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Formation of the Galactic globular clusters with He-rich stars in low-mass haloes virialized at high redshift

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posted on 2024-07-11, 11:28 authored by Kenji Bekki, Hideki Yahagi, Masahiro Nagashima, Duncan ForbesDuncan Forbes
Recent observations have reported that the Galactic globular clusters (GCs) with unusually extended horizontal-branch (EHB) morphologies show a significantly lower velocity dispersion compared with that of the entire Galactic GC system. We consider that the observed distinctive kinematics of GCs with EHB has valuable information on the formation epochs of GCs and accordingly discuss this observational result based on cosmological N-body simulations with a model of GC formation. We assume that GCs in galaxies were initially formed in low-mass haloes at high redshifts and we investigate final kinematics of GCs in their host haloes at z= 0. We find that GCs formed in haloes virialized at z > 10 show lower velocity dispersions on average than those formed at z > 6 for haloes with GCs at z= 0. We thus suggest that the origin of the observed lower velocity dispersion for the Galactic GCs with EHBs is closely associated with earlier formation epochs (z > 10) of haloes initially hosting the GCs in the course of the Galaxy formation. Considering that the origin of EHBs can be due to the presence of helium-enhanced second-generation stars in GCs, we discuss the long-standing second parameter problem of GCs in the context of different degrees of chemical pollution in GC-forming gas clouds within low-mass haloes virialized at different redshifts.

Funding

Fujitsu (Japan)

Japan Society for the Promotion of Science

Australian Research Council

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PDF (Accepted manuscript)

ISSN

1745-3933

Journal title

Monthly Notices of the Royal Astronomical Society: Letters

Volume

382

Issue

1

Pagination

l87-l91

Publisher

Wiley

Copyright statement

Copyright © 2007 Royal Astronomical Society. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher.

Language

eng

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