An alternate approach to measure specific star formation rates at 2<z<7

TL;DR

This paper introduces a novel method to measure the specific star formation rates of massive galaxies at high redshift by analyzing the evolution of the galaxy stellar mass function, validated with simulations and applied to observational data.

Contribution

It presents a new approach that does not rely on direct SFR estimates, improving the measurement of sSFR at 2<z<7 using galaxy stellar mass functions.

Findings

sSFR scales as (1+z)^{1.1±0.2} at z>2

The method aligns with observations but conflicts with some simulation predictions

Future surveys will enhance the accuracy of this approach

Abstract

We trace the specific star formation rate (sSFR) of massive star-forming galaxies ($\gtrsim\!10^{10}\,\mathcal{M}_\odot$) from $z\sim2$ to 7. Our method is substantially different from previous analyses, as it does not rely on direct estimates of star formation rate, but on the differential evolution of the galaxy stellar mass function (SMF). We show the reliability of this approach by means of semi-analytical and hydrodynamical cosmological simulations. We then apply it to real data, using the SMFs derived in the COSMOS and CANDELS fields. We find that the sSFR is proportional to $(1+z)^{1.1\pm0.2}$ at $z>2$, in agreement with other observations but in tension with the steeper evolution predicted by simulations from $z\sim4$ to 2. We investigate the impact of several sources of observational bias, which however cannot account for this discrepancy. Although the SMF of high-redshift galaxies is still affected by significant errors, we show that future large-area surveys will substantially reduce them, making our method an effective tool to probe the massive end of the main sequence of star-forming galaxies.