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2005AJ....130.2087D - Astron. J., 130, 2087-2103 (2005/November-0)
The evolved stellar content of NGC 147, NGC 185, and NGC 205.
DAVIDGE T.J.
Abstract (from CDS):
The C star contents of the three galaxies are compared in two ways. First, the notion of a specific frequency measurement for C stars, in which C star counts per unit magnitude are normalized to a common integrated K-band brightness using published surface photometry, is introduced. The specific frequencies of C stars outside the areas of most recent star formation agree in all three galaxies. Second, comparisons are made using the integrated brightness from C stars, which is normalized to the integrated light from M giants and the integrated light from all stars. The fractional contribution made by C stars to the total AGB light in the K-band is found to be highest in NGC 147 and lowest in the central regions of NGC 205, which is qualitatively consistent with model predictions. The fractional contribution that C stars make to the total K-band light is found to be constant both within and between galaxies, with C stars contributing 2% of the total K-band light. We conclude that, when averaged over timescales of a few gigayears, these galaxies have turned similar fractions of gas and dust, normalized according to total galaxy mass, into stars. We argue that the material for star formation likely originated in well-regulated reservoirs and demonstrate that the mass of gas needed to fuel star formation during intermediate epochs could have been supplied by winds from evolved stars. Finally, multiepoch data are used to investigate the incidence of long-period variables (LPVs) in NGC 185 and NGC 205. While tight constraints cannot be placed on the LPV content of NGC 205, roughly 70% of the stars with MK between -7.5 and -8.0 in the central regions of NGC 185 appear to be LPVs with amplitudes similar to those of LPVs in the LMC.
Abstract Copyright: ∼
Journal keyword(s): Galaxies: Evolution - Galaxies: Individual: NGC Number: NGC 147 - Galaxies: Individual: NGC Number: NGC 185 - Galaxies: Individual: NGC Number: NGC 205 - Galaxies: Stellar Content - Stars: AGB and Post-AGB - Stars: Carbon
Simbad objects: 14
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