Tracers of Stellar Mass-loss - II. Mid-IR Colors and Surface Brightness Fluctuations

Abstract

I present integrated colors and surface brightness fluctuation magnitudes in the mid-IR, derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14 Gyr, and comprise metallicities between $Z$= 0.0001 and $Z$ = 0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of "extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5 um and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100 Myr and 2-3 Gyr.

32 pages, 20 figures, 5 tables, 3 machine readable tables; accepted for publication in The Astrophysical Journal

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Cited by in corpus (4)

• Infrared Properties of Asymptotic Giant Branch Stars in Our Galaxy and the Magellanic Clouds
• Surface Brightness Fluctuation spectra to constrain stellar population properties
• Yonsei Evolutionary Population Synthesis (YEPS) Model. III. Surface Brightness Fluctuation of Normal and Helium-enhanced Simple Stellar Populations
• On the Thermally Pulsing Asymptotic Giant Branch Contribution to the Light of Nearby Disk Galaxies