The evolution of the star formation activity per halo mass up to redshift  ~1.6 as seen by Herschel^⋆

¹ Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, 85741 Garching, Germany
e-mail: popesso@mpe.mpg.de
² INAF/Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy
³ Dipartimento di Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁴ INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁵ Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁶ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/Service d’Astrophysique, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁷ Herschel Science Centre, European Space Astronomy Centre, ESA, Villanueva de la Cañada, 28691 Madrid, Spain
⁸ ESO, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁹ Spitzer Science Center, 314-6 Caltech, 1201 E. California Blvd. Pasadena, 91125, USA
¹⁰ Department of Astronomy, 249-17 Caltech, 1201 E. California Blvd. Pasadena, 91125, USA
¹¹ Departamento de Astrofísica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹² National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
¹³ NASA Herschel Science Center, Caltech 100-22, Pasadena, CA 91125, USA
¹⁴ Institute for Astronomy 2680, Woodlawn Drive Honolulu, HI 96822-1897, USA
¹⁵ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
¹⁶ George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA

Received: 30 August 2011
Accepted: 13 October 2011

Abstract

Aims. Star formation in massive galaxies is quenched at some point during hierarchical mass assembly. To understand where and when the quenching processes takes place, we study the evolution of the total star formation rate per unit total halo mass (Σ(SFR)/M) in three different mass scales: low mass halos (field galaxies), groups, and clusters, up to a redshift z ≈ 1.6.

Methods. We use deep far-infrared PACS data at 100 and 160 μm to accurately estimate the total star formation rate of the luminous infrared galaxy population of 9 clusters with mass  ~10¹⁵ M_⊙, and 9 groups/poor clusters with mass  ~5 × 10¹³ M_⊙. Estimates of the field Σ(SFR)/M are derived from the literature, by dividing the star formation rate density by the mean comoving matter density of the universe.

Results. The field Σ(SFR)/M increases with redshift up to z ~ 1 and it is constant thereafter. The evolution of the Σ(SFR)/M – z relation in galaxy systems is much faster than in the field. Up to redshift z ~ 0.2, the field has a higher Σ(SFR)/M than galaxy groups and galaxy clusters. At higher redshifts, galaxy groups and the field have similar Σ(SFR)/M, while massive clusters have significantly lower Σ(SFR)/M than both groups and the field. There is a hint of a reversal of the SFR activity vs. environment at z ~ 1.6, where the group Σ(SFR)/M lies above the field Σ(SFR)/M − z relation. We discuss possible interpretations of our results in terms of the processes of downsizing, and star-formation quenching.