Molecular gas kinematics within the central 250 pc of the Milky Way
Molecular gas kinematics within the central 250 pc of the Milky Way
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DOI：
10.1093/mnras/stw121
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发表时间：
2016-04-11
影响因子：
4.8
通讯作者：
Zhang, Q.
中科院分区：
文献类型：
--
作者：
Henshaw, J. D.;Longmore, S. N.;Zhang, Q.
利用HNCO，N2 H+和HNC的谱线观测，我们研究了类似于银河系250 pc中心的致密气体的运动学。我们提出了SCOUSE（半自动多组分通用谱线拟合引擎），一个线拟合算法，旨在有效地和系统地分析大量的谱线数据。与不考虑复杂谱线轮廓的技术不同，SCOUSE精确地描述了中心分子区（CMZ）气体的{l，B，v（LsR）}分布，其在位置和速度上关于Sgr A* 不对称。速度弥散范围为2.6 km s（-1）< a < 53.1 km s（1）中位弥散为9.8 km s-1，换算为马赫数M-3D > 28。气体分布在几个“流”中，预计长度约为100-250 pc。我们链接的流到个人的云和子区域，包括Sgr C，20和50公里的S-1云，尘埃脊，和Sgr B2。壳状发射特征可以通过独立分子云在Sgr C中的投影和新发现的Sgr B2在{l，B，vi sR}空间中的锥形轮廓来解释。这些特征以前曾援引超新星驱动的壳层和云-云碰撞作为解释。相反，我们警告不要在速度综合排放图中进行结构识别。三个几何描述的三维结构的CMZ的调查：（i）两个螺旋臂;（ii）一个封闭的椭圆轨道;（iii）一个开放的流。虽然两个螺旋臂和一个开放的流定性地再现了气体分布，但最近的封闭椭圆轨道参数化并没有。最后，我们讨论了脉泽自行测量如何区分这些几何形状，并建议这项工作应集中在20 km s（-1）和50 km s（-1）的云和Sgr C。
Using spectral line observations of HNCO, N2H+, and HNC, we investigate the kinematics of dense gas in the central similar to 250 pc of the Galaxy. We present SCOUSE (Semi -automated multi-COmponent Universal Spectral-line fitting Engine), a line-fitting algorithm designed to analyse large volumes of spectral line data efficiently and systematically. Unlike techniques which do not account for complex line profiles, SCOUSE accurately describes the {l, b, v(LsR)} distribution of Central Molecular Zone (CMZ) gas, which is asymmetric about Sgr A* in both position and velocity. Velocity dispersions range from 2.6 km s(-1) < a < 53.1 km s (1) A median dispersion of 9.8 km s 1, translates to a Mach number, M-3D > 28. The gas is distributed throughout several 'streams', with projected lengths similar to 100-250 pc. We link the streams to individual clouds and sub-regions, including Sgr C, the 20 and 50 km s 1 clouds, the dust ridge, and Sgr B2. Shell-like emission features can be explained by the projection of independent molecular clouds in Sgr C and the newly identified conical profile of Sgr B2 in {l, b, vi sR} space. These features have previously invoked supernova-driven shells and cloud-cloud collisions as explanations. We instead caution against structure identification in velocity-integrated emission maps. Three geometries describing the 3D structure of the CMZ are investigated: (i) two spiral arms; (ii) a closed elliptical orbit; (iii) an open stream. While two spiral arms and an open stream qualitatively reproduce the gas distribution, the most recent parametrization of the closed elliptical orbit does not. Finally, we discuss how proper motion measurements of masers can distinguish between these geometries, and suggest that this effort should be focused on the 20 km s(-1) and 50 km s(-1) clouds and Sgr C.