Molecular Hydrogen in High-Velocity Clouds
Molecular Hydrogen in High-Velocity Clouds
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高速云中的分子氢
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
B. Savage
中科院分区：
文献类型：
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作者：
P. Richter;K. Sembach;B. Wakker;B. Savage
我们介绍了远紫外光谱探测器在两个银河系高速云（HVCs）中对星际分子氢（H2）的观测。在vLSR = +190 km s-1的最低三个旋转状态（J = 0-2）下，在Seyfert星系Fairall 9的麦哲伦流（丰度~0.3太阳）中检测到分子氢的吸收，产生的总H2柱密度为log N(H2) = 16.40。相比之下，在类星体PG 1259+593 [vLSR = -130 km s-1时log N(H2)≤13.96]的HVC复合物C（丰度~0.1太阳）中没有H2吸收，尽管两个HVC具有相似的log N(H)≈20数量级的H I柱密度。在pg1259 +593的中速拱（IV拱，丰度~1.0太阳）中检测到微弱的H2吸收[vLSR = -55 km s-1时log N(H2) = 14.10, log N(H I) = 19.5]。因此，像复合体C这样缺乏金属和尘埃的光环云似乎无法形成和维持广泛分布的H2，而像IV拱门这样富含金属和尘埃的光环云即使在低H柱密度下也能维持H2。
We present Far Ultraviolet Spectroscopic Explorer observations of interstellar molecular hydrogen (H2) in two Galactic high-velocity clouds (HVCs). Molecular hydrogen absorption is detected in the Magellanic Stream (abundance ~0.3 solar) toward the Seyfert galaxy Fairall 9 in the lowest three rotational states (J = 0-2) at vLSR = +190 km s-1, yielding a total H2 column density of log N(H2) = 16.40. In contrast, no H2 absorption is seen in the HVC Complex C (abundance ~0.1 solar) toward the quasar PG 1259+593 [log N(H2) ≤ 13.96 at vLSR = -130 km s-1], although both HVCs have similar H I column densities on the order of log N(H I) ≈ 20. Weak H2 absorption is detected in the Intermediate-Velocity Arch (IV Arch; abundance ~1.0 solar) toward PG 1259+593 [log N(H2) = 14.10 at vLSR = -55 km s-1 and log N(H I) = 19.5]. It thus appears that metal- and dust-poor halo clouds like Complex C are not able to form and maintain widely distributed H2, whereas metal- and dust-rich halo clouds like the IV Arch can maintain H2 even at low H I column densities.