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