We use spiral galaxy evolution models to argue that there are substantial variations in stellar mass-to-light ratio (M/L) within and among galaxies. Our models show a strong correlation between stellar M/L and galaxy color. We compare the colors and maximum-disk M/L values of a sample of galaxies to the model color-M/L relation, finding that a Salpeter IMF is too massive but that an IMF with fe...

THE ROLE OF STELLAR FEEDBACK IN GALAXY EVOLUTION

The chemical evolution of the Universe is governed by the chemical yields from stars, which in turn is determined primarily by the initial stellar mass. Even stars as low as 0.9M⊙ can, at low metallicity, contribute to the chemical evolution of elements. Stars less massive than about 10M⊙ experience recurrent mixing events that can significantly change the surface composition of the envelope, w...

A key mystery in stellar magnetohydrodynamics is knowledge of stellar differential rotation. At present, the only practical method for detecting the presence of surface differential rotation for slowly-rotating stars is through the indirect measurement of the stellar butterfly diagram: i.e., the change of rotation period determined from light modulation caused by the change in mean latitude of ...

Using the Hubble Space Telescope/Advanced Camera for Surveys data in the COSMOS field, we systematically searched clumpy galaxies at 0.2 < z < 1.0 and investigated the fraction of clumpy galaxies and its evolution as a function of stellar mass, star formation rate (SFR), and specific SFR (SSFR). The fraction of clumpy galaxies in star-forming galaxies with Mstar > 10 M⊙ decreases with time from...

We present an analysis of the spatial distribution of various stellar populations within the Large and Small Magellanic Clouds. We use optically selected stellar samples with mean ages between ∼ 9 and ∼ 1000 Myr, and existing stellar cluster catalogues to investigate how stellar structures form and evolve within the LMC/SMC. We use two statistical techniques to study the evolution of structure ...

Planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) offer the unique opportunity to study both the population and evolution of low- and intermediate-mass stars, by means of the morphological type of the nebula. Using observations from our LMC PN morphological survey, and including images available in the Hubble Space Telescope Data Archive and published chemical abundances, we find that...

Near the edges of the instability strip the rate of stellar evolution is larger than the growth-rate of the pulsation amplitude, and the same holds whenever the star is engaged in pulsational mode switching. Stellar evolution therefore controls both the onset of pulsation at the edges of the instability strip and of mode switching inside it. Two types of switchings (bifurcations) occur. In a so...

We present a new set of stellar yields obtained from rotating stellar models at solar metallicity covering the massive star range (12–60 M⊙). The stellar models were calculated with the latest version of the Geneva stellar evolution code described in Hirschi et al. (2004). Evolution and nucleosynthesis are in general followed up to silicon burning. The yields of our non–rotating models are cons...