What is the accretion rate in NGC 4258?

被引:92
作者
Gammie, CF
Narayan, R
Blandford, R
机构
[1] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
[2] CALTECH, Pasadena, CA 91125 USA
[3] Isaac Newton Inst, Cambridge CB3 0EH, England
关键词
accretion; accretion disks; galaxies : individual (NGC 4258); galaxies : nuclei; masers; X-rays : galaxies;
D O I
10.1086/307089
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We estimate the accretion rate (M) over dot onto the black hole in the nucleus of NGC 4258. The result is model dependent. We find that a thin disk that is flat out to greater than or equal to 2 x 10(3) GM/c(2) (M = black hole mass) and that has inclination equal to that of the masing disk must have (M) over dot similar or equal to 0.01 M-. yr(-1) for consistency with near-infrared data. A thin disk that is warped at similar to 10(3) GM/c(2) requires (M) over dot greater than or similar to 1.5 x 10(-4) M-. yr(-1) for consistency with near-infrared data. Reasonable warp models and the near-infrared data are not consistent with (M) over dot as low as the 7 x 10(-5) alpha M-. yr(-1) proposed by Neufeld & Maloney. An advection-dominated flow model combined with the X-ray data implies (M) over dot similar or equal to 0.01 M-. yr(-1). Consistency with a tight 22 GHz upper limit on the flux from the central source requires a transition radius of similar to(10-100)GM/c(2), although the 22 GHz upper limit may be relaxed by appeal to free-free absorption. Physical conditions in the observed VLBI jet features can also be related to conditions in the inner accretion how. We conclude with a list of observations that might further constrain (M) over dot.
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页码:177 / 186
页数:10
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