First supernovae in Galactic globular clusters

Abstract

We address the question of whether globular clusters (GC) in a protogalaxy could evolve chemically for some time as isolated systems, enriching themselves with heavy elements produced in the first supernova events that follow initial star formation. We determine both the critical mass of a protoglobular cluster (proto‐GC) that is needed to retain the ejecta of the very first supernova, and the critical energy (i.e. number of supernovae) that is needed to expel the residual gas from a cluster of a given mass. We show that the critical mass of a proto‐GC for a wide range of parameters (size, degree of fragmentation, degree of central concentration) does not exceed to 106 M⊙. The critical star formation efficiency (resulting in a certain number of supernova events) that is needed to expel the residual gas is about 1–3 per cent. Assuming that all the star‐forming activity in the cluster stops after the critical number of supernovae have exploded, we reproduce the basic parameters of the present‐day globular clusters, i.e. their final masses and oxygen abundances. A typical globular cluster in our model originates from a cloud with a mass of to 108 M⊙. When all the remaining gas is lost from the cluster, its mass is about a few times 105 M⊙. A significant fraction (∼97 per cent) of an initial protocluster cloud is then available for galactic disc formation. We check our results with the method that is usually applied to elliptical galaxy modelling. The assumption that a protocluster cloud evolves and accumulates metals until the gas thermal energy (increased due to supernova explosions) exceeds its binding energy leads to the same conclusions. We also comment on the observed homogeneity of the iron distribution in globular clusters, which is often considered as a primary argument against self‐enrichment. According to the current paradigm, iron originates mainly in Type Ia supernovae with long‐lived progenitors. If one states that iron has existed in globular clusters prior to their formation, it should have had a pre‐Galactic origin. We argue that it is hard to reconcile this with the observed correlation of average iron abundances in extragalactic GC systems with the luminosities of parent galaxies.

Three‐dimensional Numerical Simulations of Thermal‐Gravitational Instability in the Protogalactic Halo Environment

“…It is because we can not rule out the possibility that the clouds may be able to lose most, say ∼ 99%, of their angular momentum, while they collapse and lose ∼ 90% of their mass. For instance, in the so-called self-enrichment model of globular cluster formation, first generation Type II supernovae govern star formation and the removal of residual gas (e.g., see Parmentier et al 1999;Shustov & Wiebe 2000). In this model the star formation may have occurred preferentially at the core, and most gas in the outskirt with large angular momentum may have been blown out.…”

A search for radio supernovae and supernova remnants in the region of NGC 1569's super star clusters

“…Besides the statistical argument brought forward to explain the absence of short-lived RSNe and RSNs in and near the SSCs, we believe that there exists also a valid kinematical argument for their absence. When extrapolating to SSCs Canto et al's (2000) calculation of the action of stellar winds of many massive stars in a cluster, combined with the action of several SN explosions, and when considering the influence of the cluster gravitational field on the propagation of the SN blast in a similar way as done for proto globular clusters (Shustov & Wiebe 2000), a violent and turbulent outflow of hot material is expected to occur which leaves little room for a quiescent development of SNRs. Using the radius r(A) and mass M(A) of the SSC-A mentioned above, the stellar mass concentration ρ and the average distance <δ> between the cluster stars is…”

Self-enrichment in globular clusters

“…The pioneers in this kind of study have been Dopita & Smith (1986) and Cayrel (1986), but many other authors have studied the subject (Morgan & Lake 1989;Ikuta & Arimoto 2000; among others). In particular, Shustov & Wiebe (2000; hereafter SW00) and Parmentier et al (1999;hereafter P99) addressed the question of how massive a PGC should be in order to retain the products of at least one supernova (SN) and how many SNe can a PGC sustain before being disrupted as a result of the injected energy. P99 tried also to compare the results of their model with the magnitude-metallicity relation in a particular sample of Milky Way GCs (namely the older ones).…”