(This page contains information for Astronomy 208 at Harvard University)
The first set of illustrations below is from McKee & Ostriker 1977, ApJ, 218, 418, which presents a theory of the ISM where four phases (shown in figure 1) are important.
The spectrum below shows a sensitive observation of H I gas near b=30 degrees. The Cold Neutral Medium (CNM) gives the narrow main peak, and the Warm Neutral Medium (WNM) gives the broad underlying peak, which is characterized by its much larger thermal velocity width.
More detailed spectra of H I in a nearby high-latitude cloud complex (Ursa Major) which is hanging down from a large H I shell (see Heiles, C. 1979, ApJ, 229, 533-544 and Meyerdierks, H., Heithausen, A. & Reif, K. 1991, A&A, 245, 247) are available on-line through the Web site for Pound & Goodman 1996, ApJ, submitted. A link to a 100-micron IRAS image of the H I shell from Pound & Goodman 1996 shows the Ursa Major Cloud complex highlighted with a black box.
Web page part of: Astronomy 208, The Physics of the Interstellar Medium, Harvard University, Prof. Alyssa A. Goodman
