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arXiv 0707.4176astro-ph
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作为超大质量黑洞供给通道的核螺旋:星系NGC 6951的情况

Nuclear spirals as feeding channels to the Supermassive Black Hole: the case of the galaxy NGC 6951

Thaisa Storchi-Bergmann, Oli L. Dors, Rogemar A. Riffel, Kambiz Fathi, David J. Axon, Andrew Robinson, Alessandro Marconi, Goran Ostlin

摘要:

我们报告的气体流运动沿核旋臂的星系NGC 6951的LINER核的发现。这些观测是使用北双子座望远镜上的GMOS积分场摄谱仪获得的,它们绘制出了银河系内部7 x5弧秒^[2]的31条发射线H α [NII]6584和[SII] 6717的通量分布图和气体运动学图。这个区域包括一个半径为500 pc的环绕核的恒星形成环,环内的核螺旋和LINER核。电离气体的运动学是由旋转主导的,但是减去旋转指数盘的运动学模型揭示了核环内的圆形旋转的偏差,这可以归因于(1)沿着核螺旋臂的流动运动和(2)似乎与核喷流有关的双极流出。根据观测到的气流速度和旋臂的几何形状,我们估计电离气体的质量流入速率为3 × 10 ^(-4)Msun/yr,这与NGC 6951 LINER核所需的吸积速率相当。我们小组在以前的一篇论文中已经报道了另一个具有LINER核的星系- NGC 1097 -的核的类似流动运动。总的来说,这些结果支持这样一种假设,即核螺旋是物质从银河系尺度转移到核区域以供给超大质量黑洞的通道。

英文摘要:

We report the discovery of gas streaming motions along nuclear spiral arms towards the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Halpha, [NII]6584 and [SII]6717,31 emission lines of the inner 7x5 arcsec^2 of the galaxy. This region includes a circumnuclear star-forming ring with radius 500pc, a nuclear spiral inside the ring and the LINER nucleus. The kinematics of the ionized gas is dominated by rotation, but subtraction of a kinematic model of a rotating exponential disk reveals deviations from circular rotation within the nuclear ring which can be attributed to (1) streaming motions along the nuclear spiral arms and (2) a bipolar outflow which seems to be associated to a nuclear jet. On the basis of the observed streaming velocities and geometry of the spiral arms we estimate a mass inflow rate of ionized gas of 3x10^(-4) Msun/yr, which is of the order of the accretion rate necessary to power the LINER nucleus of NGC 6951. Similar streaming motions towards the nucleus of another galaxy with LINER nucleus -- NGC 1097 -- have been reported by our group in a previous paper. Taken together, these results support a scenario in which nuclear spirals are channels through which matter is transferred from galactic scales to the nuclear region to feed the supermassive black hole.

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