A Spitzer Space Telescope survey of extreme asymptotic giant branch stars in M32

O. C. Jones, I. McDonald, R. M. Rich, F. Kemper, M. L. Boyer, A. A. Zijlstra, George Bendo

    Research output: Contribution to journalArticlepeer-review


    We investigate the population of cool, evolved stars in the Local Group dwarf elliptical galaxy M32, using Infrared Array Camera observations from the Spitzer Space Telescope. We construct deep mid-infrared colour–magnitude diagrams for the resolved stellar populations within 3.5 arcmin of M32's centre, and identify those stars that exhibit infrared excess. Our data are dominated by a population of luminous, dust-producing stars on the asymptotic giant branch (AGB) and extend to approximately 3 mag below the AGB tip. We detect for the first time a sizeable population of ‘extreme’ AGB stars, highly enshrouded by circumstellar dust and likely completely obscured at optical wavelengths. The total dust-injection rate from the extreme AGB candidates is measured to be 7.5 × 10−7 M⊙ yr−1, corresponding to a gas mass-loss rate of 1.5 × 10−4 M⊙ yr−1. These extreme stars may be indicative of an extended star formation epoch between 0.2 and 5 Gyr ago.
    Original languageEnglish
    Pages (from-to)1584-1596
    Number of pages12
    JournalRoyal Astronomical Society. Monthly Notices
    Issue number2
    Publication statusPublished - Jan 2015


    • stars: AGB and post-AGB
    • stars: late-type
    • stars: mass-loss
    • galaxies: individual: M32
    • galaxies: stellar content
    • infrared: stars


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