1998/03/04 by Judith G. Cohen, John P. Blakeslee · 27 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Cluster (spacecraft) #Dwarf galaxy #Elliptical galaxy #Galaxy #Galaxy cluster #Globular cluster #Hubble sequence #Interacting galaxy #Irregular galaxy #Local Group #Metallicity #Physics #Star cluster #Star formation #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/300389
published in The Astronomical Journal 115(6), 2356-2358 (Institute of Physics) · 8 pages; accepted for publication in AJ
arxiv created 1998/03/04 · openalex publication_date 1998/06/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
We present spectroscopy of two clusters in the dwarf irregular galaxy NGC 6822. 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 Galactic globular 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] ≈ -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 the chemical evolution of this galaxy with significant prompt initial enhancement. We find that a star formation rate that is constant with time and is within a factor of 2 of the present star formation rate can reproduce the two points on the age-metallicity relationship for NGC 6822 over the past 10 Gyr defined by these two clusters.