The ATLAS3D project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

Richard M. McDermid*, Katherine Alatalo, Leo Blitz, Frédéric Bournaud, Martin Bureau, Michele Cappellari, Alison F. Crocker, Roger L. Davies, Timothy A. Davis, P. T. De Zeeuw, Pierre Alain Duc, Eric Emsellem, Sadegh Khochfar, Davor Krajnović, Harald Kuntschner, Raffaella Morganti, Thorsten Naab, Tom Oosterloo, Marc Sarzi, Nicholas Scott & 3 others Paolo Serra, Anne Marie Weijmans, Lisa M. Young

*Corresponding author for this work

Research output: Contribution to journalArticle

190 Citations (Scopus)

Abstract

We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, Σe, R maj e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M{bull's eye}), which themselves formed 90 per cent of their stars by z ~ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.

Original languageEnglish
Pages (from-to)3484-3513
Number of pages30
JournalMonthly Notices of the Royal Astronomical Society
Volume448
Issue number4
DOIs
Publication statusPublished - 21 Apr 2015

Keywords

  • cD
  • Galaxies: abundances
  • Galaxies: elliptical and lenticular
  • Galaxies: evolution
  • Galaxies: stellar content

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