The ACS LCID project IV: detection of the RGB bump in isolated galaxies of the Local Group - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




The ACS LCID project IV: detection of the RGB bump in isolated galaxies of the Local Group - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We report the detection and analysis of the red giant branch luminosityfunction bump in a sample of isolated dwarf galaxies in the Local Group. Wehave designed a new analysis approach comparing the observed color-magnitudediagrams with theoretical best-fit color-magnitude diagrams derived fromprecise estimates of the star formation histories of each galaxy. This analysisis based on studying the difference between the V-magnitude of the RGB bump andthe horizontal branch at the level of the RR Lyrae instability stripDelta vhbb and we discuss here a technique for reliably measuring thisquantity in complex stellar systems. By using this approach, we find that thedifference between the observed and predicted values of Delta vhbb is +0.13 +-0.14 mag. This is smaller, by about a factor of two, than the well-knowndiscrepancy between theory and observation at low metallicity commonly derivedfor Galactic globular clusters. This result is confirmed by a comparisonbetween the adopted theoretical framework and empirical estimates of theDelta vhbb parameter for both a large database of Galactic globular clustersand for four other dSph galaxies for which this estimate is available in theliterature. We also investigate the strength of the red giant branch bumpfeature R bump, and find very good agreement between the observed andtheoretically predicted R bump values. This agreement supports the reliabilityof the evolutionary lifetimes predicted by theoretical models of the evolutionof low-mass stars.



Author: M. Monelli, S. Cassisi, E. J. Bernard, S. L Hidalgo, A. Aparicio, C. Gallart, E. D. Skillman

Source: https://arxiv.org/







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