"The Evolved-Star Dust Budget in Nearby Galaxies"

Sundar Srinivasan (ASIAA, Taiwan)

Abstract
The injection of metal-rich material from dusty red supergiants (RSGs) and asymptotic giant branch (AGB) stars drives the chemical evolution of galaxies and the formation of the next generation of stars. It is therefore critical to constrain the dust budget from these evolved objects. For this purpose, we constructed the Grid of RSG and AGB ModelS (GRAMS, Sargent et al. 2011, Srinivasan et al. 2011), which we subsequently used to fit the multi-wavelength information for RSG and AGB candidates in the Magellanic Clouds obtained from the SAGE (Surveying the Agents of Galaxy Evolution, Meixner et al. 2006) survey. The results for the Large Magellanic Cloud (Riebel et al. 2012) show that the cumulative dust ejection rate is much smaller than that needed to explain the current dust mass in the interstellar medium (ISM). We also find a similar result for the Small Cloud (Boyer et al. 2012, Srinivasan et al. in prep).

In this talk, I will provide a brief introduction to the field of dusty AGB stars and summarize our work on the AGB dust return in nearby galaxies. If time permits, I will also discuss a possible solution to the "missing dust" problem.

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Peter Scicluna (ESO)

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Simon Lilly

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Gráinne Costigan (ESO)

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Andrea Miglio

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Anne Dutrey

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Danail Obreschkow (ICRAR, Univ. of Western Australia)

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"Early-type galaxies: the last 10 billion years"

Sugata Kaviraj (Oxford University, UK)

Abstract
I review our current understanding of the formation of early-type galaxies (ETGs), in the context of studies that exploit rest-frame UV-optical photometry. I show that, contrary to our classical notion of them being old and passively evolving, ETGs host widespread star formation at late epochs via persistent minor merging, which contributes 20% of their stellar mass at the present day. Similarly, while our traditional view has been that ETGs are remnants of gas-rich major mergers at high redshift, I present empirical evidence that argues against major mergers as the dominant mechanism for the formation of these systems in the early Universe. Notwithstanding their apparent homogeneity today, ETGs are a rather heterogeneous population of galaxies, in which early mass growth was likely driven either by direct accretion ("cold flows") or minor mergers at high redshift.