The M 31 double nucleus probed with OASIS and HST. A natural m=1 mode?
The M 31 double nucleus probed with OASIS and HST. A natural m=1 mode?
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用 OASIS 和 HST 探测 M 31 双核。
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
P. Martin
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作者：
R. Bacon;E. Emsellem;F. Combes;Y. Copin;G. Monnet;P. Martin
本文利用自适应光学辅助积分场光谱仪OASIS对m31双核在钙三重态周围的光谱域进行了观测，其空间分辨率优于0:00 5 FWHM。这些数据被用来推导在中央200的二维恒星运动学。在F300W， F555W和F814W波段重新访问了wfpc2 /HST图像，对核区进行了光度分解。我们还介绍了从档案中获得的STIS/HST运动学。中心区域的光度分布被很好地划分为凸起、包括P1和P2在内的核和所谓的UV峰的各自贡献。然后，我们使用OASIS运动学图显示，连接P1和P2（两个局部表面亮度最大值）的轴与运动长轴不重合，这也是核同卵体（不包括P1）的长轴。我们还证实，速度色散峰与UV峰相差0:2，假设这标志着超大质量黑洞的位置。然后将新减小的STIS/HST速度和弥散曲线与OASIS和其他已发表的运动学数据进行比较。我们发现与先前发表的数据有显著差异。然后建立简单的参数模型，以成功地协调所有可用的运动学。我们最终使用新体模拟来解释观测结果。m31的近开普勒核盘服从于自然的M = 1模式，具有非常慢的模式速度（MBH =7 10 7 M时为3 km s /pc），可以维持一千多次动力学时间。模型的形貌和运动学可以再现m31核盘光度和平均恒星速度，包括观测到的不对称性。它需要一个质量集中的中心和一个占其质量20%到40%的冷盘系统。当来自外部气态盘的星际云向中心坠落时，这种慢模式可能会被激发。由吸积气体形成的核盘可能是这类结构的前体，在星系的中心区域可能很常见。
We present observations with the adaptive optics assisted integral eld spectrograph OASIS of the M 31 double nucleus in the spectral domain around the Calcium triplet at a spatial resolution better than 0: 00 5 FWHM. These data are used to derive the two-dimensional stellar kinematics within the central 2 00 .A rchivalWFPC2/HST images in the F300W, F555W and F814W bands are revisited to perform a photometric decomposition of the nuclear region. We also present STIS/HST kinematics obtained from the archive. The luminosity distribution of the central region is well separated into the respective contributions of the bulge, the nucleus including P1 and P2, and the so-called UV peak. We then show, using the OASIS kinematical maps, that the axis joining P1 and P2, the two local surface brightness maxima, does not coincide with the kinematic major-axis, which is also the major-axis of the nuclear isophotes (excluding P1). We also conrm that the velocity dispersion peak is oset by0: 2f rom the UV peak, assumed to mark the location of the supermassive black hole. The newly reduced STIS/HST velocity and dispersion proles are then compared to OASIS and other published kinematics. We nd signicant osets with previously published data. Simple parametric models are then built to successfully reconcile all the available kinematics. We nally interpret the observations using newN-body simulations. The nearly Keplerian nuclear disk of M 31 is subject to a natural m = 1 mode, with a very slow pattern speed (3 km s 1 /pc for MBH =7 10 7 M), that can be maintained during more than a thousand dynamical times. The resulting morphology and kinematics of the mode can reproduce the M 31 nuclear-disk photometry and mean stellar velocity, including the observed asymmetries. It requires a central mass concentration and a cold disk system representing between 20 and 40% of its mass. Such a slow mode could be excited when interstellar clouds from the more external gaseous disk infall towards the centre. Nuclear disks formed from accreted gas are possible candidates for the precursors of these types of structures, and may be common in central regions of galaxies.