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

Gieles, Mark, Charbonnel, C, Krause, M, Hénault-Brunet, V, Agertz, Oscar, Lamers, H, Bastian, N, Gualandris, Alessia, Zocchi, A and Petts, James (2018) Concurrent formation of supermassive stars and globular clusters: implications for early self-enrichment Monthly Notices of the Royal Astronomical Society, 478 (2), sty1059. pp. 2461-2479.

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Abstract

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 onto 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, 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.

Item Type:	Article
Divisions :	Faculty of Engineering and Physical Sciences > Physics
Authors :	Name Email ORCID Gieles, Mark m.gieles@surrey.ac.uk Charbonnel, C Krause, M Hénault-Brunet, V Agertz, Oscar o.agertz@surrey.ac.uk Lamers, H Bastian, N Gualandris, Alessia a.gualandris@surrey.ac.uk Zocchi, A Petts, James j.petts@surrey.ac.uk
Date :	26 April 2018
DOI :	10.1093/mnras/sty1059
Copyright Disclaimer :	© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society, Main Journal, following peer review. The version of record: 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; Concurrent formation of supermassive stars and globular clusters: implications for early self-enrichment, Monthly Notices of the Royal Astronomical Society, sty1059, https://doi.org/10.1093/mnras/sty1059 is available online at: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/sty1059/4987226
Uncontrolled Keywords :	galaxies: star clusters: general globular clusters: general – stars: kinematics and dynamics – stars: abundances – stars: supergiants – stars: black holes
Depositing User :	Melanie Hughes
Date Deposited :	27 Apr 2018 16:03
Last Modified :	24 Jul 2018 14:37
URI:	http://epubs.surrey.ac.uk/id/eprint/846325

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