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Astronomy Seminar Series artwork
April 3, 202311:30 am – 12:30 pm (CDT)

Shedding Light on the Dark Molecular Gas: OH as a Tracer for Dark H2 in the Galaxy and Beyond


Michael Busch (University of California, San Diego)



Mitchell Institute for Fundamental Physics & Astronomy

College Station, Texas 77843

Event Details

The intersection between the atomic and molecular interstellar medium (ISM) is still relatively mysterious. In the past two decades, indirect gas tracers such as gamma-ray and dust emission have implied the existence of abundant molecular hydrogen (H2) not traced by our canonical molecular tracer, the CO molecule. In this talk I will review recent efforts in using the OH molecule at 18cm to trace the large-scale Galactic “CO-dark” H2 with the 100m Green Bank Telescope (GBT). I will talk about the serendipitous discovery of an immense amount of dark H2 in the Outer Galaxy in the form of a diffuse disk, co-spatial with the atomic ISM phase. I will also discuss current work combining SOFIA 2.5 THz data and 18cm OH VLA data to constrain the excitation of the OH ground-state and discuss future potential work with mapping OH with radio telescopes around the world.

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