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The Recent Star Formation in NGC 6822: An Ultraviolet Study

Efremova, Boryana V. and Bianchi, Luciana and Thilker, David A. and Neill, James D. and Burgarella, Denis and Wyder, Ted K. and Madore, Barry F. and Rey, Soo-Chang and Barlow, Tom A. and Conrow, Tim and Forster, Karl and Friedman, Peter G. and Martin, D. Christopher and Morrissey, Patrick and Neff, Susan G. and Schiminovich, David and Seibert, Mark and Small, Todd (2011) The Recent Star Formation in NGC 6822: An Ultraviolet Study. Astrophysical Journal, 730 (2). Art. No. 88. ISSN 0004-637X. doi:10.1088/0004-637X/730/2/88.

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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 Å) and near-UV (NUV, 1771-2831 Å) imaging, and ground-based H alpha imaging. From the GALEX FUV image, we define 77 star-forming (SF) regions with area > 860 pc^2, and surface brightness ≾ 26.8 mag (AB) arcsec^(-2), within 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 10^2 M_⊙ to 1.5 x 10^6 M_⊙. 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^(-2) M_⊙ yr^(-1) over the past 100 Myr, and SFR = 1.0 x 10^(-2) M_⊙ yr^(-1) in the most recent 10 Myr. The latter is in agreement with the value that we derive from the Hα luminosity, SFR = 0.008 M_⊙ yr^(-1). The SFR in the most recent epoch becomes higher if we add the SFR = 0.02 M_⊙ yr^(-1) inferred from far-IR measurements, which trace star formation still embedded in dust (age ≾ a few Myr).

Item Type:Article
Related URLs:
URLURL TypeDescription
Thilker, David A.0000-0002-8528-7340
Neill, James D.0000-0002-0466-1119
Madore, Barry F.0000-0002-1576-1676
Forster, Karl0000-0001-5800-5531
Martin, D. Christopher0000-0002-8650-1644
Morrissey, Patrick0000-0001-8177-1023
Seibert, Mark0000-0002-1143-5515
Additional Information:© 2011 American Astronomical Society. Received 2009 April 19; accepted 2011 January 7; published 2011 March 9. We thank Philip Massey for very helpful clarifications on the calibration of the Hα image, Alin Tolea for initial discussions about the source-contour definition, and the anonymous referee for valuable comments. The GALEX data presented in this paper were obtained from the Multimission Archive at the Space Telescope Science Institute (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grantNAG5- 7584 and by other grants and contracts. GALEX (The Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis of the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. The Hα image used in this paper was obtained by Massey et al. (2007a) as part of the Survey of Local Group Galaxies Currently Forming Stars and downloaded from S.-C.R. is supported by the NRF of Korea to the Center for Galaxy Evolution Research.
Group:Space Radiation Laboratory, Space Astrophysics Laboratory
Funding AgencyGrant Number
National Research Foundation of KoreaUNSPECIFIED
Subject Keywords:galaxies: individual (NGC 6822); galaxies: stellar content; Local Group; stars: formation; ultraviolet: stars
Issue or Number:2
Classification Code:PACS: 98.35.Ac; 98.35.Ln; 95.85.Mt; 97.20.Pm; 98.38.Dq
Record Number:CaltechAUTHORS:20110414-085412903
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Official Citation:The Recent Star Formation in NGC 6822: An Ultraviolet Study Boryana V. Efremova, Luciana Bianchi, David A. Thilker, James D. Neill, Denis Burgarella, Ted K. Wyder, Barry F. Madore, Soo-Chang Rey, Tom A. Barlow, Tim Conrow, Karl Forster, Peter G. Friedman, D. Christopher Martin, Patrick Morrissey, Susan G. Neff, David Schiminovich, Mark Seibert and Todd Small doi: 10.1088/0004-637X/730/2/88
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23329
Deposited By: Ruth Sustaita
Deposited On:14 Apr 2011 20:57
Last Modified:09 Nov 2021 16:13

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