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From the top down and back up again: star cluster structure from hierarchical star formation

Grudić, Michael Y. and Guszejnov, Dávid and Hopkins, Philip F. and Lamberts, Astrid and Boylan-Kolchin, Michael and Murray, Norman and Schmitz, Denise (2018) From the top down and back up again: star cluster structure from hierarchical star formation. Monthly Notices of the Royal Astronomical Society, 481 (1). pp. 688-702. ISSN 0035-8711. PMCID PMC6296242. doi:10.1093/mnras/sty2303.

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Young massive star clusters spanning ∼10^4--10^8 M_⊙ in mass have been observed to have similar surface brightness profiles. We show that recent hydrodynamical simulations of star cluster formation have also produced star clusters with this structure. We argue analytically that this type of mass distribution arises naturally in the relaxation from a hierarchically clustered distribution of stars into a monolithic star cluster through hierarchical merging. We show that initial profiles of finite maximum density will tend to produce successively shallower power-law profiles under hierarchical merging, owing to certain conservation constraints on the phase-space distribution. We perform N-body simulations of a pairwise merger of model star clusters and find that mergers readily produce the shallow surface brightness profiles observed in young massive clusters. Finally, we simulate the relaxation of a hierarchically clustered mass distribution constructed from an idealized fragmentation model. Assuming only power-law spatial and kinematic scaling relations, these numerical experiments are able to reproduce the surface density profiles of observed young massive star clusters. Thus, we bolster the physical motivation for the structure of young massive clusters within the paradigm of hierarchical star formation. This could have important implications for the structure and dynamics of nascent globular clusters.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle Paper
Grudić, Michael Y.0000-0002-1655-5604
Guszejnov, Dávid0000-0001-5541-3150
Hopkins, Philip F.0000-0003-3729-1684
Lamberts, Astrid0000-0001-8740-0127
Boylan-Kolchin, Michael0000-0002-9604-343X
Schmitz, Denise0000-0001-6297-9312
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 August 20. Received 2018 August 20; in original form 2017 August 27. We thank Michael S. Fall, Bruce Elmegreen, Scott Tremaine, and the anonymous referee for helpful feedback. Support for MG and TAPIR co-authors was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. MB-K acknowledges support from NSF grant AST-1517226 and from NASA grants NNX17AG29G and HST-AR-13888, HST-AR-13896, and HST-AR-14282 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Numerical calculations were run on the Caltech compute clusters ‘Zwicky’ (NSF MRI award # PHY-0960291) and ‘Wheeler’ and allocation TG-AST130039 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the NSF.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:stars: formation, galaxies: star clusters: general, galaxies: star formation
Issue or Number:1
PubMed Central ID:PMC6296242
Record Number:CaltechAUTHORS:20181129-111459057
Persistent URL:
Official Citation:Michael Y Grudić, Dávid Guszejnov, Philip F Hopkins, Astrid Lamberts, Michael Boylan-Kolchin, Norman Murray, Denise Schmitz; From the top down and back up again: star cluster structure from hierarchical star formation, Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 1, 21 November 2018, Pages 688–702,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91330
Deposited By: George Porter
Deposited On:29 Nov 2018 19:23
Last Modified:17 Feb 2022 00:16

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