Bibcode
Jeong, Hyunjin; Yi, Sukyoung K.; Bureau, Martin; Davies, Roger L.; Falcón-Barroso, Jesús; van de Ven, Glenn; Peletier, Reynier F.; Bacon, Roland; Cappellari, Michele; de Zeeuw, Tim; Emsellem, Eric; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Sarzi, Marc; van den Bosch, Remco C. E.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 398, Issue 4, pp. 2028-2048.
Fecha de publicación:
10
2009
Número de citas
84
Número de citas referidas
76
Descripción
We present Galaxy Evolution Explorer far-ultraviolet (FUV) and
near-ultraviolet (NUV) imaging of 34 nearby early-type galaxies from the
SAURON representative sample of 48 E/S0 galaxies, all of which have
ground-based optical imaging from the MDM Observatory. The surface
brightness profiles of nine galaxies (~26 per cent) show regions with
blue UV-optical colours suggesting RSF. Five of these (~15 per cent)
show blue integrated UV-optical colours that set them aside in the NUV
integrated colour-magnitude relation. These are objects with either
exceptionally intense and localized NUV fluxes or blue UV-optical
colours throughout. They also have other properties confirming they have
had RSF, in particular Hβ absorption higher than expected for a
quiescent population and a higher CO detection rate. This suggests that
residual star formation is more common in early-type galaxies than we
are used to believe. NUV blue galaxies are generally drawn from the
lower stellar velocity dispersion (σe <
200kms-1) and thus lower dynamical mass part of the sample.
We have also constructed the first UV Fundamental Planes and show that
NUV blue galaxies bias the slopes and increase the scatters. If they are
eliminated, the fits get closer to expectations from the virial theorem.
Although our analysis is based on a limited sample, it seems that a
dominant fraction of the tilt and scatter of the UV Fundamental Planes
is due to the presence of young stars in preferentially low-mass
early-type galaxies. Interestingly, the UV-optical radial colour
profiles reveal a variety of behaviours, with many galaxies showing
signs of RSF, a central UV-upturn phenomenon, smooth but large-scale age
and metallicity gradients and in many cases a combination of these. In
addition, FUV-NUV and FUV-V colours even bluer than those normally
associated with UV-upturn galaxies are observed at the centre of some
quiescent galaxies. Four out of the five UV-upturn galaxies are slow
rotators. These objects should thus pose interesting challenges to
stellar evolutionary models of the UV upturn.
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