A COSMOS study of the structure and content of NGC 6822

Abstract

A COSMOS survey of deep Schmidt plates in four colors is used to examine the distribution of stars and unresolved light in the local group dwarf irregular galaxy NGC 6822. Global color-magnitude diagrams and luminosity functions are derived from background-subtracted data. These show more clearly than previous studies the prominence of the main sequence and the comparatively small number of red giants. Maps of stars separated by magnitude and by color, as well as CMDs for various areas, show a wide range in recent histories of star formation over the image. The results are compared to the H I density distribution; most star- forming regions are offset by ~200 pc from H I peaks and some dense H I peaks have no detectable stars. The star formation rate is calculated and compared to those of other galaxies.