THE RELATIONSHIP BETWEEN BLACK HOLE GROWTH AND STAR FORMATION IN SEYFERT GALAXIES

Abstract

We present estimates of black hole accretion rates and nuclear, extended, and\ntotal star-formation rates for a complete sample of Seyfert galaxies. Using\ndata from the Spitzer Space Telescope, we measure the active galactic nucleus\n(AGN) luminosity using the [O IV] 25.89 micron emission line and the\nstar-forming luminosity using the 11.3 micron aromatic feature and extended 24\nmicron continuum emission. We find that black hole growth is strongly\ncorrelated with nuclear (r<1 kpc) star formation, but only weakly correlated\nwith extended (r>1 kpc) star formation in the host galaxy. In particular, the\nnuclear star-formation rate (SFR) traced by the 11.3 micron aromatic feature\nfollows a relationship with the black hole accretion rate (BHAR) of the form\nSFR\\proptoBHAR^0.8, with an observed scatter of 0.5 dex. This SFR-BHAR\nrelationship persists when additional star formation in physically matched r=1\nkpc apertures is included, taking the form SFR\\proptoBHAR^0.6. However, the\nrelationship becomes almost indiscernible when total SFRs are considered. This\nsuggests a physical connection between the gas on sub-kpc and sub-pc scales in\nlocal Seyfert galaxies that is not related to external processes in the host\ngalaxy. It also suggests that the observed scaling between star formation and\nblack hole growth for samples of AGNs will depend on whether the star formation\nis dominated by a nuclear or extended component. We estimate the integrated\nblack hole and bulge growth that occurs in these galaxies and find that an AGN\nduty cycle of 5-10% would maintain the ratio between black hole and bulge\nmasses seen in the local universe.\n