The QuaStar Survey: Detecting Hidden Low-velocity Gas in the Milky Way’s Circumgalactic Medium
The QuaStar Survey: Detecting Hidden Low-velocity Gas in the Milky Way’s Circumgalactic Medium
复制标题
DOI：
10.3847/1538-4357/abeb6b
复制
发表时间：
2020-10
期刊：
影响因子：
--
通讯作者：
H. Bish;J. Werk;J. Peek;Yonggang Zheng;M. Putman
中科院分区：
文献类型：
--
作者：
H. Bish;J. Werk;J. Peek;Yonggang Zheng;M. Putman
从我们位于银河系星际介质中的位置来看，我们探测扩展的银河晕中相对速度较低的气体的能力有限，因为这些谱线与来自稠密前景气体的更强信号混合在一起。因此，银河系环星系介质(CGM)的含量在|v LSR|≲150 KM S−1上受到的约束很差。为了克服这一复杂的问题，星空探测首次应用了一种使用成对类星体−恒星视线的光谱差分技术来测量银河系环星系介质的模糊含量。我们给出了在哈勃太空望远镜/宇宙起源光谱图中探测到的CIV双星(λλ1548,1550)，这是一种静止框架的紫外线金属线跃迁，它是由30对均匀分布在银河系纬度|b|>；30°的晕星/类星体对组成的光谱。这30颗晕星的距离受到很好的限制(d≈5-14kpc)，并与类星体配对，间隔13.65)=20%[6/30]，这个值明显低于低红移时恒星形成星系的覆盖分数。我们的结果表明，与低红移(z<；0.1)恒星形成晕相比，银河系CGM的大部分CIV追踪日冕物质位于低纬度，或者银河系CGM缺乏温暖的电离物质。
From our position embedded within the Milky Way’s interstellar medium, we have limited ability to detect gas at low relative velocities in the extended Galactic halo because those spectral lines are blended with much stronger signals from dense foreground gas. As a result, the content of the Milky Way’s circumgalactic medium (CGM) is poorly constrained at ∣v LSR∣ ≲150 km s−1. To overcome this complication, the QuaStar survey applies a spectral differencing technique using paired quasar−star sight lines to measure the obscured content of the Milky Way’s CGM for the first time. We present measurements of the C iv doublet (λ λ1548, 1550), a rest-frame UV metal line transition, detected in Hubble Space Telescope/Cosmic Origins Spectrograph spectra of 30 halo-star/quasar pairs evenly distributed across the sky at Galactic latitudes ∣b∣ > 30°. The 30 halo stars have well-constrained distances (d ≈ 5–14 kpc) and are paired with quasars separated by 13.65)= 20% [6/30], a value significantly lower than the covering fraction for star-forming galaxies at low redshift. Our results suggest either that the bulk of Milky Way’s C iv -traced CGM lies at low Galactic latitudes or that the Milky Way’s CGM is lacking in warm, ionized material compared to low-redshift (z < 0.1) star-forming galaxy halos.