Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters

Abstract

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 x=0.55 (a Salpeter's IMF has x=1.35). In the case that globular clusters suffer from an evaporation of normal stars, the IMF slope can be steeper: to have x=1.35, 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 12C/13C and 16O/17O ratios are discussed, as well as the expected relations between values of [O/Na] and those of helium, of [C/N], of 12C/13C and of 16O/17O. 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.

15 pages, 14 figures, accepted in A&A

References in corpus (4)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• Na-O Anticorrelation and HB. II. The Na-O anticorrelation in the globular cluster NGC 6752
• Dynamical masses of two young globular clusters in the blue compact galaxy ESO 338-IG04

Cited by in corpus (11)

• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The evolution of runaway stellar collision products
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• The influence of residual gas expulsion on the evolution of the Galactic globular cluster system and the origin of the Population II halo
• A new imprint of fast rotators: low 12C/13C ratios in extremely metal-poor halo stars
• The evolution of two stellar populations in globular clusters I. The dynamical mixing timescale
• O and Na abundance patterns in open clusters of the Galactic disk
• Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test
• The environment of formation as a second parameter for globular cluster classification
• Physics of rotation in stellar models
• Dynamical mixing of two stellar populations in globular clusters