Concurrent formation of supermassive stars and globular clusters: Implications for early self-enrichment

Research output: Contribution to journalArticle


We present a model for the concurrent formation of globular clusters (GCs) and supermassive stars (SMSs, ≳103M) to address the origin of the HeCNONaMgAl abundance anomalies in GCs. GCs form in converging gas flows and accumulate low-angular momentum gas, which accretes on to protostars. This leads to an adiabatic contraction of the cluster and an increase of the stellar collision rate. A SMS can form via runaway collisions if the cluster reaches sufficiently high density before two-body relaxation halts the contraction. This condition is met if the number of stars ≳106 and the gas accretion rate ≳105M Myr-1, reminiscent of GC formation in high gas-density environments, such as - but not restricted to - the early Universe. The strong SMS wind mixes with the inflowing pristine gas, such that the protostars accrete diluted hot-hydrogen burning yields of the SMS. Because of continuous rejuvenation, the amount of processed material liberated by the SMS can be an order of magnitude higher than its maximum mass. This 'conveyor-belt' production of hot-hydrogen burning products provides a solution to the mass budget problem that plagues other scenarios. Additionally, the liberated material is mildly enriched in helium and relatively rich in other hot-hydrogen burning products, in agreement with abundances of GCs today. Finally, we find a super-linear scaling between the amount of processed material and cluster mass, providing an explanation for the observed increase of the fraction of processed material with GC mass. We discuss open questions of this new GC enrichment scenario and propose observational tests.


  • Mark Gieles
  • Corinne Charbonnel
  • Martin G.H. Krause
  • Vincent Hénault-Brunet
  • Oscar Agertz
  • Henny J.G.L.M. Lamers
  • Nathan Bastian
  • Alessia Gualandris
  • Alice Zocchi
  • James A. Petts
External organisations
  • University of Surrey
  • University of Geneva
  • University of Toulouse
  • University of Hertfordshire
  • National Research Council of Canada
  • Radboud University Nijmegen
  • University of Amsterdam
  • Liverpool John Moores University
  • St. Orsola-Malpighi University Hospital
  • European Space Research and Technology Centre (ESA/ESTEC)
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Astronomy, Astrophysics and Cosmology


  • Galaxies: star clusters: general, Globular clusters: general, Stars: abundances, Stars: black holes, Stars: kinematics and dynamics, Supergiants
Original languageEnglish
Pages (from-to)2461-2479
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 2018 Aug 1
Publication categoryResearch