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arXiv 1507.01945astro-ph.GA
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高分辨率的Galerkin探测Galerkin:z=0.4时与Milky Way类似物相关的同向旋转气体

Galaxies Probing Galaxies at High Resolution: Co-Rotating Gas Associated with a Milky Way Analog at z=0.4

Aleksandar M. Diamond-Stanic, Alison L. Coil, John Moustakas, Christy A. Tremonti, Paul H. Sell, Alexander J. Mendez, Ryan C. Hickox, Greg H. Rudnick

摘要:

我们目前的结果气体流动的晕的银河系类星系在z=0.413的基础上的高分辨率光谱的背景星系。这是第一次以高光谱分辨率对扩展背景源(即,星系而不是类星体)。利用前景星系的长缝光谱,我们观测到了圆自转速度v=270 km/s的空间扩展H α辐射。使用阶梯光谱的背景星系,我们检测到Mg II和Fe II的吸收线在碰撞参量rho=27千秒差距的蓝移从系统的意义上的前景星系的旋转。最强的吸收体EW(2796)= 0.90 A的柱密度(NH>10^19 cm-2)和视向速度色散(σ =17 km/s)的估计值与局部宇宙中扩展的H I盘的观测特性一致。我们对自转曲线的分析还表明,这个r=30 kpc的气体盘相对于恒星盘是翘曲的。此外,我们检测到两个弱的Mg II吸收晕的速度分散小(西格玛<10公里/秒)。虽然确切的几何形状尚不清楚,但其中一个组成部分与盘-晕界面附近的面外气体云一致,与盘共同旋转,另一个组成部分与类似于麦哲伦流的潮汐特征一致。考虑到背景源的扩展性质,我们可以对这些吸收体的云大小设置较低的限制(l>0.4 kpc)。我们讨论了这些结果的影响模型的几何形状和运动学的气体在环星系介质。

英文摘要:

We present results on gas flows in the halo of a Milky Way-like galaxy at z=0.413 based on high-resolution spectroscopy of a background galaxy. This is the first study of circumgalactic gas at high spectral resolution towards an extended background source (i.e., a galaxy rather than a quasar). Using longslit spectroscopy of the foreground galaxy, we observe spatially extended H alpha emission with circular rotation velocity v=270 km/s. Using echelle spectroscopy of the background galaxy, we detect Mg II and Fe II absorption lines at impact parameter rho=27 kpc that are blueshifted from systemic in the sense of the foreground galaxy's rotation. The strongest absorber EW(2796) = 0.90 A has an estimated column density (N_H>10^19 cm-2) and line-of-sight velocity dispersion (sigma=17 km/s) that are consistent with the observed properties of extended H I disks in the local universe. Our analysis of the rotation curve also suggests that this r=30 kpc gaseous disk is warped with respect to the stellar disk. In addition, we detect two weak Mg II absorbers in the halo with small velocity dispersions (sigma<10 km/s). While the exact geometry is unclear, one component is consistent with an extraplanar gas cloud near the disk-halo interface that is co-rotating with the disk, and the other is consistent with a tidal feature similar to the Magellanic Stream. We can place lower limits on the cloud sizes (l>0.4 kpc) for these absorbers given the extended nature of the background source. We discuss the implications of these results for models of the geometry and kinematics of gas in the circumgalactic medium.

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