Kinematics of Circumgalactic Gas: Feeding Galaxies and Feedback
Kinematics of Circumgalactic Gas: Feeding Galaxies and Feedback
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DOI：
10.3847/1538-4357/ab18ac
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发表时间：
2019-01
期刊：
影响因子：
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通讯作者：
C. Martin;S. Ho;G. Kacprzak;C. Churchill
中科院分区：
文献类型：
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作者：
C. Martin;S. Ho;G. Kacprzak;C. Churchill
我们展示了 50 对红移 z ≈ 0.2 恒星形成星系和背景类星体的观测结果。这些视线探测环河介质（CGM）到维里半径的一半，我们描述了相对于银盘定义的参考系的环河气体运动学。我们检测了 Mg ii 吸收中的晕气体，测量了相对于每个星系的等效宽度加权多普勒频移，并发现 CGM 具有与银盘对齐的角动量分量。在任何冲击参数下，在长轴 45° 范围内均未检测到 CGM 的净反向旋转。环河气体的速度偏移与盘平面内大约 70 kpc 半径的预计旋转速度相关。我们证实了先前的说法，即 Mg ii 吸收在银河系短轴附近变得更强，并且我们表明等效宽度与吸收的速度范围相关。我们无法直接测量沿视线的任何吸收体的位置，但我们探索了这样的假设：各个速度分量可能与在圆盘平面中绕轨道运行或在锥形流出物中径向向外流动的气体相关。我们得出的结论是，离心力部分支持了低电离气体，而星系外流在运动学上扰乱了 CGM，产生了过量的吸收。我们的结果坚决排除了缺乏旋转的内部 CGM 的模式，并表明角动量和银河风应该包含在任何可行的低红移 CGM 模型中。
We present observations of 50 pairs of redshift z ≈ 0.2 star-forming galaxies and background quasars. These sightlines probe the circumgalactic medium (CGM) out to half the virial radius, and we describe the circumgalactic gas kinematics relative to the reference frame defined by the galactic disks. We detect halo gas in Mg ii absorption, measure the equivalent-width-weighted Doppler shifts relative to each galaxy, and find that the CGM has a component of angular momentum that is aligned with the galactic disk. No net counter-rotation of the CGM is detected within 45° of the major axis at any impact parameter. The velocity offset of the circumgalactic gas correlates with the projected rotation speed in the disk plane out to disk radii of roughly 70 kpc. We confirm previous claims that the Mg ii absorption becomes stronger near the galactic minor axis, and we show that the equivalent width correlates with the velocity range of the absorption. We cannot directly measure the location of any absorber along the sightline, but we explore the hypothesis that individual velocity components can be associated with gas orbiting in the disk plane or flowing radially outward in a conical outflow. We conclude that centrifugal forces partially support the low-ionization gas and galactic outflows kinematically disturb the CGM producing excess absorption. Our results firmly rule out schema for the inner CGM that lack rotation and suggest that angular momentum as well as galactic winds should be included in any viable model for the low-redshift CGM.