半人马座A：氢原子的形态学和运动学
Centaurus A: morphology and kinematics of the atomic hydrogen
摘要：
我们提出了新的ATCA 21厘米线观测的中性氢在附近的无线电星系半人马座A。我们详细地成像（分辨率低至7 "，~100pc）HI沿尘埃带的分布。我们的数据有更好的速度分辨率和更好的灵敏度比以前的观测。HI的总延伸约为15kpc。这些数据，结合一个标题环模型的磁盘，允许得出结论，HI的运动学是一个定期旋转，高度扭曲的结构下降到核尺度。我们的模型的参数（特别是倾角）与以前提出的一些模型有些不同，但与最近从中央环中的恒星光中得出的结果一致。该模型也很好地描述了用斯皮策观测到的尘埃带的形态。没有迹象表明，在运动学存在的大规模异常可能与活动星系核的物质供应。大规模的径向运动确实存在，但这些运动只存在于较大的半径r> 6kpc）。这种未沉降的气体主要是尾/臂状结构的一部分。在这个结构中，气体相对规则的运动学表明，它正处于沉降到主盘的过程中。这种结构的存在进一步支持了Cen A中HI的合并/相互作用起源。根据结构和运动学，我们估计自合并事件以来的时间尺度为1.6 - 3.2 * 10 ^{8}年。不需要杆结构来描述HI的运动学。从大规模的HI结构和无线电结构的相对规律性的HI下降到sub-kpc区域的时间尺度的比较并不表明合并和射电活动的阶段之间的一一对应关系。有趣的是，外部区域的径向运动使得投影速度与规则轨道相比发生了红移。这意味着，我们先前发现并讨论过的蓝移吸收不能由投射到中心的大半径外移气体引起。因此，蓝移吸收的解释，连同至少一部分红移的核吸收，作为一个规则的内盘的证据，仍然成立。最后，我们还报告了两个未解决的云检测到5.2和11千秒差距（投影）从HI磁盘的发现。它们可能是带来HI气体的合并遗留物的另一个例子。
英文摘要：
We present new ATCA 21-cm line observations of the neutral hydrogen in the nearby radio galaxy Centaurus A. We image in detail (with a resolution down to 7", ~100pc) the distribution of HI along the dust lane. Our data have better velocity resolution and better sensitivity than previous observations. The HI extends for a total of ~15kpc. The data, combined with a titled-ring model of the disk, allow to conclude that the kinematics of the HI is that of a regularly rotating, highly warped structure down to the nuclear scale. The parameters (in particular the inclination) of our model are somewhat different from some of the previously proposed models but consistent with what was recently derived from stellar light in a central ring. The model nicely describes also the morphology of the dust lane as observed with Spitzer. There are no indications that large-scale anomalies in the kinematics exist that could be related to supplying material for the AGN. Large-scale radial motions do exist, but these are only present at larger radii r>6kpc). This unsettled gas is mainly part of a tail/arm like structure. The relatively regular kinematics of the gas in this structure suggests that it is in the process of settling down into the main disk. The presence of this structure further supports the merger/interaction origin of the HI in Cen A. From the structure and kinematics we estimate a timescale of 1.6-3.2*10^{8}yr since the merging event. No bar structure is needed to describe the kinematics of the HI. The comparison of the timescale derived from the large-scale HI structure and those of the radio structure together with the relative regularity of the HI down to the sub-kpc regions does not suggest a one-to-one correspondence between the merger and the phase of radio activity. Interestingly, the radial motions of the outer regions are such that the projected velocities are redshifted compared to the regular orbits. This means that the blueshifted absorption discovered earlier and discussed in our previous paper cannot be caused by out-moving gas at large radius projected onto the centre. Therefore, the interpretation of the blueshifted absorption, together with at least a fraction of the redshifted nuclear absorption, as evidence for a regular inner disk, still holds. Finally, we also report the discovery of two unresolved clouds detected at 5.2 and 11kpc away (in projection) from the HI disk. They are likely an other example of left-over of the merger that brought the HI gas.
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