Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001aas...198.9301p&link_type=abstract
American Astronomical Society, 198th AAS Meeting, #93.01; Bulletin of the American Astronomical Society, Vol. 33, p.1178
Astronomy and Astrophysics
Astrophysics
1
Scientific paper
Determining the properties of remote globular clusters and elliptical galaxies using evolutionary population synthesis requires a library of model stellar fluxes. We report here a first step toward providing a library that includes nonsolar abundances, based on calculations from first principles. These calculations are calibrated here by modeling the mid-UV spectra of the Sun and nine nearby, near-main-sequence stars of types F and G with metallicities from solar to 1/100 solar. Stellar temperatures were first determined to +/-50K by modeling mid-UV and optical echelle spectra simultaneously, fitting the slope of the mid-UV in the extremely metal-poor stars and the Hα profiles and the strengths of high-excitation atomic lines in the more metal-rich ones. The mid-UV line list was then modified to match the spectra line-by-line at high resolution. The resulting spectra provide a good fit over the range 2300A - 3100A at metallicities 1/10 solar or less, but the fit deteriorates below 2900A at solar metallicity because lines are seen in the spectra that are not yet identified in the laboratory, and so are missing from the list. Nonetheless, we find that temperatures are tightly constrained at low metallicities, and the strengths of lines redward of 2900A, notably OH, are well reproduced at all metallicities by the calculations. This allows us to constrain the oxygen abundances of the stars of all metallicities, and to provide an initial look at the behavior of line-strength indices commonly applied to the spectra of the integrated light of old stellar systems. Support for this work was provided by NASA Astrophysics Data Program contract S-92512-Z and HST grants GO-07395, GO-07402, and AR-8371 to Astrophysical Advances, and by NASA ADP grant NAG5-7104 and NASA LTSA grant NAG 5-6403 to the University of Virginia.
Dorman Ben
Peterson Ruth C.
Rood Robert T.
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