Sign on

SAO/NASA ADS Astronomy Abstract Service


· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· arXiv e-print (arXiv:astro-ph/9509063)
· References in the article
· Citations to the Article (189) (Citation History)
· Refereed Citations to the Article
· Also-Read Articles (Reads History)
· HEP/Spires Information
·
· Translate This Page
Title:
Globular Cluster Ages and the Formation of the Galactic Halo
Authors:
Chaboyer, Brian; Demarque, P.; Sarajedini, Ata
Publication:
Astrophysical Journal v.459, p.558 (ApJ Homepage)
Publication Date:
03/1996
Origin:
APJ
Astronomy Keywords:
GALAXY: FORMATION, GALAXY: HALO, GALAXY: GLOBULAR CLUSTERS: GENERAL, STARS: HERTZSPRUNG-RUSSELL DIAGRAM, STARS: EVOLUTION, STARS: INTERIORS
DOI:
10.1086/176921
Bibliographic Code:
1996ApJ...459..558C

Abstract

Main-sequence turnoff magnitudes from the recent set of Yale isochrones published by Chaboyer et al. in 1995 have been combined with a variety of relations for the absolute magnitude of RR Lyrae stars [Mv(RR)] to calibrate age as a function of the difference in magnitude between the main-sequence turnoff and the horizontal branch (A VHToB). A best estimate for the calibration of Mv(RR) is derived from a survey of the current literature: Mv(RR) = 0.20[Fe/H] + 0.98. This estimate, together with other calibrations (with slopes ranging from 0.15 to 0.30), has been used to derive A VTHoB ages for 43 Galactic globular clusters. Independent of the choice of Mv(RR), there is no strong evidence for an age- Galactocentric distance relationship among the 43 globular clusters. However, an age-metallicity relation exists, with the metal-poor clusters being the oldest. A study of the age distribution reveals that an age range of 5 Gyr exists among the bulk of the globular clusters. In addition, about 10% of the sample are substantially younger, and including them in the analysis increases the age range to 9 Gyr. Once again, these statements are independent of the Mv(RR) relation. Evidence for age being the second parameter governing horizontal-branch morphology is found by comparing the average A VHToB age of the second parameter clusters to the normal clusters. The second parameter clusters are found to be on average 2-3 Gyr younger than the other clusters, which is consistent with age being the second parameter. These results suggest that globular clusters were formed over an extended period of time, with progressively more metal-rich globular clusters ([Fe/H] - 1.7) being formed at later times.

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences



More Article Retrieval Options

HELP for Article Retrieval


Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)

  New!

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints