Astronomy & Astrophysics manuscript no. sfr-history c ESO 2017 March 31, 2017 The VLA-COSMOS 3 GHz Large Project: Cosmic star formation history since z ∼ 5 M. Novak1, V. Smolciˇ c´1, J. Delhaize1, I. Delvecchio1, G. Zamorani2, N. Baran1, M. Bondi3, P. Capak4, C. L. Carilli5, P. Ciliegi2, F. Civano6, 7, O. Ilbert8, A. Karim9, C. Laigle10, O. Le Fèvre8, S. Marchesi11, H. McCracken10, O. Miettinen1, M. Salvato12, M. Sargent13, E. Schinnerer14, L. Tasca8 1 Department of Physics, Faculty of Science, University of Zagreb, Bijenickaˇ cesta 32, 10000 Zagreb, Croatia 2 INAF - Osservatorio Astronomico di Bologna, Via Piero Gobetti 93/3, I-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, P.O. 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, D-53121 Bonn, Germany 10 Institut d’Astrophysique de Paris, UMR7095 CNRS, Universit e Pierre et Marie Curie, 98 bis 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, D-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, D-69117 Heidelberg, Germany Received ; accepted 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 6 000 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 (3.16±0.2)−(0.32±0.07)z trend that can be fitted with a pure luminosity evolution L1.4 GHz ∝ (1 + 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 −1 −1 peaks between 2 < z < 3 and that the ultraluminous infrared galaxies (ULIRGs; 100 M⊙ yr < SFR < 1000 M⊙ yr ) contribute up −1 to ∼25% to the total SFRD in the same redshift range. Hyperluminous infrared galaxies (HyLIRGs; SFR > 1000 M⊙ yr ) 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 (LBGs) 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. Key words. galaxies: evolution – galaxies: star formation – cosmology: observations – radio continuum: galaxies 1. Introduction Although the wealth of observations has increased dramat- ically in the last decade, we still do not understand the core mechanism that governs star formation rate (SFR) histories of arXiv:1703.09724v2 [astro-ph.GA] 30 Mar 2017 One of the best methods to follow the buildup of stellar individual galaxies. This is because of our inability to actu- mass through cosmic times relies on inferring the cosmic ally follow these galaxies throughout their evolution. We ob- star formation rate density (SFRD) history (for a review, see serve galaxy populations at different cosmic epochs and try to Madau & Dickinson 2014). A consensus is achieved regard- link them in a consistent way. A picture has emerged from ing recent history, where an exponential decline in SFRD by this method in which blue star-forming (SF) galaxies evolve one order of magnitude from redshift z ∼ 2 to the present into red quiescent galaxies through ways of quenching, such day is inferred (e.g., Madau et al. 1996; Haarsma et al. 2000; as rapid gas reservoir depletion after major merger interactions Hopkins et al. 2006). On the other hand, with an increasing num- or active galactic nuclei (AGN) feedback (e.g., Bell et al. 2004; ber of ultra-deep surveys the detection threshold is continually Schawinski et al. 2014). On the other hand, Bouché et al. (2010) being pushed to higher redshifts (up to z ∼ 10) slowly reach- presented a quenching-freemodel based on the cosmological de- ing the epoch of reionization (e.g., Bouwens et al. 2014a, 2015). crease of accretion rates with time, which is able to reproduce The light of the early galaxies is a major factor in the process of the observed SFRD. Another model has also been proposed that reionization (e.g., Bouwens 2016), and so accurate SFRD mea- uses simple mathematical lognormal forms for SFRD and indi- surements are needed to better understand this epoch. Article number, page 1 of 18 A&A proofs: manuscript no. sfr-history vidual SFR history to reproduce a wide range of observed re- to probe this population at early cosmic epochs. However, deep lations (e.g., Gladders et al. 2013; Abramson et al. 2016). When surveys have to sacrifice area in order to be feasible, which the SFRD history is estimated with sufficient precision it can be makes them more susceptible to cosmic over- and underdensi- used to further constrain semianalytical models of galaxy evo- ties. This cosmic variance can have a strong redshift-dependent lution, thereby deepening our understanding of the underlying impact to any counting statistic employed (e.g., Moster et al. physics. 2011). Different SFR tracers can be used over the full electro- The Cosmological Evolution Survey (COSMOS) 2 deg2 magnetic spectrum, each with its own benefits and shortcom- field (Scoville et al. 2007) is therefore well suited for our stud- ings (e.g., Kennicutt 1998). The most direct tracer measures ies due to its large area, which should minimize cosmic vari- ultraviolet (UV) light from young massive stars and can be ance, and excellent multiwavelength coverage, which allows linked with the amount of star formation in the galaxy (e.g., for a precise photometric redshift determination. With the new Buat et al. 1989). The rest-frame UV emission is redshifted to Karl G. Jansky Very Large Array (VLA) observations obtained optical and infrared (IR) wavelengths for the most distant galax- for the VLA-COSMOS 3 GHz Large Project (Smolciˇ c´ et al. ies; this enables the usage of very sensitive instruments, such as 2017b), the deepest radio survey to date given the area, we can the Hubble Space Telescope (HST), to probe this epoch (e.g., probe the dust-unbiased SFRD up to redshift of z ∼ 5 with Finkelstein et al. 2015). Currently, the SFRD in the earliest cos- ∼6000 detections of SF galaxies. Our radio data best traces 10 mic times (age of the universe less than 1 Gyr) is constrained high-mass (M⋆ > 10 M⊙) and highly SF galaxies (SFR −1 almost exclusively with these kinds of observations (see also > 100 M⊙ yr ), which would also be classified as ultralumi- 12 Behroozi et al. 2013). However, when measuring the rest-frame nous infrared galaxies (ULIRGs; LTIR, 8-1000 µm > 10 L⊙, see UV emission one must correct for dust extinction, which dras- Sanders & Mirabel 1996). At high redshift, we can also con- tically diminishes the UV light. Well-constrained attenuation strain even brighter hyperluminous infrared galaxy (HyLIRG; 13 curves are needed to correct for this effect (e.g., Bouwens et al. LTIR, 8-1000 µm > 10 L⊙) populations, which have SFRs that are −1 2009). higher than 1000 M⊙ yr . To derive the total SFRD history of When dust grains absorb UV light they re-emit it at IR the entire radio population in the entire observed redshift range wavelengths. Therefore, far-IR and sub-mm traces SFR best we must rely on extrapolations to lower luminosities below the when the dust content is high, yielding a large optical depth. sensitivity limit. These observations can suffer from poor resolution and source The paper is organized as follows. In Sect. 2 we briefly de- blending, although this was mitigated with observations with scribe the data and selection methods used, which by itself is the Herschel Space Observatory. Current observations allow a topic of an accompanying paper (Smolciˇ c´ et al. 2017a). We IR surveys to constrain the dust content and SFRs up to red- present methods of constructing luminosity functions and mod- shift z < 4 (e.g., Caputi et al. 2005; Rodighiero et al. 2010; eling their evolution through cosmic time and our results in Reddy et al. 2012; Gruppioni et al. 2013). Ultraviolet and IR Sect. 3. The calibration used to to derive SFR from radio lu- observations can be combined to obtain a more robust hybrid minosities is explained in Sect. 4 along with the cosmic SFRD SFR estimator (e.g., Wuyts et al. 2011; Boquien et al. 2016). history estimated from our data. We compare our results to the With the high-resolution sub-mm window opened by the At- literature in Sect. 5. Discussion of possible systematics are given acama Large Millimeter/submillimeter Array (ALMA), these in Sect.