THE RECENT STAR FORMATION IN NGC 6822: AN ULTRAVIOLET STUDY

Journal Article · Fri Apr 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/730/2/88· OSTI ID:21574846

Efremova, Boryana V; Bianchi, Luciana; Thilker, David A ^[1]; Neill, James D; Wyder, Ted K; Barlow, Tom A; Conrow, Tim; Forster, Karl; Friedman, Peter G; Martin, D Christopher; Morrissey, Patrick; Small, Todd ^[2]; Burgarella, Denis ^[3]; Madore, Barry F; Seibert, Mark ^[4]; Rey, Soo-Chang ^[5]; Neff, Susan G ^[6]; Schiminovich, David ^[7]

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1. Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
2. California Institute of Technology, MC 278-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
3. Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12 (France)
4. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
5. Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764 (Korea, Republic of)
6. Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
7. 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, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 730; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DUSTS
ELECTROMAGNETIC RADIATION
EVOLUTION
GALAXIES
MASS
RADIATIONS
STAR EVOLUTION
STARS
ULTRAVIOLET RADIATION