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Tracing OH absorption to illuminate H₂ along the line of sight to Cassiopeia A

Presentation #105.09 in the session Molecular Clouds and the ISM — iPoster Session.

Published onJun 29, 2022
Tracing OH absorption to illuminate H₂ along the line of sight to Cassiopeia A

The dense interstellar medium is defined by regions of molecular hydrogen, or H2. Observations of these regions have presented challenges due to the nature of the dihydrogen molecule and its relative invisibility to the observer. Therefore, other molecules are used to map the dense medium in molecular hydrogen’s place. Carbon monoxide, or CO, is the second most abundant molecule in the interstellar medium and the most common tracer for H2. However, there is a significant fraction of the dense interstellar medium which is CO-dark. The inability to map molecular hydrogen directly is a barrier to precisely studying the dense interstellar medium. Observations of less common gas tracers, such as the hydroxyl radical OH, have the potential to illuminate these CO-dark regions and complement our picture of the dense interstellar medium. This poster presents new observations of OH from the Perseus arm of the Galaxy obtained with the Karl G. Jansky Very Large Array (VLA). By assuming LTE we estimate the amount of H2 traced by OH and compare it to that traced by CO. This comparison suggests a complimentary relationship between both tracers which holds implications to further study of the dense medium and star formation.

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