Do Circumnuclear Dense Gas Disks Drive Mass Accretion onto Supermassive
  Black Holes?
  We present a positive correlation between the mass of dense molecular gas
($M_{\rm dense}$) of $\sim 100$ pc scale circumnuclear disks (CNDs) and the
black hole mass accretion rate ($\dot{M}_{\rm BH}$) in total 10 Seyfert
galaxies, based on data compiled from the literature and an archive (median
aperture $\theta_{\rm med}$ = 220 pc). A typical $M_{\rm dense}$ of CNDs is
10$^{7-8}$ $M_\odot$, estimated from the luminosity of the dense gas tracer,
the HCN($1-0$) emission line. Because dense molecular gas is the site of star
formation, this correlation is virtually equivalent to the one between nuclear
star formation rate and $\dot{M}_{\rm BH}$ revealed previously. Moreover, the
$M_{\rm dense}-\dot{M}_{\rm BH}$ correlation was tighter for CND-scale gas than
for the gas on kpc or larger scales. This indicates that CNDs likely play an
important role in fueling black holes, whereas $>$kpc scale gas does not. To
demonstrate a possible approach for studying the CND-scale accretion process
with the Atacama Large Millimeter/submillimeter Array (ALMA), we used a mass
accretion model where angular momentum loss due to supernova explosions is
vital. Based on the model prediction, we suggest that only the partial fraction
of the mass accreted from the CND ($\dot{M}_{\rm acc}$) is consumed as
$\dot{M}_{\rm BH}$. However, $\dot{M}_{\rm acc}$ agrees well with the total
nuclear mass flow rate (i.e., $\dot{M}_{\rm BH}$ + outflow rate). Although
these results are still tentative with large uncertainties, they support the
view that star formation in CNDs can drive mass accretion onto supermassive
black holes in Seyfert galaxies.
