Ultraviolet photometry from the orbiting astronomical observatory. XIV. an extension of the survey of Lyman-alf absorption from interstellar hydrogen.
1974; IOP Publishing; Volume: 187; Linguagem: Inglês
10.1086/152620
ISSN1538-4357
AutoresE. B. Jenkins, Blair D. Savage,
Tópico(s)Atmospheric Ozone and Climate
Resumoview Abstract Citations (324) References (1) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultraviolet photometry from the Orbiting Astronomical Observatory. XIV. An extension of the survey of Lyman-alpha absorption from interstellar hydrogen. Jenkins, E. B. ; Savage, B. D. Abstract Data from 26 new stars scanned by the Wisconsin far-ultraviolet spectrometer aboard OAO-2 have been combined with an earlier survey of interstellar La absorption reported by Savage and Jenkins, thereby giving us the H I density to a total of 95 stars. We have also made small revisions in the column densities toward 15 of the stars in the original survey, owing to an improvement in our corrections for line blending from nearby stellar features. The new observations help fill in some of the vacant areas in our previous sky coverage and also confirm our earlier conclusions concerning the regional distribution of local interstellar H I. We have again studied the relation between H I column densities and B - V color excesses. The behavior of these quantities suggests H2 formation causes a noticeable depletion of H I when the extinction per unit distance is somewhat larger than average. We have derived NH( )I E(B - V) 7.5 x 1021 atoms mag-1 from those data for which H2 formation is unimportant, and this figure includes an approximate correction for ionization by the star observed. Using the predicted extinction of a recent grain model we find a density ratio of hydrogen to dust of 170. Except for stars closer than 140 pc, our survey is biased toward the selection of stars having low color excesses. As a result, our value of 0.62 atoms cm-2 for must be significantly lower than the true mean space density of interstellar hydrogen. An average reddening of 0.61 mag kpc-1 (Spitzer) combined with our value for NH(tot )/E(B - V) gives 1.5 cm -2 for hydrogen in all forms (atoms, molecules, and protons) within 1 kpc of the Sun. Column densities for Ca ii recently derived by Hobbs and our La results for 25 stars give Ca ll/H = 1.1 x 10- , but the individual values for this ratio show a large dispersion. On the basis of Ca i/Ca u observations by Hobbs and by White, together with an improved estimate for the ultraviolet radiation density by Witt and Johnson, we estimated the correction for ionization and calculated the abundance ratios Ca/H> = 1.7 x 10- and Na/H = 8.2 x 10-8. Subject headings: abundances - interstellar matter - spectra, ultraviolet Publication: The Astrophysical Journal Pub Date: January 1974 DOI: 10.1086/152620 Bibcode: 1974ApJ...187..243J full text sources ADS | data products SIMBAD (41) Related Materials (37) Part 1: 1970ApJ...161..377C Part 2: 1972ApJ...171..293B Part 3: 1972ApJ...172..755W Part 4: 1972ApJ...178..727D Part 5: 1972ApJ...178..189B Part 6: 1972ApJ...178..495D Part 7: 1973ApJ...179..527M Part 8: 1973ApJ...185..577L Part 9: 1973ApJ...185..921E Part 10: 1974ApJ...189..303G Part 11: 1974ApJ...187..521D Part 12: 1973ApJ...186..939H Part 13: 1974ApJ...187..197S Part 15: 1974ApJ...190..319L Part 16: 1974ApJ...191..659S Part 17: 1975ApJ...195..121D Part 18: 1975ApJ...197..379E Part 19: 1975ApJ...199...92S Part 20: 1976ApJ...203..410B Part 21: 1976Ap&SS..41..121K Part 22: 1976ApJ...206..167P Part 23: 1976ApJ...208..135L Part 24: 1976ApJ...208...64L Part 25: 1979ApJ...228...95C Part 26: 1977ApJ...211..207H Part 27: 1978ApJ...219..947L Part 28: 1978ApJ...222..909W Part 29: 1978ApJ...220..582E Part 30: 1979ApJS...39..195C Part 31: 1979ApJ...229..994G Part 32: 1980ApJS...43..501C Part 33: 1979ApJ...228..419W Part 34: 1980ApJ...236..798W Part 35: 1980ApJS...42..283M Part 36: 1984ApJ...281..774C Part 37: 1982ApJ...256....1C Part 38: 1982AJ.....87..849D
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