2015A&A...581A..54T

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_*≥3.2x10⁹M_☉ the SFR increases by a factor of ∼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 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.