A Hubble Space Telescope Study of Two HII Regions in NGC 6822

Abstract

We report on the study of the Hubble V and Hubble X H II regions in NGC 6822 with the Hubble Space Telescope employing emission-line and stellar filters. Calibration was made for both data sets, providing magnitudes for the stars and surface brightnesses for the nebulae. The forms of these H II regions are shown to be decidedly more complex than revealed by ground-based images, both having bright cores within more extended emission. The four OB associations within the images are shown to have ages of 5-10 million years. We conclude that the H II regions are sufficiently optically thick to be used as ultraviolet photon counters and hence indicators of the star formation rate.