Results 271 to 280 of about 205,088 (284)
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AIP Conference Proceedings, 1989
In an attempt to discover regions of very low heavy element abundance, we have observed H II regions in 7 nearby, very low luminosity dwarf irregular galaxies. All yield oxygen abundances of less than one‐tenth of the solar value, and three are within a factor of two of the lowest oxygen abundance ever detected in an H II region.
Evan D. Skillman, Robert C. Kennicutt
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In an attempt to discover regions of very low heavy element abundance, we have observed H II regions in 7 nearby, very low luminosity dwarf irregular galaxies. All yield oxygen abundances of less than one‐tenth of the solar value, and three are within a factor of two of the lowest oxygen abundance ever detected in an H II region.
Evan D. Skillman, Robert C. Kennicutt
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2001
To start things going, the following topics were suggested:* 1. Reliability of abundances Stars vs H ii regions H ii classical diagnostics Effects of shocks and inhomogeneities on H ii-region diagnostics H n new diagnostics Can reliable H ii-region diagnostics be developed for high metallicity?
Michael Edmunds, B. E. J. Pagel
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To start things going, the following topics were suggested:* 1. Reliability of abundances Stars vs H ii regions H ii classical diagnostics Effects of shocks and inhomogeneities on H ii-region diagnostics H n new diagnostics Can reliable H ii-region diagnostics be developed for high metallicity?
Michael Edmunds, B. E. J. Pagel
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Nebulae and abundances in galaxies
Publications of the Astronomical Society of the Pacific, 1986Some current problems related to abundances in H II regions are briefly reviewed. For H II regions with measured electron temperatures, the discrepancy in O/H between the sun and the Orion Nebula is stressed. Studies of abundance and temperature variations within H II regions in NGC 604 are summarized.
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The evolution of abundances in the galaxy
AIP Conference Proceedings, 1989This very brief review of the evolution of the abundances in our Galaxy first recalls the main observational facts regarding such abundances which have to be taken into account by any model of chemical evolution of our Galaxy. After having defined what are the crucial parameters which define such models, the emphasis is made on two approaches: the ...
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Molecular Abundances in Galaxies
AIP Conference Proceedings, 2006Two topics are discussed here. The first is an observational study on molecular abundance in nearby (< 10 Mpc) gas‐rich galaxies based on our ammonia survey and on data in literature. As a result, a systematically peculiar molecular abundance was found in a famous starburst galaxy M 82 regarding the formation mechanisms of molecules.
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Lithium abundance at the formation of the Galaxy
Nature, 1982The observed abundance of lithium in population I stars (young stars)1 seems to have been stable during the past 5 × 109 yr (ref. 2). This stability has been used previously1,3 to estimate the abundance of lithium at the time of formation of the Galaxy and at pre-galactic times1,3. But because the basis for this estimate was not completely satisfactory,
F. Spite, M. Spite
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Chemical Abundances in Galaxies
1988This article is intended as a brief overview of chemical abundances in galaxies other than our own. Attention is concentrated on global properties of ellipticals and spirals, and the methods by which abundances are estimated. References are predominantly to work which has appeared since the review of Pagel and Edmunds (1981).
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Chemical Abundances and Galaxy Evolution [PDF]
, 1984 The chemical abundance characteristics of two comparatively structurally simple classes of galaxies, the ellipticals and irregulars, are briefly reviewed. Neither of these types of galaxies have properties which are fully consistent with the quantitative predictions of basic chemical evolution models. Possible sources for discrepancies are discussed in
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Abundances in dwarf irregular galaxies
Publications of the Astronomical Society of the Pacific, 1986The results of abundance studies of dwarf irregular galaxies and similar objects are reviewed with special attention to variations in the CNO element group. Observations of the forbidden N II and semiforbidden C III lines in the most metal-poor galaxy known, IZw 18, are presented for the first time and CNO abundances are derived via a photoionization ...
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