THE RECENT STAR FORMATION IN NGC 6822: AN ULTRAVIOLET STUDY
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
- California Institute of Technology, MC 278-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France)
- Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764 (Korea, Republic of)
- Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Department of Astronomy, Columbia University, New York, NY 10027 (United States)
We characterize the star formation in the low-metallicity galaxy NGC 6822 over the past few hundred million years, using GALEX far-UV (FUV, 1344-1786 A) and near-UV (NUV, 1771-2831 A) imaging, and ground-based H{alpha} imaging. From the GALEX FUV image, we define 77 star-forming (SF) regions with area >860 pc{sup 2}, and surface brightness {approx}<26.8 mag (AB) arcsec{sup -2}, within 0.{sup 0}2 (1.7 kpc) of the center of the galaxy. We estimate the extinction by interstellar dust in each SF region from resolved photometry of the hot stars it contains: E(B - V) ranges from the minimum foreground value of 0.22 mag up to 0.66 {+-} 0.21 mag. The integrated FUV and NUV photometry, compared with stellar population models, yields ages of the SF complexes up to a few hundred Myr, and masses from 2 x 10{sup 2} M{sub sun} to 1.5 x 10{sup 6} M{sub sun}. The derived ages and masses strongly depend on the assumed type of interstellar selective extinction, which we find to vary across the galaxy. The total mass of the FUV-defined SF regions translates into an average star formation rate (SFR) of 1.4 x 10{sup -2} M{sub sun} yr{sup -1} over the past 100 Myr, and SFR = 1.0 x 10{sup -2} M{sub sun} yr{sup -1} in the most recent 10 Myr. The latter is in agreement with the value that we derive from the H{alpha} luminosity, SFR = 0.008 M{sub sun} yr{sup -1}. The SFR in the most recent epoch becomes higher if we add the SFR = 0.02 M{sub sun} yr{sup -1} inferred from far-IR measurements, which trace star formation still embedded in dust (age {approx}< a few Myr).
- OSTI ID:
- 21574846
- Journal Information:
- Astrophysical Journal, Vol. 730, Issue 2; Other Information: DOI: 10.1088/0004-637X/730/2/88; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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