Volume 581, September 2015
|Number of page(s)||9|
|Published online||01 September 2015|
The evolving star formation rate: M⋆ relation and sSFR since z ≃ 5 from the VUDS spectroscopic survey⋆
1 Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
2 Geneva Observatory, University of Geneva, Ch. des Maillettes 51, 1290 Versoix, Switzerland
3 Institut de Recherche en Astrophysique et Planétologie – IRAP, CNRS, Université de Toulouse, UPS-OMP, 14 avenue E. Belin, 31400 Toulouse, France
4 University of Bologna, Department of Physics and Astronomy (DIFA), V.le Berti Pichat, 6/2, 40127 Bologna, Italy
5 Instituto de Fisica y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, 1111 Gran Bretaña, Playa Ancha Valparaíso, Chile
6 INAF–IASF Milano, via Bassini 15, 20133 Milano, Italy
7 INAF–Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
8 University of Bologna, Department of Physics and Astronomy (DIFA), V.le Berti Pichat, 6/2, 40127 Bologna, Italy
9 Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA
10 Department of Astronomy, University of Geneva, Ch. d’Écogia 16, 1290 Versoix, Switzerland
11 INAF–IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
12 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125, USA
13 Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
14 Institut de Recherche en Astrophysique et Planétologie – IRAP, CNRS, Université de Toulouse, UPS-OMP, 14 avenue E. Belin, 31400 Toulouse, France
15 SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, UK
16 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
17 Centro de Estudios de Física del Cosmos de Aragón, 44001 Teruel, Spain
18 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching bei München, Germany
19 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249–17, Pasadena, CA 91125, USA
20 Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, 790-8577 Matsuyama, Japan
Received: 20 November 2014
Accepted: 20 June 2015
We study the evolution of the star formation rate (SFR) – stellar mass (M⋆) relation and specific star formation rate (sSFR) of star-forming galaxies (SFGs) since a redshift z ≃ 5.5 using 2435 (4531) galaxies with highly reliable spectroscopic redshifts in the VIMOS Ultra-Deep Survey (VUDS). It is the first time that these relations can be followed over such a large redshift range from a single homogeneously selected sample of galaxies with spectroscopic redshifts. The log (SFR) − log (M⋆) relation for SFGs remains roughly linear all the way up to z = 5, but the SFR steadily increases at fixed mass with increasing redshift. We find that for stellar masses M⋆ ≥ 3.2 × 109M⊙ the SFR increases by a factor of ~13 between z = 0.4 and z = 2.3. Weextend this relation up to z = 5, finding an additional increase in SFR by a factor of 1.7 from z = 2.3 to z = 4.8 for masses M⋆ ≥ 1010M⊙. We observe a turn-off in the SFR–M⋆ relation at the highest mass end up to a redshift z ~ 3.5. We interpret this turn-off as the signature of a strong on-going quenching mechanism and rapid mass growth. The sSFR increases strongly up to z ~ 2, but it grows much less rapidly in 2 <z< 5. We find that the shape of the sSFR evolution is not well reproduced by cold gas accretion-driven models or the latest hydrodynamical models. Below z ~ 2 these models have a flatter evolution (1 + z)Φ with Φ = 2 − 2.25 compared to the data which evolves more rapidly with Φ = 2.8 ± 0.2. Above z ~ 2, the reverse is happening with the data evolving more slowly with Φ = 1.2 ± 0.1. The observed sSFR evolution over a large redshift range 0 <z< 5 and our finding of a non-linear main sequence at high mass both indicate that the evolution of SFR and M⋆ is not solely driven by gas accretion. The results presented in this paper emphasize the need to invoke a more complex mix of physical processes including major and minor merging to further understand the co-evolution of the SFR and stellar mass growth.
Key words: galaxies: evolution / galaxies: star formation / galaxies: formation / galaxies: high-redshift
© ESO, 2015
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