Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.........5d&link_type=abstract
Ph.D. Thesis Wisconsin Univ., Madison.
Astronomy and Astrophysics
Astronomy
2
Galactic Structure, H I Regions, Hydrogen, Interstellar Gas, Lyman Alpha Radiation, Milky Way Galaxy, Spatial Distribution, Galactic Halos, Hot Stars, Line Spectra, Neutral Gases, Ultraviolet Astronomy
Scientific paper
The focus of the thesis is the distribution of neutral hydrogen in the galactic disk and halo. The thesis consists of two projects. The first project is the study of the warp of the outer galaxy, via 21 cm emission. The second project deals with the H I distribution as derived from Ly alpha studies of stars hotter than B2 with the IUE. In the first part, we have used the Bell Laboratories Northern Hemisphere H I survey data of Stark and coworkers. These measurements are well suited for investigations of faint galactic H I emission because the sidelobe contamination of the data is low. We present a series of contour maps of nH. The measurements permit us to probe with reliability the nature of the galactic warp and the extension of the gas to large z in the outer galaxy. For moderate R, the z distribution of the H I is complicated and reveals the existence of a confined component and an extended component. When viewed from the position of the sun, the warped and flaring outer galaxy extends to galactic latitudes as large as +25 degrees. In the second part of the thesis we studied the galactic interstellar H I distribution by analyzing existing absorption line data towards the complete sample of 554 B2 and hotter stars observed at high resolution with the IUE. This study more than doubles the number of lines of sight previously observed. We corrected the measured values of N(H I) for stellar contamination, and discarded approximately 40 percent of the B stars. The final working sample includes 388 stars. We present statistical averages for a number of quantities derived for the sample and study the changes in the H I to dust ratios with distance absolute value of z and with n(H I). The distribution of the gas away from the galactic plane is complex.
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