Advection-dominated accretion, jets and the spectral energy distribution
  of LINERs
  Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN
population in the present-day universe and they trace low-level accreting
supermassive black holes. The observational properties of LLAGNs suggest that
their central engines are intrinsically different from those of more luminous
AGNs. It has been suggested that accretion in LLAGNs occurs via an
advection-dominated accretion flow (ADAF) associated with strong jets. In order
to probe the accretion physics in LLAGNs as a class, we model the
multiwavelength spectral energy distributions (SEDs) of 24 LINERs (taken from a
recent compilation by Eracleous et al.) with a coupled accretion-jet model. The
accretion flow is modeled as an inner ADAF outside of which there is a
truncated standard thin disk. These SEDs include radio, near-IR to near-UV HST
data, and Chandra X-ray data. We find that the radio emission is severely
underpredicted by ADAF models but can be explained by the relativistic jet. The
origin of the X-ray radiation in most sources can be explained by three
distinct scenarios: the X-rays can be dominated by emission from the ADAF, the
jet, or from both components contributing at similar levels. From the model
fits, we estimate important parameters of the central engine of LINERs, such as
the mass accretion rate -- relevant for studies of the feeding of AGNs -- and
the mass-loss rate in the jet and the jet power -- relevant for studies of the
kinetic feedback from jets.
