Image of Alice in Wonderland at the Mad Hatter's tea party You are cordially invited to afternoon tea and biscuits wine and chocolate

Astronomy Tea Talks at Caltech

Mondays, Hameetman auditorium (Cahill)
Tea:  4.00pm
Talk: 4.15pm

Organized by:

2011 - 2012 season:
21 November 2011 Sugata Kaviraj (Imperial College)

'Early-type galaxies: the last 8 billion years'

I review our current understanding of the star formation histories of early-type galaxies (ETGs), in the context of recent studies of their rest-frame ultraviolet (UV) properties. Contrary to the classical notion of ETGs being old, passively-evolving objects, new rest-frame UV data reveal widespread recent star formation in these galaxies since z~1, with luminous [-23 < M(V) < -21] ETGs forming ~20% of their stellar mass over the last 8 billion years. A strong correspondence between blue UV colours and the presence of morphological disturbances indicates that the star formation is merger-driven. However, the major-merger rate is several factors too low to satisfy the numbers of morphologically-disturbed ETGs, indicating that minor mergers (with mass ratios between 1:4 and 1:10) drive the evolution of ETGs (and massive galaxies in general) after z~1. Using early-release data from the Wide Field Camera 3 (WFC3), I demonstrate how spatially-resolved UV-optical imaging of individual galaxies offers a comprehensive picture of their recent stellar assembly that is far more detailed than what is possible using integrated photometry. I introduce a new Cycle 19 HST-WFC3 programme, which will use UV-optical observations of a representative sample of ETGs to study local star formation and its drivers in unprecedented detail and provide empirical constraints on the (poorly understood) minor-merger process in the local Universe.
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Image of the Mad Hatter from Alice in Wonderland
Last modified on 09th Nov 2011 by Marco Viero.  

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