The LMC's Top 250: Classification of the Most Luminous Compact 8 micron Sources in the Large Magellanic Cloud

Abstract

To ascertain the nature of the brightest compact mid-infrared sources in the Large Magellanic Cloud (LMC), we have applied an updated version of the Buchanan et al. (2006) 2MASS-MSX color classification system, which is based on the results of Spitzer Space Telescope spectroscopy, to a mid-infrared (8 micron) flux-limited sample of 250 LMC objects for which 2MASS and MSX photometry is available. The resulting 2MASS-MSX ("JHK8") color-based classifications of these sources, which constitute the most mid-IR-luminous objects in the LMC, were augmented, cross-checked, and corrected where necessary via a variety of independent means, such that only 47 sources retain tentative classifications and only 10 sources cannot be classified at all. The sample is found to consist primarily of carbon-rich AGB stars (~35%), red supergiants (~18%), and compact H II regions (~30%), with additional, small populations of oxygen-rich AGB stars (~4%), dusty, early-type emission-line stars (~3%), and foreground, O-rich AGB stars in the Milky Way (~3%). The very large ratio of C-rich to O-rich objects among the luminous and heavily dust-enshrouded AGB stars in our LMC IR source sample is consistent with the hypothesis that carbon stars form easily in lower metallicity environments. We demonstrate that very luminous C-rich and O-rich AGB stars and red supergiants, identified here primarily on the basis of their JHK8 colors, also appear as distinct clusters in Spitzer IRAC/MIPS color-color diagrams. Thus, in principle, the IRS-based IR photometric classification techniques applied here to the LMC can be applied to any external galaxy whose most luminous IR point sources are detectable and resolvable by 2MASS and Spitzer.

51 pages, 10 figures, 5 tables; submitted to the Astronomical Journal

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Cited by in corpus (10)

• The Mass-Loss Return From Evolved Stars to the LMC: Empirical Relations for Excess Emission at 8 and 24 μm
• Luminosities and mass-loss rates of Local Group AGB stars and Red Supergiants
• A Spitzer/IRS Spectrum of the 2008 Luminous Transient in NGC 300: Connection to Proto-Planetary Nebulae
• Red Supergiant Stars in the Large Magellanic Cloud: I. The Period-Luminosity Relation
• Carriers of the mid-IR emission bands in PNe reanalysed. Evidence of a link between circumstellar and interstellar aromatic dust
• The period-luminosity relation of red supergiants with Gaia DR2
• Mira variables in the Milky Way's nuclear stellar disc: discovery and classification
• Hunting for C-rich long-period variable stars in the Milky Way's bar-bulge using unsupervised classification of Gaia BP/RP spectra
• On Granulation and Irregular Variation of Red Supergiants
• Nebular C IV 1550 Imaging of the Metal-Poor Starburst Mrk 71: Direct Evidence of Catastrophic Cooling