The SAURON project - XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

Harald Kuntschner, Eric Emsellem, Roland Bacon, Michele Cappellari, Roger L. Davies, P. Tim de Zeeuw, Jesús Falcón-Barroso, Davor Krajnović, Richard M. McDermid, Reynier F. Peletier, Marc Sarzi, Kristen L. Shapiro, Remco C. E. van den Bosch, Glenn van de Ven

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Abstract

We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hβ, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [α/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [α/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which ~40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of =10Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above ~3.5 × 1010Msolar) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation.
Original languageEnglish
Pages (from-to)97-132
JournalMonthly Notices of the Royal Astronomical Society
Volume408
Issue number1
DOIs
Publication statusPublished - 11-Oct-2010

Keywords

  • galaxies: bulges
  • galaxies: elliptical and lenticular
  • cD
  • galaxies: evolution
  • galaxies: formation
  • galaxies: kinematics and dynamics
  • galaxies: nuclei

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