文章基本信息

标题：Spotting high-z molecular absorbers using neutral carbon
其他标题：Results from a complete spectroscopic survey with the VLT★
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作者：P. Noterdaeme ; C. Ledoux ; S. Zou 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：612
DOI：10.1051/0004-6361/201732266
语种：English
出版社：EDP Sciences
摘要：While molecular quasar absorption systems provide unique probes of the physical and chemical properties of the gas as well as original constraints on fundamental physics and cosmology, their detection remains challenging. Here we present the results from a complete survey for molecular gas in thirty-nine absorption systems selected solely upon the detection of neutral carbon lines in Sloan Digital Sky Survey (SDSS) spectra, without any prior knowledge of the atomic or molecular gas content. H2is found in all twelve systems (including seven new detections) where the corresponding lines are covered by the instrument setups and measured to have logN(H2) ≳ 18, indicating a self-shielded regime. We also report seven CO detections (7/39) down to logN(CO) ~ 13.5, including a new one, and put stringent constraints onN(CO) for the remaining 32 systems.N(CO) andN(CI) are found to be strongly correlated withN(CO)/N(CI) ~ 1/10. This suggests that the CI-selected absorber population is probing gas deeper than the HI–H2transition in which a substantial fraction of the total hydrogen in the cloud is in the form of H2. We conclude that targeting CI-bearing absorbers is a very efficient way to find high-metallicity molecular absorbers. However, probing the molecular content in lower-metallicity regimes as well as high-column-density neutral gas remains to be undertaken to unravel the processes of gas conversion in normal high-zgalaxies.
关键词：Key wordsenISM: moleculesquasars: absorption lines