The multiwavelength spectrum of NGC 3115: Hot accretion flow properties
  NGC 3115 is the nearest galaxy hosting a billion solar mass black hole and is
also a low-luminosity active galactic nucleus (LLAGN). X-ray observations of
this LLAGN are able to spatially resolve the hot gas within the sphere of
gravitational influence of the supermassive black hole. These observations make
NGC 3115 an important testbed for black hole accretion theory in galactic
nuclei since they constrain the outer boundary conditions of the hot accretion
flow. We present a compilation of the multiwavelength spectral energy
distribution (SED) of the nucleus of NGC 3115 from radio to X-rays. We report
the results from modeling the observed SED with radiatively inefficient
accretion flow (RIAF) models. The radio emission can be well-explained by
synchrotron emission from the RIAF without the need for contribution from a
relativistic jet. We obtain a tight constraint on the RIAF density profile,
$\rho(r) \propto r^{-0.73_{-0.02} ^{+0.01}}$, implying that mass-loss through
subrelativistic outflows from the RIAF is significant. The lower frequency
radio observation requires the synchrotron emission from a nonthermal electron
population in the RIAF, similarly to Sgr A*.
