Bibcode
Kuntschner, Harald; Emsellem, Eric; Bacon, Roland; Cappellari, Michele; Davies, Roger L.; de Zeeuw, P. Tim; Falcón-Barroso, J.; Krajnović, Davor; McDermid, Richard M.; Peletier, Reynier F.; Sarzi, Marc; Shapiro, Kristen L.; van den Bosch, Remco C. E.; van de Ven, Glenn
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 408, Issue 1, pp. 97-132.
Advertised on:
10
2010
Número de citas
285
Número de citas referidas
264
Descripción
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 <=3Gyr observed
over the full field-of-view, and sometimes even showing signs of
residual star formation, are restricted to low-mass systems
(σe <= 100kms-1 or ~2 ×
1010Msolar). Spatially restricted cases of young
stellar populations in circumnuclear regions can almost exclusively be
linked to the presence of star formation in a thin, dusty disc/ring,
also seen in the near-UV or mid-IR on top of an older underlying stellar
population.
The flattened components with disc-like kinematics previously identified
in all fast rotators are shown to be connected to regions of distinct
stellar populations. These range from the young, still star-forming
circumnuclear discs and rings with increased metallicity preferentially
found in intermediate-mass fast rotators, to apparently old structures
with extended disc-like kinematics, which are observed to have an
increased metallicity and mildly depressed [α/Fe] ratio compared
to the main body of the galaxy. The slow rotators, often harbouring
kinematically decoupled components (KDC) in their central regions,
generally show no stellar population signatures over and above the
well-known metallicity gradients in early-type galaxies and are largely
consistent with old (>=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.
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