Spectroscopy of star cluster candidates and HII regions in NGC 6822

Citation
R. Chandar et al., Spectroscopy of star cluster candidates and HII regions in NGC 6822, ASTRONOM J, 120(6), 2000, pp. 3088-3097
Citations number
38
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMICAL JOURNAL
ISSN journal
00046256 → ACNP
Volume
120
Issue
6
Year of publication
2000
Pages
3088 - 3097
Database
ISI
SICI code
0004-6256(200012)120:6<3088:SOSCCA>2.0.ZU;2-P
Abstract
We present optical spectroscopy of four star clusters and six H II regions in the nearby, dwarf irregular galaxy NGC 6822. From the data, we estimate ages of 2.5(-1.0)(+1.5) x 10(7), 2.0(-1.0)(+3.0) x 10(8), 1.4(-0.6)(+1.1) x 10(9), and 10 +/- 2 x 10(9) yr for clusters H VI, C21, H VIII, and H VII, respectively. For clusters H VI and H VII we estimate [Fe/H] approximate to -1.46 +/- 0.26 and similar to -2.0, lower than Large and Small Magellanic Cloud clusters at similar ages. Mass estimates for H VI, H VII, and H VIII demonstrate that clusters with typical globular cluster masses (>10(4) M.) have formed over the lifetime of NGC 6822. For six H II regions, ionic abun dances are derived for element species of N, O, S, and Ne. These show that there is a correlation of abundance with position, the highest oxygen abund ance H II regions being located off the main body of the galaxy.