Issue |
A&A
Volume 403, Number 2, May IV 2003
|
|
---|---|---|
Page(s) | 449 - 462 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20030164 | |
Published online | 06 May 2003 |
Abundance gradients in elliptical galaxies
Dipartimento di Fisica, Università “La Sapienza”, Piazzale A. Moro, 5 00185 Roma, Italy e-mail: lucio.angeletti@uniroma1.it;pietro.giannone@uniroma1.it
Corresponding author: L. Angeletti, lucio.angeletti@uniroma1.it
Received:
27
March
2002
Accepted:
30
January
2003
Abundance gradients predicted by dissipative models of galaxy formation
are studied with the aid of mass models of spherical galaxies obeying the
Sersic law in projection. The link between metallicity and stellar binding
energies and angular momenta is derived from the “concentration model” by
Lynden-Bell ([CITE]) with the addition of a terminal wind and an age spread among the
stellar populations of individual ellipticals.
By using the calibration of the Mg2 index as a function of metallicity
and age from Single-burst Stellar Populations models, the radial profiles of Mg2
are computed for a variety of
models to illustrate the general predictions of the present approach.
We also matched the observed radial profiles of Mg2 in a sample of 11
ellipticals.
We find that observations are reproduced reasonably well in our adopted
approximation and require a considerable degree of dissipation and a metal
yield above the solar value. A terminal wind or an age spread make it easier to fit the Mg2 profiles of
the ellipticals with shallow Mg2 profiles in the innermost regions. However,
model results (with or without an age spread) show that the exact determination of the
free parameters suffers from degeneracy of their effects. Moreover,
model results also suffer from the poorly known effects of non-solar
abundance ratios on index Mg2. Other spectral indices, besides Mg2, and broad-band
colours observed in elliptical galaxies can be examined in the same way with the present
scheme; their study is postponed to a further investigation.
Key words: galaxies: elliptical and lenticular
© ESO, 2003
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