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An Accretion-Disk Model with Cooling through Molecular Lines

机译:通过分子线冷却的吸积盘模型

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Weinvestigatedanaccretion-diskmodelwithline-coolingofH$$_2$$OandCO.Theabundancesofmoleculeswerecalculatednumericallybythechemicalreactionnetwork,alongwiththestructureofthedisk.Itwasfoundthat,whenthemodelisappliedtotheKepleriandiskobservedinthenucleusofNGC4258,thetemperatureis$$T$$$$simeq$$400a€“500K,thenumberdensityofmolecularhydrogenis$$n$$(H$$_2$$)$$simeq$$10$$^{7}$$a€“10$$^{9}$$cm$$^{-3}$$,andthefractionalabundanceofH$$_2$$Oamountsto10$$^{-3}$$inthemaseremittingregionforthemass-accretionrate$$dot{M}$$$$simeq$$10$$^{-6}$$a€“10$$^{-7}M_{odot}$$yr$$^{-1}$$andtheviscosityparameter$$alpha$$$$=$$0.1.Intheouterregion,thediskisbothgeometricallyandopticallythin,thedrifttimeisatmost1Gyr,self-gravityofthediskcanbeneglected,andirradiationfromtheinnerdiskisofalsoanegligibleeffect.TheToomre$$Q$$parameterisgreaterthanunity,leadingthedisktobegravitationallystable.Itwasalsofoundthatthesephysicalcircumstancescannotbeachievedintheopticallythickmodelcooledbyblackbodyradiation.
机译:我们研究了一种在线冷却H $$ _ 2 $$ O和CO的吸积盘模型。通过化学反应网络以及盘的结构对分子的丰度进行了数字计算。发现当模型将凯特勒斯圆盘上的水分子($$$ T $$ T = $ K $$ T $($$$$ T $$$$$)时,模型将K $$$($$ T $)的温度计算为$ C $ 258。 $$ simeq $$ 10 $$ ^ {7} $$ a€“ 10 $$ ^ {9} $$ cm $$ ^ {-3} $$,以及H $$ _ 2 $$ O的分数丰度到10 $$ ^ {-3}积聚区域中的$$,积聚速率为$$ dot {M} $$$ simeq $$ 10 $$ ^ {-6-6 $$ a€” 10 $$ ^ {-7} M_ {odot} $$ yr $$ ^ {- 1} $$ andtheviscosityparameter $$阿尔法$$$$ = $$ 0.1.Intheouterregion,thediskisbothgeometricallyandopticallythin,thedrifttimeisatmost1Gyr,自我gravityofthediskcanbeneglected,andirradiationfromtheinnerdiskisofalsoanegligibleeffect.TheToomre $$ Q $$ parameterisgreaterthanunity,leadingthedisktobegravitationallystable.Itwasalsofoundthatthesephysicalcircumstancescannotbeachievedintheopticallythickmodelcooledbyblackbodyradiation。

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