Kinematics of the Circumgalactic Medium of a z = 0.77 Galaxy from Mg ii Tomography
Kinematics of the Circumgalactic Medium of a z = 0.77 Galaxy from Mg ii Tomography
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DOI：
10.3847/1538-4357/abfa11
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发表时间：
2020-05
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通讯作者：
K. Mortensen;Keerthi Vasan G. C.;T. Jones;C. Faucher-Giguère;R. Sanders;R. Ellis;N. Leethochawalit;D. Stark
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作者：
K. Mortensen;Keerthi Vasan G. C.;T. Jones;C. Faucher-Giguère;R. Sanders;R. Ellis;N. Leethochawalit;D. Stark
星系演化被认为在很大程度上是由星系和环星系介质之间的气体流动推动的，环星系介质是从每个星系延伸到≳100kpc的富含金属的气体的光晕。研究CGM的空间结构为理解这些气体流动机制提供了希望；然而，使用背景类星体视线的常见方法提供的空间信息最少。最近的工作显示了扩展的背景源的实用性，例如巨大的引力透镜弧光。利用CSWA38透镜系统的背景透镜弧线，在分辨率约为15kPc2的条件下，连续探测了恒星形成星系在z=0.77时(恒星质量≈109.7 M⊙，恒星形成率≈10 M⊙yr−1)、碰撞参数D≃5-30kpc时镁II吸收的空间和运动分布。我们的结果给出了一种各向异性的光学厚度介质，其吸收强度随着碰撞参数的增加而减小，这与对类星体和其他引力弧的统计一致。此外，与镁II气体中相对较高的速度弥散(典型的σ≈50 KM S−1)相比，我们发现通常较低的视线速度。虽然星系本身在下桶谱上表现出明显的外流(镁II速度高达∼500公里S−1)，但外流分量是次要的，只有在背景弧探测到的较大撞击参数下才能弱检测到。我们的结果提供了主要由分散体支撑的、富金属气体通过CGM循环的证据。
Galaxy evolution is thought to be driven in large part by the flow of gas between galaxies and the circumgalactic medium (CGM), a halo of metal-enriched gas extending out to ≳100 kpc from each galaxy. Studying the spatial structure of the CGM holds promise for understanding these gas flow mechanisms; however, the common method of using background quasar sight lines provides minimal spatial information. Recent works have shown the utility of extended background sources such as giant gravitationally lensed arcs. Using background lensed arcs from the CSWA 38 lens system, we continuously probed, at a resolution element of about 15 kpc2, the spatial and kinematic distribution of Mg ii absorption in a star-forming galaxy at z = 0.77 (stellar mass ≈109.7 M ⊙, star formation rate ≈10 M ⊙ yr−1) at impact parameters D ≃ 5–30 kpc. Our results present an anisotropic, optically thick medium whose absorption strength decreases with increasing impact parameter, in agreement with the statistics toward quasars and other gravitational arcs. Furthermore, we find generally low line-of-sight velocities in comparison to the relatively high velocity dispersion in the Mg ii gas (with typical σ ≈ 50 km s−1). While the galaxy itself exhibits a clear outflow (with Mg ii velocities up to ∼500 km s−1) in the down-the-barrel spectrum, the outflow component is subdominant and only weakly detected at larger impact parameters probed by the background arcs. Our results provide evidence of mainly dispersion-supported, metal-enriched gas recycling through the CGM.