论文标题
高红移时极强的DLA：汽油冷却和h $ _2 $编队
Extremely strong DLAs at high redshift: Gas cooling and H$_2$ formation
论文作者
论文摘要
我们对七个候选者的VLT/X射手进行了光谱调查。我们证实了极高的柱密度，尽管比四个系统的原始ESDLA定义略低（0.1〜DEX）。我们测量了所有系统的低离世金属丰度和尘埃灭绝。 For two systems we also found strong associated H$_2$ absorption $\log N(\text{H$_2$)[cm$^{-2}$]}=18.16\pm0.03$ and $19.28\pm0.06$ at $z=3.26$ and $2.25$ towards J2205+1021 and J2359+1354, respectively), while for the剩下的五个，我们测量了h $ _2 $列密度的保守上限，通常是$ \ log n（\ text {h $ _2 $）[cm $^{ - 2} $]} <17.3 $。与总体阻尼Lyman-$α$人口（$ \ sim 5-10 $％）相比，高圆柱密度的H $ _2 $检测率（$ 10-55 $％，在68％的置信度下）确认了以前的工作。我们发现，这七个ESDLA具有与先前研究的类星体和伽马射线爆发余粒相似的观察到的特性，这表明它们探测了星系的内部区域。我们在激发的精细结构水平上使用大量的电离碳来通过CII $λ$ 158 $μ$ M的排放来计算冷却速率，并将它们与文献中受损的Lyman-$α$系统的冷却速率进行比较。我们发现，ESDLA的冷却速率分布也具有与先前对一般（大多数较低HI柱密度）降低的lyman-$α$种群相同的双峰性。
We present a spectroscopic investigation with VLT/X-shooter of seven candidate extremely strong damped Lyman-$α$ absorption systems (ESDLAs, $N(\text{HI})\ge 5\times 10^{21}$ cm$^{-2}$) observed along quasar sightlines. We confirm the extremely high column densities, albeit slightly (0.1~dex) lower than the original ESDLA definition for four systems. We measured low-ionisation metal abundances and dust extinction for all systems. For two systems we also found strong associated H$_2$ absorption $\log N(\text{H$_2$)[cm$^{-2}$]}=18.16\pm0.03$ and $19.28\pm0.06$ at $z=3.26$ and $2.25$ towards J2205+1021 and J2359+1354, respectively), while for the remaining five we measured conservative upper limits on the H$_2$ column densities of typically $\log N(\text{H$_2$)[cm$^{-2}$]}<17.3$. The increased H$_2$ detection rate ($10-55$% at 68% confidence level) at high HI column density compared to the overall damped Lyman-$α$ population ($\sim 5-10$%) confirms previous works. We find that these seven ESDLAs have similar observed properties as those previously studied towards quasars and gamma-ray burst afterglows, suggesting they probe inner regions of galaxies. We use the abundance of ionised carbon in excited fine-structure level to calculate the cooling rates through the CII $λ$158$μ$m emission, and compare them with the cooling rates from damped Lyman-$α$ systems in the literature. We find that the cooling rates distribution of ESDLAs also presents the same bimodality as previously observed for the general (mostly lower HI column density) damped Lyman-$α$ population.
