New techniques to investigate the AGN-SF connection with integral field spectroscopy

Abstract Understanding the connection between active galactic nuclei and star-formation (the AGN-SF connection) is one of the longest standing problems in modern astrophysics. In the age of large integral field unit (IFU) surveys, studies of the AGN-SF connection greatly benefit from spatially resolving AGN and SF contributions to study the two processes independently. Using IFU data for 54 local active galaxies from the S7 sample, we present a new method to separate emission from AGN activity and SF using mixing sequences observed in the [NII] $\unicode{x03BB}$ 6 584 Å/ ${\mathrm{H}}\unicode{x03B1}$ vs. [OIII] $\unicode{x03BB}$ 5 007 Å/ ${\mathrm{H}}\unicode{x03B2}$ Baldwin–Phillips–Terlevich diagram. We use the new decomposition method to calculate the ${\mathrm{H}}\unicode{x03B1}$ star-formation rate and AGN [OIII] luminosity for the galaxies. Our new method is robust to outliers in the line ratio distribution and can be applied to large galaxy samples with little manual intervention. We infer star-formation histories using pPXF, conducting detailed recovery tests to determine the quantities that can be considered robust. We test the correlation between the AGN Eddington ratio, using the proxy $L\mathrm{[O{III}]}/\sigma_*^4$ , and star-formation properties. We find a moderately strong correlation between the Eddington ratio and the star-formation rate. We also observe marginally significant correlations between the AGN Eddington ratio and the light-weighted stellar age under 100 Myr. Our results point to higher AGN accretion being associated with young nuclear star-formation under 100 Myr, consistent with timelines presented in previous studies. The correlations found in this paper are relatively weak; extending our methods to larger samples, including radio-quiet galaxies, will help better constrain the physical mechanisms and timescales of the AGN–SF connection.