We have incorporated the latest release of the Padova models into the evolutionary synthesis code Starburst99. The Padova tracks were extended to include the full asymptotic giant branch (AGB) evolution until the final thermal pulse over the mass range 0.9-5 M . With this addition, Starburst99 accounts for all stellar phases that contribute to the integrated light of a stellar population with arbitrary age from the extreme-ultraviolet to the nearinfrared. AGB stars are important for ages between 0.1 and 2 Gyr, with their contribution increasing at longer wavelengths. We investigate similarities and differences between the model predictions by the Geneva and the Padova tracks. The differences are particularly pronounced at ages >1 Gyr, when incompleteness sets in for the Geneva models. We also perform detailed comparisons with the predictions of other major synthesis codes and find excellent agreement. Our synthesized optical colors are compared to observations of old, intermediate-age, and young populations. Excellent agreement is found for the old globular cluster system of NGC 5128 and for old and intermediate-age clusters in NGC 4038/4039. In contrast, the models fail for red supergiant-dominated populations with subsolar abundances. This failure can be traced back to incorrect red supergiant parameters in the stellar evolutionary tracks. Our models and the synthesis code are publicly available as version 5.0 of Starburst99 at

We present and discuss evolutionary synthesis models for massive stellar populations generated with the Starburst99 code in combination with a new set of stellar evolution models accounting for rotation. The new stellar evolution models were compiled from several data releases of the Geneva group and cover heavy-element abundances ranging from twice solar to one fifth solar. The evolution models were computed for rotation velocities on the zero-age main-sequence of 0 and 300 km/s and with the latest revision of stellar mass-loss rates. Since the mass coverage is incomplete, in particular at non-solar chemical composition, our parameter study is still preliminary and must be viewed as exploratory. Stellar population properties computed with Starburst99 and the new evolution models show some marked differences in comparison with models obtained using earlier tracks. Since individual stars now tend to be more luminous and bluer when on the blue side of the Hertzsprung-Russell diagram, the populations mirror this trend. For instance, increases by factors of two or more are found for the light-to-mass ratios at ultraviolet to near-infrared wavelengths, as well as for the output of hydrogen ionizing photons. If these results are confirmed once the evolution models have matured, recalibrations of certain star-formation and initial mass function indicators will be required.Comment: Accepted for publication in Ap

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We analyse the stellar populations of 75 red‐sequence dwarf galaxies in the Coma cluster, based on high signal‐to‐noise ratio spectroscopy from the 6.5‐m MMT. The sample covers a luminosity range 3–4 mag below M★, in the cluster core and in a field centred 1° to the south‐west. We find a strong dependence of the absorption‐line strengths with location in the cluster. Galaxies further from the cluster centre have stronger Balmer lines than inner‐field galaxies of the same luminosity. The magnesium lines are weaker at large radius, while the iron lines are not correlated with radius. Converting the line strengths into estimates of stellar age, metallicity and abundance ratios, we find the gradients are driven by variations in age (>6σ significance) and in the iron abundance Fe/H (∼2.7σ significance). The light element (Mg, C, N, Ca) abundances are almost independent of radius. At radius of times the virial radius), dwarf galaxies have ages ∼3.8 Gyr on average, compared to ∼6 Gyr near the cluster centre. The outer dwarfs are also ∼50 per cent more iron‐enriched, at given luminosity. Our results confirm earlier indications that the ages of red‐sequence galaxies depend on location within clusters, and in Coma in particular. The very strong trends found here suggest that dwarf galaxies are especially susceptible to environmental ‘quenching’, and/or that the south‐west part of Coma is particularly a clear example of recent quenching in an infalling subcluster.