: 28 April 2010

Abstract

Aims. We exploit the deepest existing far-infrared (FIR) data obtained so far by Herschel at 100 and 160 μm in the GOODS-N, as part of the PACS evolutionary probe (PEP) survey, to derive for the first time the evolution of the rest-frame 60-μm, 90-μm, and total IR luminosity functions (LFs) of galaxies and AGNs from z = 0 to unprecedented high redshifts (z ~ 2–3).

Methods. The PEP LFs were computed using the 1/V_max method. The FIR sources were classified by means of a detailed broad-band SED-fitting analysis and spectral characterisation. Based on the best-fit model results, k-correction and total IR (8–1000 μm) luminosity were obtained for each source. LFs (monochromatic and total) were then derived for various IR populations separately in different redshift bins and compared to backward evolution model predictions.

Results. We detect strong evolution in the LF to at least z ~ 2. Objects with SEDs similar to local spiral galaxies are the major contributors to the star formation density (SFD) at z ≲ 0.3, then, as redshift increases, moderate SF galaxies – most likely containing a low-luminosity AGN – start dominating up to z 1.5. At z ≳ 1.5 the SFD is dominated by the contributions of starburst galaxies. In agreement with previous findings, the comoving IR LD derived from our data evolves approximately as (1 + z)^3.8±0.3 up to z ~ 1, there being some evidence of flattening up to z ~ 2.