The evolving star formation rate: M⋆ relation and sSFR since z ≃ 5 from the VUDS spectroscopic survey

We study the evolution of the star formation rate (SFR) - stellar mass (MBlack 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 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(MBlack 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 MBlack star ≥ 3.2 × 109 M⊙ 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 MBlack star ≥ 1010 M⊙. We observe a turn-off in the SFR-MBlack 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)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 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 MBlack 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 including major and minor merging to further understand the co-evolution of the SFR and stellar mass growth