The star-formation histories of early-type galaxies from ATLAS3D

Richard M. McDermid, Katherine Alatalo, Leo Blitz, Maxime Bois, Frédéric Bournaud, Martin Bureau, Michele Cappellari, Alison F. Crocker, Roger L. Davies, Tim A. Davis, P. T. de Zeeuw, Pierre-Alain Duc, Eric Emsellem, Sadegh Khochfar, Davor Krajnović, Harald Kuntschner, Pierre-Yves Lablanche, Rafaella Morganti, Thorsten Naab, Tom OosterlooMarc Sarzi, Nic Scott, Paolo Serra, Anne-Marie Weijmans, Lisa M. Young

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Abstract

We present an exploration of the integrated stellar populations of early-type galaxies (ETGs) from the ATLAS3D survey. We use two approaches: firstly the application of line-indices interpreted through single stellar population (SSP) models, which provide a single value of age, metallicity and abundance ratio. And secondly, by fitting a linear combination of SSP spectra to our data, smoothly weighted in the free parameters of age and metallicity, thereby inferring a star-formation history of these galaxies. Despite the significant differences in these approaches, we obtain generally consistent results, such that galaxies that are more massive appear older with enhanced abundance ratios using line indices, and have shorter star-formation histories weighted to early times. We highlight two limitations of the index-SSP approach. Firstly the SSP-equivalent ages belie the fact that ETGs are overwhelmingly composed of ancient stars. Secondly, the young stellar contributions implied in our star formation histories are required to obtain realistic UV-optical colours. We remark that, even fitting solar-abundance models, we can recover a star-formation duration that correlates with the measured alpha-enhancement, in agreement with other recent work.
Original languageEnglish
Title of host publicationThe Spectral Energy Distribution of Galaxies
PublisherCambridge University Press
Pages244-247
Number of pages4
DOIs
Publication statusPublished - Aug-2012

Publication series

NameProceedings of the International Astronomical Union
NumberS284
Volume7

Keywords

  • galaxies: elliptical and lenticular
  • cD
  • evolution
  • formation
  • stellar content

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