Name of the Speaker(s): Rohan Mahadevan
Institution:
Title of the communication: Scaling Laws for Advection Dominated Flows: Applications to
Low Luminosity Galactic Nuclei.
Preliminary abstract (12 lines max.):
We present analytical scaling laws for self--similar
advection dominated flows.
The spectra
from these systems range from 10$^{8}$ -- 10$^{20}$ Hz,
and are determined by considering cooling
of electrons through synchrotron,
bremsstrahlung, and Compton processes.
We show that the spectra can be quite accurately reproduced without
detailed numerical calculations, and that there is a strong
testable correlation between the radio and X-ray fluxes from these
systems. We describe how different
regions of the spectrum scale with the mass of the accreting
black hole, $M$, the accretion rate of the gas, $\dot{M}$,
and the equilibrium temperature of the electrons, $T_e$. We show
that the universal radio spectral index of 1/3 observed in
most elliptical galaxies (Slee et al. 1994) is a natural
consequence of self--absorbed synchrotron radiation from these
flows. We also
give expressions for the total luminosity of these
flows, and the critical accretion rate,
$\dot{M}_{\rm crit}$, above which the advection solutions
cease to exist. We find that for most cases of interest
the equilibrium
electron temperature is fairly insensitive to $M$, $\dot{M}$, and
parameters in the model. We apply these results to
low luminosity black holes in galactic nuclei. We show
that the problem posed by Fabian \& Canizares (1988)
of whether bright elliptical galaxies host
dead quasars is resolved,
as pointed out recently by Fabian \& Rees (1995),
by considering advection--dominated flows.