GASKAP Pilot Survey Science. II. ASKAP Zoom Observations of Galactic 21 cm Absorption-猫眼课题宝

DOI：

10.3847/1538-4357/ac3a89

发表时间：

2021-11

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

J. Dickey;J. M. Dempsey;N. Pingel;N. McClure-Griffiths;K. Jameson;J. Dawson;H. D'enes;S. Clark;G. Joncas;D. Leahy;Min-Young Lee;M. Miville-Deschênes;S. Stanimirovi'c;C. Tremblay;J. V. van Loon

利用澳大利亚平方公里阵列探测器测量了连续背景源的21 cm吸收光谱，研究了远外盘和内银条末端附近经度340°的中性原子气体的冷相。在银河系内部，冷原子气体的尺度高度比太阳附近小，类似于分子气体和棒中的超薄恒星群体。在银河系外，冷原子气体与温暖的中性介质混合，冷部分与银河系半径大致保持不变。发射亮度温度与吸收的比率，即，1 − e −τ，对于银河系半径大于太阳圈半径两倍的速度，是大致恒定的。该比率具有约300 K的值，但这并不对应于气体中的物理温度。如果引起吸收的气体具有约100 K的动力学温度，如在太阳附近，则值300 K指示在该相中的气体质量的分数是总H i质量的三分之一。

Using the Australian Square Kilometre Array Pathfinder to measure 21 cm absorption spectra toward continuum background sources, we study the cool phase of the neutral atomic gas in the far outer disk, and in the inner Galaxy near the end of the Galactic bar at longitude 340°. In the inner Galaxy, the cool atomic gas has a smaller scale height than in the solar neighborhood, similar to the molecular gas and the super-thin stellar population in the bar. In the outer Galaxy, the cool atomic gas is mixed with the warm, neutral medium, with the cool fraction staying roughly constant with the Galactic radius. The ratio of the emission brightness temperature to the absorption, i.e., 1 − e −τ , is roughly constant for velocities corresponding to Galactic radius greater than about twice the solar circle radius. The ratio has a value of about 300 K, but this does not correspond to a physical temperature in the gas. If the gas causing the absorption has kinetic temperature of about 100 K, as in the solar neighborhood, then the value 300 K indicates that the fraction of the gas mass in this phase is one-third of the total H i mass.

GASKAP Pilot Survey Science. II. ASKAP Zoom Observations of Galactic 21 cm Absorption

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