Density profile of ambient circumnuclear medium in Seyfert 1 galaxies
  The shape of the ambient circumnuclear medium (ACM) density profile can probe
the history of accretion onto the central supermassive black hole in galaxies
and the circumnuclear environment. However, due to the limitation of the
instrument resolution, the density profiles of the ACM for most of galaxies
remain largely unknown. In this work, we propose a novel method to measure the
ACM density profile of active galactic nucleus (AGN) by the equilibrium between
the radiation pressure on the warm absorbers (WAs, a type of AGN outflows) and
the drag pressure from the ACM. We study the correlation between the outflow
velocity and ionization parameter of WAs in each of the five Seyfert 1 galaxies
(NGC 3227, NGC 3783, NGC 4051, NGC 4593, and NGC 5548), inferring that the
density profile of the ACM is between n\propto r^-1.7 and n \propto r^-2.15 (n
is number density and r is distance) from 0.01 pc to pc scales in these five
AGNs. Our results indicate that the ACM density profile in Seyfert 1 galaxies
is steeper than the prediction by the spherically symmetric Bondi accretion
model and the simulated results of the hot accretion flow, but more in line
with the prediction by the standard thin disk model.
