The Origin of the Gaussian Initial Mass Function of Old Globular Cluster Systems

Abstract

[Abridged] Evidence favouring a Gaussian initial globular cluster mass function has accumulated over recent years. We show that an approximately Gaussian mass function is naturally generated from a power-law mass distribution of protoglobular clouds by expulsion from the protocluster of star forming gas due to supernova activity, provided that the power-law mass distribution shows a lower-mass limit. As a result of gas loss, the gravitational potential of the protocluster gets weaker and only a fraction of the newly formed stars is retained. The mass fraction of bound stars ranges from zero to unity, depending on the local star formation efficiency $\epsilon$. Assuming that $\epsilon$ is independent of the protoglobular cloud mass, we investigate how such variations affect the mapping of a protoglobular cloud mass function to the resulting globular cluster initial mass function. A truncated power-law cloud mass spectrum generates bell-shaped cluster initial mass functions, with a turnover location mostly sensitive to the lower limit of the cloud mass range. We also show that a Gaussian mass function for the protoglobular clouds with a mean $\log m_G\simeq 6.1-6.2$ and a standard deviation $\sigma \lesssim 0.4$ provides results very similar to those resulting from a truncated power-law cloud mass spectrum, that is, the distribution function of masses of protoglobular clouds influences only weakly the shape of the resulting globular star cluster initial mass function. The gas removal process and the protoglobular cloud mass-scale dominate the relevant physics. Moreover, gas removal during star formation in massive clouds is likely the prime cause of the predominance of field stars in the Galactic halo.

24 pages, accepted for publication in MNRAS

References in corpus (3)

• Gas expulsion and the destruction of massive young clusters
• Star cluster disruption by giant molecular clouds
• Number ratios of young stellar objects in embedded clusters

Cited by in corpus (16)

• The influence of residual gas expulsion on the evolution of the Galactic globular cluster system and the origin of the Population II halo
• Dense Stellar Populations: Initial Conditions
• The shape of the initial cluster mass function: what it tells us about the local star formation efficiency
• Impact of a star formation efficiency profile on the evolution of open clusters
• Erosion of Globular Cluster Systems: The Influence of Radial Anisotropy, Central Black Holes and Dynamical Friction
• The poorly constrained cluster disruption time-scale in the Large Magellanic Cloud
• Pre-supernova feedback sets the star cluster mass function to a power law and reduces the cluster formation efficiency
• Dynamical Constraints on the Origin of Multiple Stellar Populations in Globular Clusters
• Evolution of star cluster systems in isolated galaxies: first results from direct $N$-body simulations
• When efficient star formation drives cluster formation
• Open cluster stability and the effects of binary stars
• Dynamical evolution of the mass function and radial profile of the Galactic globular cluster system
• Photometric and Structural Parameters of Newly Discovered Nuclear Star Clusters in Local Volume Galaxies
• On the origin of the Schechter-like mass function of young star clusters in disk galaxies
• Reconstructing the initial mass function of disc-bulge Galactic globular clusters from N-body simulations
• The formation, disruption and properties of pressure-supported stellar systems and implications for the astrophysics of galaxies