The evolving SFR-M_star relation and sSFR since z~5 from the VUDS spectroscopic survey

TL;DR

This study tracks the evolution of the star formation rate-stellar mass relation and specific star formation rate of galaxies from redshift 0.4 to 5.5 using the VUDS survey, revealing complex growth patterns and quenching mechanisms.

Contribution

It provides the first continuous analysis of SFR-M_star and sSFR over such a large redshift range from a single spectroscopic sample, highlighting deviations from existing models.

Findings

SFR increases by a factor of ~13 from z=0.4 to 2.3 for M_star>3.2x10^9 M_sun

Additional SFR increase by a factor of 1.7 from z=2.3 to 4.8 for M_star>10^10 M_sun

sSFR evolution is not well matched by current gas accretion or hydrodynamical models

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}