The VLA-COSMOS 3 GHz Large Project: Cosmic star formation history since z ~ 5

¹ Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
e-mail: mlnovak@phy.hr
² INAF–Osservatorio Astronomico di Bologna, via Piero Gobetti 93/3, 40129 Bologna, Italy
³ Istituto di Radioastronomia di Bologna – INAF, via P. Gobetti, 101, 40129 Bologna, Italy
⁴ Spitzer Science Center, 314-6 Caltech, Pasadena, CA 91125, USA
⁵ National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA
⁶ Yale Center for Astronomy and Astrophysics, 260 Whitney Avenue, New Haven, CT 06520, USA
⁷ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁸ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, 13388 Marseille, France
⁹ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁰ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
¹¹ Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634-0978, USA
¹² Max-Planck-Institut für Extraterrestrische Physik (MPE), Postfach 1312, 85741 Garching, Germany
¹³ Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, UK
¹⁴ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received: 29 July 2016
Accepted: 15 January 2017

Abstract

We make use of the deep Karl G. Jansky Very Large Array (VLA) COSMOS radio observations at 3 GHz to infer radio luminosity functions of star-forming galaxies up to redshifts of z ~ 5 based on approximately 6000 detections with reliable optical counterparts. This is currently the largest radio-selected sample available out to z ~ 5 across an area of 2 square degrees with a sensitivity of rms ≈ 2.3 μJy beam^-1. By fixing the faint and bright end shape of the radio luminosity function to the local values, we find a strong redshift trend that can be fitted with a pure luminosity evolution L_{1.4 GHz} ∝ (1 + z)^{(3.16 ± 0.2)−(0.32 ± 0.07)z}. We estimate star formation rates (SFRs) from our radio luminosities using an infrared (IR)-radio correlation that is redshift dependent. By integrating the parametric fits of the evolved luminosity function we calculate the cosmic SFR density (SFRD) history since z ~ 5. Our data suggest that the SFRD history peaks between 2 < z < 3 and that the ultraluminous infrared galaxies (100 M_⊙ yr^-1 < SFR < 1000 M_⊙ yr^-1) contribute up to ~25% to the total SFRD in the same redshift range. Hyperluminous infrared galaxies (SFR > 1000 M_⊙ yr^-1) contribute an additional ≲2% in the entire observed redshift range. We find evidence of a potential underestimation of SFRD based on ultraviolet (UV) rest-frame observations of Lyman break galaxies at high redshifts (z ≳ 4) on the order of 15–20%, owing to appreciable star formation in highly dust-obscured galaxies, which might remain undetected in such UV observations.