May 02, 2012

Carl Heiles, UC-Berkeley

"Phases, Morphologies, and Magnetic Fields in the Diffuse Interstellar Medium"

In this broad-based talk, we describe some aspects of the diffuse interstellar medium (ISM) as revealed by actual data - old and new, radio to X ray.  Page 6 of Bruce Draine's new book, 'Physics of the Interstellar and Intergalactic Medium', lists the four basic phases of the ISM. How about the fifth phase - which seems to be best revealed by interstellar magnetic fields? His Chapter 29 is entitled 'HI Clouds: Observations'. What do HI Clouds look like? Can gravity ever be important for diffuse atomic structures in interstellar space? His page 104 mentions the 'Local Hot Bubble', revealed long ago by the first soft X-Ray emission maps and, also, by the more complete ROSAT maps. But not so fast - it might not be so hot!  Everybody hates magnetic fields--they are hard to observe and hard to treat theoretically. Does the magnetic field really matter at all?