Hydrodynamical Accretion Onto Sgr A* From, Distributed Point Sources

Robert F. Coker(1,3) and Fulvio Melia(1,2,4)

(1)Physics Department, The University of Arizona, Tucson, AZ 85721
(2) Steward Observatory, The University of Arizona, Tucson, AZ 85721
(3) NASA GSRP Fellow
(4) Presidential Young Investigator

Paper: accepted by ApJL

Weblink: http://www.physics.arizona.edu/~rfc/ptsrc.ps.Z

EPrint Server: astro-ph/9708089


Abstract:

Spectral and kinematic studies suggest that the nonthermal radio source Sgr A*, located at the center of the Milky Way, is a supermassive compact object with a mass ~ 2-3*10^6\msun. Winds from nearby stars, located ~ 0.06 pc to the east of Sgr A*, should, in the absence of any outflow from the putative black hole itself, be accreting onto this object. We report the results of the first 3D Bondi-Hoyle hydrodynamical numerical simulations of this process under the assumption that the Galactic center wind is generated by several different point sources (here assumed to be 10 pseudo-randomly placed stars). Our results show that the accretion rate onto the central object can be higher than in the case of a uniform flow since wind-wind shocks dissipate some of the bulk kinetic energy and lead to a higher capture rate for the gas. However, even for this highly non-uniform medium, most of the accreting gas carries with it a relatively low level of specific angular momentum, though large transient fluctuations can occur. Additionally, the post-bow-shock focusing of the gas can be substantially different than that for a uniform flow, but it depends strongly on the stellar spatial distribution. We discuss how this affects the morphology of the gas in the inner 0.15 pc of the Galaxy and the consequences for accretion disk models of Sgr A*.


Preprints available from the authors at rfc@physics.arizona.edu , or the raw TeX (no figures) if you click here.

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