nmtdonor210.3.17

 

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Physics Seminar

Date: Thu. 30 Oct, 2014 4:00 pm - 5:00 pm
Duration: 1 Hour
Location: Workman Center

Dr. David Westpfahl, professor in the Physics Department at New Mexico Tech, will present the Physics Seminar. His talk is titled, "Why does the neutral hydrogen in M81 have a central hole?" One of the most prominent features of the neutral hydrogen distribution in the nearby galaxy M81 is its large central hole, 4 kiloparsecs in radius. When the author first asked himself this question there was no route to an answer. Now, thanks to easy access to data archives of ground-based and satellite telescopes, there is. The hole has to be filled with some other gas, otherwise the velocity dispersion of the hydrogen at the edge of the hole would cause it to diffuse inward in a few galactic rotations. Data from the VLA, GALEX, and the Chandra X-ray Observatory reveal the relationship among neutral hydrogen, far UV photons and X-rays. A three-component thermal plasma coincident with the rotation center of M81 provides enough X-rays to ionize the hydrogen in the hole. This is confirmed by an archivel H-alpha image. 4 p.m. in Workman 101

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