The star formation rate in MaNGA AGN hosts is higher than in matched control galaxies

Abstract

We explore the relation between nuclear activity and star formation rate (SFR) in galaxies using data cubes from the MaNGA survey. We compare the SFR in 293 active galactic nuclei (AGN) host galaxies with that in 492 control galaxies, matched by host galaxy properties. Since gas ionization in AGN is not due to young stars, the SFR cannot be derived from gas emission. Instead, we use SFR from stellar population synthesis, considering components younger than 20 Myr. These results come from the so-called MEGACUBES. Comparing each AGN with its two matched controls, we find that AGN-host galaxies, on average, exhibit twice the SFR in their central regions compared to the control sample. The highest ratios are seen in the most luminous AGN and earliest-type AGN hosts, reaching approximately four times. We find a strong correlation between the black hole accretion rate (M˙ ) and nuclear SFR, supporting the interpretation that both are fuelled by the same gas reservoir. We further show that SFR presents negative gradients, steeper for AGN than for control galaxies. Finally, we obtain the global SFR integrated across the entire galaxy and find that AGN hosts lie slightly below the star formation main sequence (SFMS). However, we do not interpret this as evidence for AGN-driven quenching, since control galaxies fall even farther below the SFMS. Instead, our results suggest that ongoing nuclear activity is more often associated with enhanced star formation than with its suppression in host galaxies.