Star formation history of ≤ z ≤ mass-selected galaxies in the ELAIS-N1 Field

Abstract

ABSTRACT We measure the specific star formation rates (sSFRs) of K-band selected galaxies from the European Large Area ISO Survey North 1 by stacking Giant Metrewave Radio Telescope data at 610 MHz. We identify a sample of star-forming galaxies (SFGs), spanning ${0.1\le \, {z}\, \le \, 1.5}$ and $\rm {10^{8.5}\lt \, {{\mathit{ M}}_{\star }}/{{M}_{\odot }}\lt 10^{12.4}}$, using a combination of multiwavelength diagnostics obtained from the deep LOw Frequency ARray Two-metre Sky Survey multiwavelength catalogue. We measure the flux densities in the radio map and estimate the radio SFR in order to probe the nature of the galaxies below the noise and confusion limits. The massive galaxies in our sample have the lowest sSFRs, which is in agreement with previous studies. For the different populations, we show that the sSFR–mass relation steepens with redshift, with an average slope of $\rm {\langle \beta _{All} \rangle \, =\, -0.49\pm 0.01}$ for the whole sample, and $\rm {\langle \beta _{SFG} \rangle \, =\, -0.42\pm 0.02}$ for the SFGs. Our results indicate that galaxy populations undergo ’downsizing’, whereby most massive galaxies form their stars earlier and more rapidly than low-mass galaxies. Both populations show a strong decrease in their sSFR towards the present epoch. The sSFR evolution with redshift is best described by a power law ${(1\, +\, {z})^{n}}$, where $\rm {\langle {\mathit{ n}}_{ALL}\rangle \sim 4.94\pm 0.53}$ for all galaxies and $\rm {\langle {\mathit{ n}}_{SFG}\rangle \sim 3.51\pm 0.52}$ for SFGs. Comparing our measured sSFRs to results from literature, we find a general agreement in the sSFR–M⋆ plane.