2010MNRAS.403.1213G

We present optical and infrared (IR) integrated colours and surface brightness fluctuation (SBF) magnitudes, computed from stellar population synthesis models that include emission from the dusty envelopes surrounding thermally pulsing asymptotic giant branch (TP-AGB) stars undergoing mass loss. We explore the effects of varying the mass-loss rate by one order of magnitude around the fiducial value, modifying accordingly both the stellar parameters and the output spectra of the TP-AGB stars plus their dusty envelopes. The models are single burst, and range in age from a few Myr to 14Gyr, and in metallicity between Z = 0.0001 and 0.07; they combine new calculations for the evolution of stars in the TP-AGB phase, with star plus envelope spectral energy distributions (SEDs) produced with the radiative transfer code dusty. We compare these models to optical and near-IR data of single AGB stars and Magellanic star clusters. This comparison validates the current understanding of the role of mass loss in determining stellar parameters and spectra in the TP-AGB. However, neither broad-band colours nor SBF measurements in the optical or the near-IR can discern global changes in the mass-loss rate of a stellar population. We predict that mid-IR SBF measurements can pick out such changes, and actually resolve whether a relation between metallicity and mass loss exists.