Joseph A. Munoz, Steven R. Furlanetto
We develop a radiation pressure-balanced model for the interstellar medium of
high-redshift galaxies that describes many facets of galaxy formation at z>~6,
including star formation rates and distributions and gas accretion onto central
black holes. We first show that the vertical gravitational force in the disk of
such a model is dominated by the disk self-gravity but that both radiation
pressure on dust grains and turbulent pressure from dense clumps and disk
instabilities are negligible compared with the radiation pressure of starlight
on gas. Constraining our model to reproduce the UV luminosity function of
Lyman-break galaxies (LBGs), we limit the available parameter-space to wind
mass-loading factors 1--4 times the canonical value for momentum-driven winds.
We then focus our study by exploring the effects of different angular momentum
transport mechanisms in the galactic disk and find that viscosity driven by
gravitational torques, such as from linear spiral waves or non-linear orbit
crossings, can build up black hole masses by z=6 consistent with canonical
M-sigma relations with a duty cycle of unity, while infall mediated by a local
viscosity such as in an alpha-disk results in negligible BH accretion. Both
gravitational torque models produce X-ray emission from active galactic nuclei
in high redshift LBGs in excess of the estimated contribution from high-mass
X-ray binaries and consistent with a recent analysis of deep Chandra
observations by Cowie et al. We find that future observations with larger
sample sizes may be able to distinguish between these different angular
momentum transport mechanisms.
View original:
http://arxiv.org/abs/1201.1300
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