HST/COS检测z = 0.18时DLA中的氘代分子氢
HST/COS Detection of Deuterated Molecular Hydrogen in a DLA at z = 0.18
摘要：
我们报告在$z = 0.18$上检测氘代分子氢。在一个低金属丰度（$Z \sim 0.07Z_\odot$）阻尼Ly $α$系统的HST/COS数据中，在朝向类星体B0120 $-$ 28的$z = 0.18562$处探测到HD和H $_{\rm 2}$，log $N$（H I）= 20.50 $\pm$ 0.10.四个吸收组分在H $_{\rm 2}$中清晰分辨，而两个组分在HD中分辨;大部分分子氢与HD追踪的组分相关。我们发现总柱密度log $N$（HD）= 14.82 $\pm$ 0.15和log $N$（H $_{\rm 2}$）= 20.00 $\pm$ 0.10。该系统具有高分子分数，$f$（H $_{\rm 2}$）= 0.39 $\pm$ 0.10和低HD与H $_{\rm 2}$比率，log（HD/2H $_{\rm 2}$）$= -5.5 \pm 0.2$ dex。在含有大量分子气体的组分中，激发温度$T_{01} = 65 \pm 2$ K低于其它DLA。这些性质与其他已知含有HD的高红移DLA系统中的性质不同，但与在银河系稠密云中观察到的性质一致。
英文摘要：
We report on the detection of deuterated molecular hydrogen, HD, at $z = 0.18$. HD and H$_{\rm 2}$ are detected in HST/COS data of a low metallicity ($Z \sim 0.07Z_\odot$) damped Ly$α$ system at $z = 0.18562$ toward QSO B0120$-$28, with log $N$(H I) = 20.50 $\pm$ 0.10. Four absorption components are clearly resolved in H$_{\rm 2}$ while two components are resolved in HD; the bulk of the molecular hydrogen is associated with the components traced by HD. We find total column densities log $N$(HD) = 14.82 $\pm$ 0.15 and log $N$(H$_{\rm 2}$) = 20.00 $\pm$ 0.10. This system has a high molecular fraction, $f$(H$_{\rm 2}$) = 0.39 $\pm$ 0.10 and a low HD to H$_{\rm 2}$ ratio, log (HD/2H$_{\rm 2}$) $= -5.5 \pm 0.2$ dex. The excitation temperature, $T_{01} = 65 \pm 2$ K, in the component containing the bulk of the molecular gas is lower than in other DLAs. These properties are unlike those in other higher redshift DLA systems known to contain HD, but are consistent with what is observed in dense clouds in the Milky Way.
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