A Comprehensive Survey of Hydrogen Chloride in the Galaxy
Ruisheng Peng, Hiroshige Yoshida, Richard A. Chamberlin, Thomas G., Phillips, Dariusz C. Lis, Maryvonne Gerin

TL;DR
This study presents new submillimeter observations of hydrogen chloride in 25 galactic regions, revealing its widespread presence, variable isotopic ratios, and significant chlorine depletion, providing insights into chemical processes in star-forming environments.
Contribution
It provides the first extensive survey of HCl in diverse galactic environments, including detailed modeling and analysis of chlorine isotopic ratios and depletion factors.
Findings
HCl detected in most sources, often in emission or absorption.
HCl abundance varies with gas density, indicating diverse chemical conditions.
Isotopic ratios suggest localized nucleosynthesis effects and supernova progenitor characteristics.
Abstract
We report new observations of the fundamental transition of HCl (at 625.918GHz) toward a sample of 25 galactic star-forming regions, molecular clouds, and evolved stars, carried out using the Caltech Submillimeter Observatory. Fourteen sources in the sample are also observed in the corresponding H\tscl\ transition (at 624.978GHz). We have obtained clear detections in all but four of the targets, often in emission. Absorptions against bright background continuum sources are also seen in nine cases, usually involving a delicate balance between emission and absorption features. From RADEX modeling, we derive gas densities and HCl column densities for sources with HCl emission. HCl is found in a wide range of environments, with gas densities ranging from to ~cm. The HCl abundance relative to H is in the range of . Comparing with…
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Taxonomy
TopicsAtmospheric Ozone and Climate · Astrophysics and Cosmic Phenomena · Astrophysics and Star Formation Studies
