The SAURON project - VIII. OASIS/CFHT integral-field spectroscopy of elliptical and lenticular galaxy centres

Richard M. Mcdermid*, Eric Emsellem, Kristen L. Shapiro, Roland Bacon, Martin Bureau, Michele Cappellari, Roger L. Davies, Tim De Zeeuw, Jesús Falcón-Barroso, Davor Krajnović, Harald Kuntschner, Reynier F. Peletier, Marc Sarzi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

160 Citations (Scopus)


We present high spatial resolution integral-field spectroscopy of 28 elliptical (E) and lenticular (SO) galaxies from the SAURON representative survey obtained with the OASIS spectrograph during its operation at the Canada-France-Hawaii Telescope. These seeing-limited observations explore the central 8 × 10 arcsec 2 (typically 1 kpc diameter) regions of these galaxies using a spatial sampling four times higher than SAURON (0.27-arcsec versus 0.94-arcsec spatial elements), resulting in almost a factor of 2 improvement in the median point spread function. These data allow accurate study of the central regions to complement the large-scale view provided by SAURON. Here we present the stellar and gas kinematics, stellar absorption-line strengths and nebular emission-line strengths for this sample. We also characterize the stellar velocity maps using the 'kinemetry' technique, and derive maps of the luminosity-weighted stellar age, metallicity and abundance ratio via stellar population models. We give a brief review of the structures found in our maps, linking also to larger-scale structures measured with SAURON. We present two previously unreported kinematically decoupled components (KDCs) in the centres of NGC 3032 and NGC 4382. We compare the intrinsic size and luminosity-weighted stellar age of all the visible KDCs in the full SAURON sample, and find two types of components: kiloparsec-scale KDCs, which are older than 8 Gyr, and are found in galaxies with little net rotation; and compact KDCs, which have intrinsic diameters of less than a few hundred parsec, show a range of stellar ages from 0.5 to 15 Gyr (with 5/6 younger than 5 Gyr), are found exclusively in fast-rotating galaxies, and are close to counter-rotating around the same axis as their host. Of the seven galaxies in the SAURON sample with integrated luminosity-weighted ages less than 5 Gyr, five show such compact KDCs, suggesting a link between counter-rotation and recent star formation. We show that this may be due to a combination of small sample size at young ages, and an observational bias, since young KDCs are easier to detect than their older and/or corotating counterparts.

Original languageEnglish
Pages (from-to)906-958
Number of pages53
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - Dec 2006
Externally publishedYes


  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: ISM
  • Galaxies: kinematics and dynamics
  • Galaxies: structure


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