Bibcode
Morelli, L.; Pompei, E.; Pizzella, A.; Méndez-Abreu, J.; Corsini, E. M.; Coccato, L.; Saglia, R. P.; Sarzi, M.; Bertola, F.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 389, Issue 1, pp. 341-363.
Fecha de publicación:
9
2008
Número de citas
70
Número de citas referidas
62
Descripción
Photometry and long-slit spectroscopy are presented for 14 S0 and spiral
galaxies of the Fornax, Eridanus and Pegasus cluster, and NGC 7582
group. The structural parameters of the galaxies are derived from the
R-band images by performing a two-dimensional photometric decomposition
of the surface brightness distribution. This is assumed to be the sum of
the contribution of a bulge and disc component characterized by
elliptical and concentric isophotes with constant (but possibly
different) ellipticity and position angles. The rotation curves and
velocity dispersion profiles are measured from the spectra obtained
along the major axis of galaxies. The radial profiles of the Hβ, Mg
and Fe line-strength indices are presented too. Correlations between the
central values of Mg2, , Hβ and σ are
found. The age, metallicity and α/Fe enhancement of the stellar
population in the centre and at the radius where bulge and disc give the
same contribution to the total surface brightness are obtained using
stellar population models with variable element abundance ratios. Three
classes of bulges are identified. The youngest bulges (~2 Gyr) with
ongoing star formation, intermediate-age bulges (4-8 Gyr) have solar
metallicity, and old bulges (~10 Gyr) have high metallicity. Most of the
sample bulges display solar α/Fe enhancement, no gradient in age
and a negative gradient of metallicity. The presence of negative
gradient in the metallicity radial profile favours a scenario with bulge
formation via dissipative collapse. This implies strong inside-out
formation that should give rise to a negative gradient in the α/Fe
enhancement too. But, no gradient is measured in the [α/Fe] radial
profiles for all the galaxies, except for NGC 1366. In this galaxy there
is a kinematically decoupled component, which is younger than the rest
of host bulge. It possibly formed by enriched material probably acquired
via interaction or minor merging. The bulge of NGC 1292 is the most
reliable pseudo-bulge of our sample. The properties of its stellar
population are consistent with a slow build-up within a scenario of
secular evolution.
Based on observations made with ESO Telescopes at the La Silla
observatory under programmes 70.B-0486 and 71.B-0202.
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