期刊
ASTROPHYSICAL JOURNAL
卷 689, 期 2, 页码 775-781出版社
IOP PUBLISHING LTD
DOI: 10.1086/592592
关键词
accretion, accretion disks; galaxies: active; galaxies: individual (M87); galaxies: jets; stars: formation
资金
- CLAS
- University of Florida
- NSF CAREER [AST-0645412]
- Deutsche Forschungsgemeinschaft [BE2578]
- NSF [AST0406799, AST-0406823]
- NASA [ATP04-0000-0016 (NNG05GH61G)]
Supermassive black holes in giant elliptical galaxies are remarkably faint given their expected accretion rates. This motivates models of radiatively inefficient accretion due to either ion-electron thermal decoupling, generation of outflows that inhibit accretion, or settling of gas to a gravitationally unstable disk that forms stars in preference to feeding the black hole. The latter model predicts the presence of cold molecular gas in a thin disk around the black hole. Here we report Submillimeter Array observations of the nucleus of the giant elliptical galaxy M87 that probe 230 GHz continuum and CO (J = 2-1) line emission. Continuum emission is detected from the nucleus and several knots in the jet, including one that has been undergoing flaring behavior. We estimate a conservative upper limit on the mass of molecular gas within similar to 100 pc and +/- 400 km s(-1) line-of-sight velocity of the central black hole of similar to 8 x 10(6) M(circle dot), which includes an allowance for possible systematic errors associated with subtraction of the continuum. Ignoring such errors, we have a 3 sigma sensitivity to similar to 3 x 10(6) M(circle dot). In fact, the continuum-subtracted spectrum shows weak emission features extending up to 4 sigma above the rms dispersion of the line-free channels. These may be artifacts of the continuum subtraction process. Alternatively, if they are interpreted as CO emission, then the implied molecular gas mass is similar to 5 x 10(6) M(circle dot) spread out over a velocity range of 700 km s(-1). These constraints on molecular gas mass are close to the predictions of the model of self-gravitating, star-forming accretion disks fed by Bondi accretion (Tan & Blackman 2005).
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