Gas infall towards Sgr A* from the clumpy circumnuclear disk
Gas infall towards Sgr A* from the clumpy circumnuclear disk
复制标题
气体从块状核周盘向 Sgr A* 流入
DOI：
10.1088/0004-637x/695/2/1477
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Paul T. P. Ho
中科院分区：
文献类型：
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作者：
M. Montero;Robeson M. Herrnstein;Paul T. P. Ho
我们展示了在银河系中心首次使用亚毫米阵列 (SMA) 进行的大规模马赛克。我们制作了一个 25 点马赛克，覆盖 Sgr A* 周围约 2' x 2' 的区域。我们检测到两种高密度分子示踪剂 HCN(4-3) 和 CS(7-6) 的发射，后者此前从未在该地区报道过。数据的角分辨率为4.6"x 3.1"，HCN(4-3)的光谱窗口覆盖范围为-180 km/s至1490 km/s，CS(7-6)的光谱窗口覆盖范围为-1605 km/s至129 km/s。两种分子示踪剂均沿核周盘（CND）呈现非常块状的分布，并且在CND的南部检测到较高的信噪比，而在北部则较弱。假设这些团块与银河系中心的距离与其投影距离一样近，那么它们的密度仍然足以在超大质量黑洞产生的潮汐剪切作用下保持重力稳定。因此，CND是一种非瞬态结构。两种示踪剂的几何分布表明 CND 的南部部分比北部部分更密集。另外，通过比较HCN(4-3)和HCN(1-0)结果可以看出，CND的北部和南部具有不同的激发水平，南部比北部温暖。最后，我们将我们的结果与 NH3 检测获得的结果进行比较，NH3 追踪了 CND 内腔中检测到的较温暖且密度较低的物质。我们建议我们正在探测CND的一部分变得不稳定并接近银河系动力中心的原点，可能受到南方流光的影响并在向内移动的过程中被加热。
We present the first large-scale mosaic performed with the Submillimeter Array (SMA) in the Galactic center. We have produced a 25-pointing mosaic, covering a ~2' x 2' area around Sgr A*. We have detected emission from two high-density molecular tracers, HCN(4-3) and CS(7-6), the latter never before reported in this region. The data have an angular resolution of 4.6"x 3.1", and the spectral window coverage is from -180 km/s to 1490 km/s for HCN(4-3) and from -1605 km/s to 129 km/s for CS(7-6). Both molecular tracers present a very clumpy distribution along the circumnuclear disk (CND), and are detected with a high signal-to-noise ratio in the southern part of the CND, while they are weaker towards the northern part. Assuming that the clumps are as close to the Galactic center as their projected distances, they are still dense enough to be gravitationally stable against the tidal shear produced by the supermassive black hole. Therefore, the CND is a non-transient structure. This geometrical distribution of both tracers suggests that the southern part of the CND is denser than the northern part. Also, by comparing the HCN(4-3) results with HCN(1-0) results we can see that the northern and the southern parts of the CND have different excitation levels, with the southern part warmer than the northern. Finally, we compare our results with those obtained with the detection of NH3, which traces the warmer and less dense material detected in the inner cavity of the CND. We suggest that we are detecting the origin point where a portion of the CND becomes destabilized and approaches the dynamical center of the Milky Way, possibly being impacted by the southern streamer and heated on its way inwards.