The Recent Star Formation in NGC 6822: an Ultraviolet Study

Abstract

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 Ha imaging. From 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 0.2deg (1.7kpc) 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 0.22mag up to 0.66+-0.21mag. 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 2x10^2 Msun to 1.5x10^6 Msun. 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 1.4x10^-2 Msun/yr over the past 100 Myr, and SFR=1.0x10^-2 Msun/yr in the most recent 10 Myr. The latter is in agreement with the value that we derive from the Ha luminosity, SFR=0.008 Msun/yr. The SFR in the most recent epoch becomes higher if we add the SFR=0.02 Msun/yr inferred from far-IR measurements, which trace star formation still embedded in dust (age <= a few Myr).

Accepted for publication in ApJ, 21 pages, 6 figures, 3 tables

References in corpus (7)

• The GALEX Ultraviolet Atlas of Nearby Galaxies
• Radial variation of attenuation and star formation in the largest late-type disks observed with GALEX
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• UV Radiation Fields Produced by Young Embedded Star Clusters
• The Nature of Infrared Emission in the Local Group Dwarf Galaxy NGC 6822 As Revealed by Spitzer
• An Ultraviolet Study of Star-Forming Regions in M31
• The recent star formation in NGC 6822 from HST imaging

Cited by in corpus (20)

• Revised Catalog of GALEX Ultraviolet Sources. I. The All-sky Survey: GUVcat_AIS
• Low CO Luminosities in Dwarf Galaxies
• Legacy ExtraGalactic UV Survey (LEGUS) with The Hubble Space Telescope. I. Survey Description
• Unveiling the corona of the Milky Way via ram-pressure stripping of dwarf satellites
• The Ultraviolet Sky: An Overview from the GALEX Surveys
• Physical Properties of Molecular Clouds at 2 parsec Resolution in the Low-Metallicity Dwarf Galaxy NGC 6822 and the Milky Way
• Red Supergiant Stars as Cosmic Abundance Probes: KMOS Observations in NGC 6822
• The Galaxy Evolution Explorer (GALEX). Its legacy of UV surveys, and science highlights
• On the evolutionary and pulsation mass of Classical Cepheids: III. the case of the eclipsing binary Cepheid CEP0227 in the Large Magellanic Cloud
• Tracing rejuvenation events in nearby S0 galaxies
• Spectra probing the number ratio of C- to M-type AGB stars in the NGC 6822 galaxy
• Massive young stellar objects in the Local Group irregular galaxy NGC6822 identified using machine learning
• Ca II triplet spectroscopy of RGB stars in NGC 6822: kinematics and metallicities
• Evolved Massive Stars at Low-metallicity IV. Using 1.6 $\mu$m "H-bump" to identify red supergiant stars: a case study of NGC 6822
• The Young Stellar Population of the metal-poor galaxy NGC 6822
• The Panchromatic Hubble Andromeda Treasury. VI. The reliability of far-ultraviolet flux as a star formation tracer on sub-kpc scales
• Gas dynamics and star formation in NGC 6822
• Probing the Infrared/Radio correlation of the full IRAS Revised Bright Galaxy Sample with MeerKAT and the VLA
• Euclid: Early Release Observations -- The star cluster systems of the Local Group dwarf galaxies IC 10 and NGC 6822
• The universality of the relation between magnetic fields and star formation in galaxies