气体向M81核的流动
Gas Streaming Motions towards the Nucleus of M81
摘要：
我们利用双子座北望远镜上的GMOS积分场摄谱仪以10 pc的空间分辨率获得的光谱，给出了Liner/Seyfert 1星系M81内部120 × 250 pc ^2的恒星和气体运动学。恒星的速度场显示出圆旋转，但观察到的偏差接近短轴，这可以归因于恒星的运动可能与核棒。根据M_BH-sigma关系，球核的恒星速度色散为162 km/s，导致黑洞的质量为M_BH= 5.5 × 10^7 M_sun。气体的运动学主要是非圆运动，减去恒星速度场后，发现星系远端的蓝移约为-100 km/s，而近端则有少量的红移。如果气体在平面内，这些特征可以解释为流向中心。根据观测到的流动速度和几何形状，我们估计电离气体的质量流入速率约为4.0 × 10 ^-3 M太阳/年，这与为M81 LINER核提供能量所需的吸积速率相当。我们还应用了主成分分析（PCA）的技术，我们的数据，这揭示了存在一个旋转的核气体盘内的~ 50 pc的核和紧凑的流出，近似垂直于磁盘。PCA结合观测到的气体速度场表明，核盘是由星系平面内循环的气体供给的。外流的存在是由一个紧凑的喷流在无线电观测中看到在一个类似的方向，以及由增强的[OI] \Halpha线比，可能是由于由无线电喷流的环核气体的冲击激发。通过这些观测，我们解决了供给-通过核盘和观测到的气体流入，以及反馈-通过流出，围绕M81的核。
英文摘要：
We present stellar and gaseous kinematics of the inner 120x250pc^2 of the Liner/Seyfert 1 galaxy M81, from optical spectra obtained with the GMOS integral field spectrograph on the Gemini North telescope at a spatial resolution of 10pc. The stellar velocity field shows circular rotation but deviations are observed close to the minor axis which can be attributed to stellar motions possibly associated to a nuclear bar. The stellar velocity dispersion of the bulge is 162km/s leading to a black hole mass of M_BH=5.5x10^7M_sun based on the M_BH-sigma relationship. The gas kinematics is dominated by non-circular motions and the subtraction of the stellar velocity field reveals blueshifts of ~-100km/s on the far side of the galaxy and a few redshifts on the near side. These characteristics can be interpreted in terms of streaming towards the center if the gas is in the plane. On the basis of the observed velocities and geometry of the flow, we estimate a mass inflow rate in ionized gas of ~4.0x10^-3M_sun/year, which is of the order of the accretion rate necessary to power the LINER nucleus of M81. We have also applied the technique of Principal Component Analysis (PCA) to our data, which reveals the presence of a rotating nuclear gas disk within ~50pc from the nucleus and a compact outflow, approximately perpendicular to the disk. The PCA combined with the observed gas velocity field shows that the nuclear disk is being fed by gas circulating in the galaxy plane. The presence of the outflow is supported by a compact jet seen in radio observations at a similar orientation, as well as by an enhancement of the [OI]\Halpha line ratio, probably resulting from shock excitation of the circumnuclear gas by the radio jet. With these observations we are thus resolving both the feeding -- via the nuclear disk and observed gas inflow, and the feedback -- via the outflow, around the nucleus of M81.
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