Chandra Survey of Nearby Galaxies: Testing the Accretion Model for
  Low-luminosity AGNs
  From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we
find that for low-luminosity AGNs (LLAGNs), either the intrinsic absorption
column density, or the fraction of absorbed AGNs, positively scales with the
Eddington ratio for $L_{\rm bol}/L_{\rm Edd} \lesssim 10^{-2}$. Such a
behavior, along with the softness of the X-ray spectrum at low luminosities, is
in good agreement with the picture that they are powered by hot accretion flows
surrounding supermassive black holes. Numerical simulations find that outflows
are inevitable with hot accretion flows, and the outflow rate is correlated
with the innermost accretion rate in the low-luminosity regime. This agrees
well with our results, suggesting that the X-ray absorption originates from or
is associated with the outflow material. Gas and dust on larger scales may also
produce the observed correlation. Future correlation analysis may help
differentiate the two scenarios.
