Dusty Stellar Birth and Death in the Metal-Poor Galaxy NGC 6822

Abstract

The nearby ($\sim$500 kpc) metal-poor ([Fe/H] $\approx$ -1.2; $Z$ $\approx$ 30% $Z_{\odot }$) star-forming galaxy NGC 6822 has a metallicity similar to systems at the epoch of peak star formation. Through identification and study of dusty and dust-producing stars, it is therefore a useful laboratory to shed light on the dust life cycle in the early Universe. We present a catalog of sources combining near- and mid-IR photometry from the United Kingdom Infrared Telescope (UKIRT; $J$, $H$, and $K$) and the $Spitzer$ $Space$ $Telescope$ (IRAC 3.6, 4.5, 5.8, and 8.0 $\mu$m and MIPS 24 $\mu$m). This catalog is employed to identify dusty and evolved stars in NGC 6822 utilizing three color-magnitude diagrams (CMDs). With diagnostic CMDs covering a wavelength range spanning the near- and mid-IR, we develop color cuts using kernel density estimate (KDE) techniques to identify dust-producing evolved stars, including red supergiant (RSG) and thermally-pulsing asymptotic giant branch (TP-AGB) star candidates. In total, we report 1,292 RSG candidates, 1,050 oxygen-rich AGB star candidates, and 560 carbon-rich AGB star candidates with high confidence in NGC 6822. Our analysis of the AGB stars suggests a robust population inhabiting the central stellar bar of the galaxy, with a measured global stellar metallicity of [Fe/H] = -1.286 $\pm$ 0.095, consistent with previous studies. In addition, we identify 277 young stellar object (YSO) candidates. The detection of a large number of YSO candidates within a centrally-located, compact cluster reveals the existence of an embedded, high-mass star-formation region that has eluded previous detailed study. Spitzer I appears to be younger and more active than the other prominent star-forming regions in the galaxy.

Accepted for publication in The Astrophysical Journal; 27 pages, 13 figures, 12 tables (master catalog will be available from publisher)

References in corpus (18)

• Cosmic Star Formation History
• The James Webb Space Telescope
• The ACS Nearby Galaxy Survey Treasury
• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• Spitzer SAGE survey of the Large Magellanic Cloud II: Evolved Stars and Infrared Color Magnitude Diagrams
• AGB stars in the Magellanic Clouds. II. The rate of star formation across the LMC
• Physical Properties of Molecular Clouds at 2 parsec Resolution in the Low-Metallicity Dwarf Galaxy NGC 6822 and the Milky Way
• The Evolution of Massive YSOs in the LMC: Part I. Identification and Spectral Classification
• An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS), II. Discovery of Metal-poor Dusty AGB Stars
• Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG
• An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS), I. Overview
• Spitzer Infrared Spectrographic point source classification in the Small Magellanic Cloud
• The Nature of Infrared Emission in the Local Group Dwarf Galaxy NGC 6822 As Revealed by Spitzer
• The Molecular Interstellar Medium of the Local Group Dwarf NGC6822
• DUSTiNGS III: Distribution of Intermediate-Age and Old Stellar Populations in Disks and Outer Extremities of Dwarf Galaxies
• An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS). IV. Discovery of High-Redshift AGB Analogs
• Emission line objects in NGC 6822. New Planetary Nebula candidates
• Asymptotic Giant Branch Stars in the Nearby Dwarf Galaxy Leo P

Cited by in corpus (8)

• Carbon stars as standard candles: II. The median J magnitude as a distance indicator
• Massive young stellar objects in the Local Group irregular galaxy NGC6822 identified using machine learning
• 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
• Investigating the metallicity dependence of the mass-loss rate relation of red supergiants
• Massive young stellar objects in the Local Group spiral galaxy M33 identified using machine learning
• Euclid: Early Release Observations -- The star cluster systems of the Local Group dwarf galaxies IC 10 and NGC 6822
• The dwarf irregular galaxy NGC 6822. II. Young, intermediate and old stellar populations: comparison between theory and observations
• On the dwarf irregular galaxy NGC 6822. I. Young, intermediate and old stellar populations