Metal-rich carbon stars in the Sagittarius dwarf spheroidal galaxy

Eric Lagadec*, Albert A. Zijlstra, G. C. Sloan, Peter R. Wood, Mikako Matsuura, Jeronimo Bernard-Salas, J. A.D.L. Blommaert, M. R.L. Cioni, M. W. Feast, M. A.T. Groenewegen, Sacha Hony, J. W. Menzies, J. Th Van Loon, P. A. Whitelock

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    22 Citations (Scopus)


    We present spectroscopic observations from the Spitzer Space Telescope of six carbon-rich asymptotic giant branch (AGB) stars in the Sagittarius dwarf spheroidal galaxy (Sgr dSph) and two foreground Galactic carbon stars. The band strengths of the observed C2H2 and SiC features are very similar to those observed in Galactic AGB stars. The metallicities are estimated from an empirical relation between the acetylene optical depth and the strength of the SiC feature. The metallicities are higher than those of the Large Magellanic Cloud, and close to Galactic values. While the high metallicity could imply an age of around 1 Gyr, for the dusty AGB stars, the pulsation periods suggest ages in excess of 2 or 3 Gyr. We fit the spectra of the observed stars using the dusty radiative transfer model and determine their dust mass-loss rates to be in the range 1.0-3.3 × 10-8 M yr-1. The two Galactic foreground carbon-rich AGB stars are located at the far side of the solar circle, beyond the Galactic Centre. One of these two stars shows the strongest SiC feature in our present Local Group sample.

    Original languageEnglish
    Pages (from-to)598-608
    Number of pages11
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number1
    Publication statusPublished - Jun 2009


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