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Connecting Substructure in Galaxy Cluster Cores at z = 0.2 with Cluster Assembly Histories

Smith, Graham P. and Taylor, James E. (2008) Connecting Substructure in Galaxy Cluster Cores at z = 0.2 with Cluster Assembly Histories. Astrophysical Journal Letters, 682 (2). L73-L76. ISSN 2041-8205. doi:10.1086/591271.

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We use semianalytic models of structure formation to interpret gravitational lensing measurements of substructure in galaxy cluster cores (R ≤ 250 h^(−1) kpc) at z = 0.2. The dynamic range of the lensing-based substructure fraction measurements is well matched to the theoretical predictions, both spanning ƒ_(sub) ~ 0.05–0.65. The structure formation model predicts that ƒ_(sub) is correlated with cluster assembly history. We use simple fitting formulae to parameterize the predicted correlations: Δ_(90) = τ_(90) + α_(90)log (ƒ_(sub)) and Δ_(50) = τ_(50) + α_(50)log (ƒ_(sub)) , where Δ_(90) and Δ_(50) are the predicted lookback times from z = 0.2 to when each theoretical cluster had acquired 90% and 50%, respectively, of the mass it had at z = 0.2. The best-fit parameter values are α_(90) = − 1.34 ± 0.79 Gyr , τ_(90) = 0.31 ± 0.56 Gyr and α_(50) = − 2.77 ± 1.66 Gyr , τ_(50) = 0.99 ± 1.18 Gyr . Therefore, (1) observed clusters with ƒ_(sub)≾ 0.1 (e.g., A383, A1835) are interpreted, on average, to have formed at z ≳ 0.8 and to have suffered ≤10% mass growth since z ≃ 0.4, and (2) observed clusters with f_(sub)≳ 0.4 (e.g., A68, A773) are interpreted as, on average, forming since z ≃ 0.4 and suffering >10% mass growth in the ~500 Myr preceding z = 0.2, i.e., since z = 0.25. In summary, observational measurements of ƒ_(sub) can be combined with structure formation models to estimate the age and assembly history of observed clusters. The ability to "age date" approximately clusters in this way has numerous applications to the large samples of clusters that are becoming available.

Item Type:Article
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Smith, Graham P.0000-0003-4494-8277
Additional Information:© 2008. The American Astronomical Society. Received 2008 April 25; accepted 2008 June 24; published 2008 July 8. We thank Arif Babul, Habib Khosroshahi, Jean-Paul Kneib, Ian Smail, and Risa Wechsler for helpful discussions. G. P. S. acknowledges support from NASA (HST-GO-10420.04-A), Caltech, and a Royal Society University Research Fellowship. J. E. T. acknowledges financial support from the US NSF (grant AST-0307859) and DoE (contract DE-FG02-04ER41316) and from NSERC Canada.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-04ER41316
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:cosmology; observations cosmology; theory galaxies; clusters; general galaxies; clusters; individual (A68, A209, A267, A383, A773, A963, A1763, A1835, A2218, A2219) gravitational lensing
Issue or Number:2
Record Number:CaltechAUTHORS:20090610-105508899
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Official Citation:Connecting Substructure in Galaxy Cluster Cores at z = 0.2 with Cluster Assembly Histories Graham P. Smith and James E. Taylor 2008 ApJ 682 L73-L76 doi: 10.1086/591271
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14389
Deposited By: Ruth Sustaita
Deposited On:01 Sep 2009 16:16
Last Modified:08 Nov 2021 23:11

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