The infrared-radio correlation of star-forming galaxies is strongly M∗-dependent but nearly redshift-invariant since z ∼4

Abstract

Over the past decade, several works have used the ratio between total (rest 8-1000 μm) infrared and radio (rest 1.4 GHz) luminosity in star-forming galaxies (qIR), often referred to as the infrared-radio correlation (IRRC), to calibrate the radio emission as a star formation rate (SFR) indicator. Previous studies constrained the evolution of qIR with redshift, finding a mild but significant decline that is yet to be understood. Here, for the first time, we calibrate qIR as a function of both stellar mass (M∗) and redshift, starting from an M∗-selected sample of > 400 000 star-forming galaxies in the COSMOS field, identified via (NUV - r)/(r - J) colours, at redshifts of 0.1 < z < 4.5. Within each (M∗,z) bin, we stacked the deepest available infrared/sub-mm and radio images. We fit the stacked IR spectral energy distributions with typical star-forming galaxy and IR-AGN templates. We then carefully removed the radio AGN candidates via a recursive approach. We find that the IRRC evolves primarily with M∗, with more massive galaxies displaying a systematically lower qIR.