Issue |
A&A
Volume 475, Number 3, December I 2007
|
|
---|---|---|
Page(s) | 859 - 873 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20078425 | |
Published online | 02 October 2007 |
Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
1
Observatoire de Genève, Université de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland e-mail: Thibaut.Decressin@obs.unige.ch
2
Laboratoire d'Astrophysique de Toulouse et Tarbes, CNRS UMR 5572, OMP, Université Paul Sabatier Toulouse 3, 14 Av. E. Belin, 31400 Toulouse, France
Received:
6
August
2007
Accepted:
18
September
2007
Aims.We analyse the effects of a first generation of fast rotating massive stars on the dynamical and chemical properties of globular clusters.
Methods.We use stellar models of fast rotating massive stars, losing mass through a slow mechanical equatorial winds to produce material rich in H-burning products. We propose that stars with high Na and low O abundances (hereafter anomalous stars) are formed from matter made of slow winds of individual massive stars and of interstellar matter. The proportion of slow wind and of interstellar material is fixed in order to reproduce the observed Li-Na anticorrelation in NGC 6752.
Results.In the case that globular clusters, during their lifetime, did not lose
any stars, we found that to reproduce the observed ratio of normal to
anomalous stars, a flat initial mass function (IMF) is needed, with
typically a slope (a Salpeter's IMF has
). In the case that
globular clusters suffer from an evaporation of normal stars, the IMF
slope can be steeper: to have
, about 96% of the normal stars
would be lost. We make predictions for the distribution of stars as a
function of their [O/Na] and obtain quite reasonable agreement with that
one observed for NGC 6752. Predictions for the number fraction of stars
with different values of helium, of the
/
and
/
ratios are discussed, as well as the expected
relations between values of [O/Na] and those of helium, of [C/N], of
/
and of
/
. Future observations
might test these predictions. We also provide predictions for the present
day mass of the clusters expressed in units of mass of the gas used to
form stars, and for the way the present day mass is distributed between
the first and second generation of stars and the stellar remnants.
Key words: globular clusters: general / globular clusters: individual: NGC 6752 / stars: abundances / stars: luminosity function, mass function / stars: mass-loss / stars: rotation
© ESO, 2007
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