30-micron sources in galaxies with different metallicities

Abstract

We present an analysis and comparison of the 30 micron dust features seen in the Spitzer Space Telescope spectra of 207 carbon-rich asymptotic giant branch (AGB) stars, post-AGB objects, and planetary nebulae located in the Milky Way, the Magellanic Clouds (MCs), or the Sagittarius dwarf spheroidal galaxy (Sgr dSph), which are characterised by different average metallicities. We investigated whether the formation of the 30 micron feature carrier may be a function of the metallicity. Through this study we expect to better understand the late stages of stellar evolution of carbon-rich stars in these galaxies. Our analysis uses the `Manchester method' as a basis for estimating the temperature of dust for the carbon-rich AGB stars and the planetary nebulae in our sample. We used a black-body function with a single temperature deduced from the Manchester method or its modification to approximate the continuum under the 30 micron feature. The most important conclusion of our work is the fact that the formation of the 30 micron feature is affected by metallicity. Specifically that, as opposed to more metal-poor samples of AGB stars in the MCs, the feature is seen at lower mass-loss rates, higher temperatures, and has seen to be more prominent in Galactic carbon stars. The averaged feature (profile) in the AGB, post-AGB objects, and PNe seems unaffected by metallicity at least between a fifth and solar metallicity, but in the case of PNe it is shifted to significantly longer wavelengths.

46 pages, 46 figures

References in corpus (11)

• The Second-Generation Guide Star Catalog: Description and Properties
• Formation of fullerenes in H-containing Planetary Nebulae
• A Spitzer mid-infrared spectral survey of mass-losing carbon stars in the Large Magellanic Cloud
• An evolutionary catalogue of Galactic post-AGB and related objects
• Carbon-rich dust past the asymptotic giant branch: aliphatics, aromatics, and fullerenes in the Magellanic Clouds
• CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph Sources. II. High-resolution observations
• Spitzer Infrared Spectrograph Observations of Magellanic Cloud Planetary Nebulae: the nature of dust in low metallicity circumstellar ejecta
• The mixed chemistry phenomenon in Galactic Bulge PNe
• Discovery of Extreme Carbon Stars in the Large Magellanic Cloud
• Metal-rich carbon stars in the Sagittarius Dwarf Spheroidal galaxy
• Variability in Proto-Planetary Nebulae: III. Light Curve Studies of Magellanic Cloud Carbon-Rich Objects

Cited by in corpus (2)

• Understanding the evolution and dust formation of carbon stars in the LMC with a look at the JWST
• Molecular gas in 21 and 30 micron sources: the 2\,mm and 1.3\,mm spectra of IRAS\,21318+5631 and 22272+5435