Abstract
We study the evolution of the star formation rate (SFR) - stellar mass (M_star) 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 (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_star) 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_star>3.2 x 10^9 M_sun the SFR increases by a factor ~13 between z=0.4 and z=2.3. We extend this relation up to z=5, finding an additional increase in SFR by a factor 1.7 from z=2.3 to z=4.8 for masses M_star > 10^10 M_sun. We observe a turn-off in the SFR-M_star 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)^{Phi} with Phi=2-2.25 compared to the data which evolves more rapidly with Phi=2.8+-0.2. Above z~2, the reverse is happening with the data evolving more slowly with Phi=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_star 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 {abridge}
Highlights
Very Large Telescope, Paranal, Chile, under Large Program Star formation is a process fundamental to galaxy evolution. 185.A−0791.Stars form from gas made available from accretion processesArticle published by EDP Sciences A54, page 1 of 9A&A 581, A54 (2015)or that is recycled by exploding stars in their evolution cycles, different stellar populations with different histories are mixed in mergers, and they follow the dynamical evolution of galactic components forming bulges and discs leading to the spiral and elliptical galaxies observed today.It is well established that the star formation rate (SFR) history went through several phases (Madau & Dickinson 2014)
We study the evolution of the star formation rate (SFR) – stellar mass (M ) relation and specific star formation rate 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)
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
Summary
Very Large Telescope, Paranal, Chile, under Large Program Star formation is a process fundamental to galaxy evolution. Over the past few years, several apparently conflicting measurements show no evolution with redshift of sSFR (Stark et al 2009), a significant rise (Stark et al 2013; de Barros et al 2014; Salmon et al 2015), or even a decrease (Bouwens et al 2012). There are several difficulties linked to this process, including the impact on M and SFR of using different SFH, initial mass functions (IMF), or dust extinction laws These physical parameters depend in particular on the assumed SF histories and age priors as will be discussed in a forthcoming paper (Cassará et al, in prep.). Correcting for emission line contamination lowers M , and increases the sSFR, making significant differences in the measurement of the star formation main sequence at different redshifts. All magnitudes are given in the AB system, and we keep the AB notation apparent throughout the paper
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