Self-enrichment in globular clusters

I. An analytic approach

¹ University Observatory of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: recchi@astro.univie.ac.at
² Institut für Theoretische Physik und Astrophysik, Kiel University, Olshausenstrasse 40, 24098 Kiel, Germany
³ INAF, Osservatorio Astronomico di Trieste, via G.B. Tiepolo, 11, 34131 Trieste, Italy e-mail: danziger@ts.astro.it

Received: 28 October 2004
Accepted: 21 February 2005

Abstract

By means of analytical calculations, we explore the self-enrichment scenario for Globular Cluster formation. According to this scenario, an initial burst of star formation occurs inside the core radius of the initial gaseous distribution. The outward-propagating shock wave sweeps up a shell in which gravitational instabilities may arise, leading to the formation of a second, metal-enriched, population of stars. We find a minimum mass of the proto-globular cluster of the order of 10⁶ . We also find that the observed spread in the magnitude–metallicity relation can be explained assuming cluster-to-cluster variations of some parameters like the thermalization efficiency, the mixing efficiency and the Initial Mass Function, as well as variations of the external pressure.