Journal article
RED GIANT BRANCH BUMP BRIGHTNESS AND NUMBER COUNTS IN 72 GALACTIC GLOBULAR CLUSTERS OBSERVED WITH THE HUBBLE SPACE TELESCOPE
The Astrophysical journal, Vol.766(2), pp.1-25
04/01/2013
DOI: 10.1088/0004-637X/766/2/77
Abstract
We present the broadest and most precise empirical investigation of red giant branch bump (RGBB) brightness and number counts ever conducted. We implement a new method and use data from two Hubble Space Telescope globular cluster (GC) surveys to measure the brightness and star counts of the RGBB in 72 GCs. The median measurement precision is 0.018 mag in the brightness and 31% in the number counts, respectively, reaching peak precision values of 0.005 mag and 10%. The position of the main-sequence turnoff and the number of horizontal branch stars are used as comparisons where appropriate. Several independent scientific conclusions are newly possible with our parameterization of the RGBB. Both brightness and number counts are shown to have second parameters in addition to their strong dependence on metallicity. The RGBBs are found to be anomalous in the GCs NGC 2808, 5286, 6388, and 6441, likely due to the presence of multiple populations. Finally, we use our empirical calibration to predict the properties of the Galactic bulge RGBB. The updated RGBB properties for the bulge are shown to differ from the GC-calibrated prediction, with the former having lower number counts, a lower brightness dispersion, and a brighter peak luminosity than would be expected from the latter. This discrepancy is well explained by the Galactic bulge having a higher helium abundance than expected from GCs, Delta Y similar to +0.06 at the median metallicity.
Details
- Title: Subtitle
- RED GIANT BRANCH BUMP BRIGHTNESS AND NUMBER COUNTS IN 72 GALACTIC GLOBULAR CLUSTERS OBSERVED WITH THE HUBBLE SPACE TELESCOPE
- Creators
- David M. Nataf - The Ohio State UniversityAndrew P. Gould - The Ohio State UniversityMarc H. Pinsonneault - The Ohio State UniversityAndrzej Udalski - University of Warsaw
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.766(2), pp.1-25
- DOI
- 10.1088/0004-637X/766/2/77
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- Iop Publishing Ltd
- Number of pages
- 25
- Grant note
- PGSD3-403304-2011 / NSERC; Natural Sciences and Engineering Research Council of Canada (NSERC) 246678 / European Research Council under the European Community's Seventh Framework Programme AST-0757888 / NSF; National Science Foundation (NSF)
- Language
- English
- Date published
- 04/01/2013
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701733102771
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