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ORFEUS-I Observations of Molecular Hydrogen in the Galactic Disk

Published online by Cambridge University Press:  12 April 2016

W. Van Dyke Dixon ,
Mark Hurwitz  and
Stuart Bowyer
W. Van Dyke Dixon
Affiliation:
Space Sciences Laboratory and Center for EUV Astrophysics, University of California, Berkeley, California 94720-5030, U.S.A.
Mark Hurwitz
Affiliation:
Space Sciences Laboratory and Center for EUV Astrophysics, University of California, Berkeley, California 94720-5030, U.S.A.
Stuart Bowyer
Affiliation:
Space Sciences Laboratory and Center for EUV Astrophysics, University of California, Berkeley, California 94720-5030, U.S.A.

Abstract

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We present measurements of interstellar H2 absorption lines in the continuum spectra of seven early-type stars in the Galactic disk at distances between 1 and 4 kpc. The spectra, obtained with the Berkeley EUV/FUV spectrometer on the ORFEUS telescope in 1993 September, have a resolution of 3000 and statistical signal-to-noise ratios between 20 and 80. We determine column densities for each observed rotational level and derive mean excitation temperatures and proton density limits for the H2 clouds along each line of sight. The gross properties of the H2-bearing clouds (e.g., column density, spatial density, cloud size) are consistent with those derived from Copernicus observations, though our lines of sight are much longer, with lower average reddenings and neutral gas densities. We find that the molecular fraction of the neutral hydrogen remains ~ 0.1 out to distances of 4 kpc in the Galactic disk.

Type
Part V Magnetic Fields, Molecular Clouds, and Interstellar Bubbles
Information
International Astronomical Union Colloquium , Volume 166: The Local Bubble and Beyond , 1997 , pp. 261 - 264
Copyright
Copyright © Springer-Verlag 1998

References

Fruscione, A., Hawkins, I., Jelinsky, P., Wiercigroch, A. (1994): ApJS, 94, 127 Google Scholar
Gies, D.R. (1987): ApJS, 64, 545 Google Scholar
Jenkins, E.B. (1978): ApJ, 219, 845 CrossRefGoogle Scholar
Jura, M. (1975): ApJ, 197, 581 Google Scholar
Reach, W.T., Koo, B.-C., Heiles, C. (1994): ApJ, 429, 672 CrossRefGoogle Scholar
Savage, B.D., Bohlin, R.C., Drake, J. F, Budich, W. (1977): ApJ, 216, 291 Google Scholar
Savage, B.D., Massa, D. (1987): ApJ, 314, 380 Google Scholar
Sembach, K.R., Danks, A.C., Savage, B.D. (1993): A&AS, 100, 107 Google Scholar
Shull, J.M., Beckwith, S. (1982): ARA&A, 20, 163 Google Scholar
Snow, T.P. Jr., Jenkins, E.B. (1977): ApJS, 33, 269 Google Scholar
Taresch, G. et al. (1997): A&A, submittedGoogle Scholar
Walborn, N.R. (1973): ApJ, 179, 517 Google Scholar
Walborn, N.R. (1982): ApJS, 48, 145 Google Scholar
Wilson, T.L., Walmsley, C.M. (1989): A&AR, 1, 141 Google Scholar