HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C
HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C
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银河高速云的 HST/COS 观测：穿过复杂 C 的四个活动银河核视线
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发表时间：
2011
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通讯作者：
N. Arav
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作者：
J. Shull;Matthew L. Stevans;C. Danforth;S. Penton;F. J. Lockman;N. Arav
我们报告了哈勃太空望远镜（HST）上的宇宙起源光谱仪（COS）拍摄的银河系高速云（HVCs）的紫外光谱，以及绿岸望远镜（Green Bank Telescope）的21厘米新光谱。与以前的HST光谱相比，更宽的光谱覆盖范围和更高的信噪比，提供了更好的HVC吸收速度定义，额外的电离物质（包括高离子），并且提高了晕气体的丰度。配合物C的金属丰度为太阳的10%-30%，离子范围很广，表明它与银河系晕中的热气体有动力学和热相互作用。COS中分辨率G130M （1133-1468 Å）和G160M （1383-1796 Å）光栅的光谱检测到8种低电离态元素（O i, N i, C ii, S ii, Si ii, Al ii, Fe ii, P ii）和3种中、高电离态元素（Si iii, Si iv, C iv, N v）的紫外吸收谱线。我们对Mrk 817， Mrk 290， Mrk 876和PG 1259+593的四个活动星系核视线具有高速的H i和O vi柱密度，分别为19.39-20.05和13.58-14.10，具有大量的运动相关的光电离气体。高离子丰度比与光电离和碰撞电离气体之间的冷却界面一致：N(C iv)/N(O vi)≈0.3 ~ 0.5，N(Si iv)/N(O vi)≈0.05 ~ 0.11，N(N v)/N(O vi)≈0.07 ~ 0.13，N(Si iv)/N(Si iii)≈0.2。
We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21 cm spectra from the Green Bank Telescope. The wide spectral coverage and higher signal-to-noise ratio, compared to previous HST spectra, provide better velocity definition of the HVC absorption, additional ionization species (including high ions), and improved abundances in this halo gas. Complex C has a metallicity of 10%–30% solar and a wide range of ions, suggesting dynamical and thermal interactions with hot gas in the Galactic halo. Spectra in the COS medium-resolution G130M (1133–1468 Å) and G160M (1383–1796 Å) gratings detect ultraviolet absorption lines from eight elements in low-ionization states (O i, N i, C ii, S ii, Si ii, Al ii, Fe ii, P ii) and three elements in intermediate- and high-ionization states (Si iii, Si iv, C iv, N v). Our four active galactic nucleus sight lines toward Mrk 817, Mrk 290, Mrk 876, and PG 1259+593 have high-velocity H i and O vi column densities, 19.39–20.05 and 13.58–14.10, with substantial amounts of kinematically associated photoionized gas. The high-ion abundance ratios are consistent with cooling interfaces between photoionized and collisionally ionized gas: N(C iv)/N(O vi) ≈ 0.3–0.5, N(Si iv)/N(O vi) ≈ 0.05–0.11, N(N v)/N(O vi) ≈ 0.07–0.13, and N(Si iv)/N(Si iii) ≈0.2.