The realm of the Galactic globular clusters and the mass of their primordial clouds

Abstract

By adopting the empirical constraints related to the estimates of Helium enhancement ($\Delta Y$), present mass ratio between first and second stellar generations ($M_{1G}/M_{2G}$) and the actual mass of Galactic globular clusters ($M_{GC}$), we envisage a possible scenario for the formation of these stellar systems. Our approach allows for the possible loss of stars through evaporation or tidal interactions and different star formation efficiencies. In our approach the star formation efficiency of the first generation (${\epsilon }_{1G}$) is the central factor that links the stellar generations as it not only defines both the mass in stars of the first generation and the remaining mass available for further star formation, but it also fixes the amount of matter required to contaminate the second stellar generation. In this way, ${\epsilon }_{1G}$ is fully defined by the He enhancement between successive generations in a GC. We also show that globular clusters fit well within a $\Delta Y$ {\it vs} $M_{1G}/M_{2G}$ diagram which indicates three different evolutionary paths. The central one is for clusters that have not loss stars, through tidal interactions, from either of their stellar generations, and thus their present $M_{GC}$ value is identical to the amount of low mass stars ($M_{\ast }\le$ 1 M${}_{\odot }$) that resulted from both stellar generations. Other possible evolutions imply either the loss of first generation stars or the combination of a low star formation efficiency in the second stellar generation and/or a loss of stars from the second generation. From these considerations we derive a lower limit to the mass ($M_{tot}$) of the individual primordial clouds that gave origin to globular clusters.

17 pages, 2 figures, accepted for publication in the Astrophysical Journal

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Cited by in corpus (7)

• Globular Cluster Formation at High Density: A model for Elemental Enrichment with Fast Recycling of Massive-Star Debris
• Gas expulsion vs gas retention: what process dominates in young massive clusters?
• The formation of secondary stellar generations in massive young star clusters from rapidly cooling shocked stellar winds
• On the determination of the He abundance distribution in globular clusters from the width of the main sequence
• Ultraviolet Imaging Telescope (UVIT) observation of the Galactic Globular Cluster NGC 7492
• On the star formation efficiencies and evolution of multiple stellar generations in Globular Clusters
• The Formation of Globular Clusters as a Case of Overcooling