An Old Cluster in NGC 6822 | Zendy

Judith G. Cohen | Zendy; John P. Blakeslee | Zendy

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An Old Cluster in NGC 6822

Author(s) -

Judith G. Cohen,

John P. Blakeslee

Publication year - 1998

Publication title -

the astronomical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.61

H-Index - 271

eISSN - 1538-3881

pISSN - 0004-6256

DOI - 10.1086/300389

Subject(s) - astrophysics , globular cluster , metallicity , physics , irregular galaxy , dwarf galaxy , cluster (spacecraft) , star cluster , galaxy , star formation , hubble sequence , astronomy , local group , galaxy cluster , elliptical galaxy , interacting galaxy , computer science , programming language

We present spectroscopy of two clusters in the dwarf irregular galaxy NGC6822. From these we deduce an age for Cluster VII of 11 Gyr and [Fe/H] = -1.95+/- 0.15 dex. Cluster VII appears to be an analog of the metal-poor galacticglobular clusters. Cluster VI is found to be much younger and more metal rich,with an age of approximately 2 Gyr. Its derived metallicity, [Fe/H], ofapproximately -1.0 dex is comparable to that of the gas seen today in NGC 6822.The existence of a metal-poor old cluster in NGC 6822 rules out models for thechemical evolution of this galaxy with significant prompt initial enhancement.We find that a star formation rate which is constant with time and is within afactor of two of the present star formation rate can reproduce the two pointson the age-metallicity relationship for NGC 6822 over the past 10 Gyr definedby these two clusters.Comment: 8 pages; accepted for publication in A

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