A two-fluid model for black-hole accretion flows: Particle acceleration,
  outflows, and TeV emission
  The multi-wavelength spectrum observed from M87 extends from radio
wavelengths up to TeV gamma-ray energies. The radio through GeV components have
been interpreted successfully using SSC models based on misaligned blazar jets,
but the origin of the intense TeV emission detected during flares in 2004,
2005, and 2010 remains puzzling. It has been previously suggested that the TeV
flares are produced when a relativistic proton jet originating in the core of
M87 collides with a molecular cloud (or stellar atmosphere) located less than
one parsec from the central black hole. We explore this scenario in detail here
using a self-consistent model for the acceleration of relativistic protons in a
shocked, two-fluid ADAF accretion disc. The relativistic protons accelerated in
the disc escape to power the observed jet outflows. The distribution function
for the jet protons is used to compute the TeV emission produced when the jet
collides with a cloud or stellar atmosphere. The simulated broadband radiation
spectrum includes radio, X-ray, and GeV components generated via synchrotron,
as well as TeV emission generated via the production and decay of muons,
positrons, and electrons. The self-consistency of the model is verified by
computing the relativistic particle pressure using the distribution function,
and comparing it with the relativistic particle pressure obtained from the
hydrodynamical model. We demonstrate that the model is able to reproduce the
multi-wavelength spectrum from M87 observed by VERITAS and HESS during the
high-energy flares in 2004, 2005, and 2010.
