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Morphology of low-redshift compact galaxy clusters -- I. Shapes and radial profiles

Strazzullo, V. and Paolillo, M. and Longo, G. and Puddu, E. and Djorgovski, S. G. and de Carvalho, R. R. and Gal, R. R. (2005) Morphology of low-redshift compact galaxy clusters -- I. Shapes and radial profiles. Monthly Notices of the Royal Astronomical Society, 359 (1). pp. 191-210. ISSN 0035-8711. doi:10.1111/j.1365-2966.2005.08880.x.

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The morphology of clusters of galaxies may be described with a set of parameters which contain information concerning the formation and evolutionary history of these systems. In this paper we present a preliminary study of the morphological parameters of a sample of 28 compact Abell clusters extracted from Digitized Palomar Sky Survey data, measured with a procedure based on the use of the CIAO-SHERPA software, developed at the Centre for Astrophysics for X-ray data analysis. The morphology of galaxy clusters is parametrized by their apparent ellipticity, position angle of the major axis, centre coordinates, core radius and β-model power-law index. Our procedure provides estimates of these parameters (and of the related uncertainties) by simultaneously fitting them all, overcoming some of the difficulties induced by sparse data and low-number statistics typical of this kind of analysis. The cluster parameters were fitted in a 6 × 6 Mpc^2 region, measuring the background in a 4 < R < 5 Mpc annulus. We also explore the correlations between shape and profile parameters and other cluster properties. Our results can be summarized as follows: one-third of this compact cluster sample has core radii smaller than 100 kpc, i.e. near the limit that our data allow us to resolve, possibly consistent with cusped models. The remaining clusters span a broad range of core radii up to ∼1500 kpc, including some apparently regular clusters with well-resolved core radii. More than 80 per cent of this sample has ellipticity higher than 0.2. The alignment between the cluster and the major axis of the dominant galaxy is confirmed at a high significance level, while no correlation is observed with other bright cluster members. No significant correlation is found between cluster richness and ellipticity. Instead, cluster richness is found to correlate, albeit with large scatter, with the cluster core radius. Finally, in contrast to claims in previous works, a flat universe seems to be favoured, and in any case is not excluded, by the power-law index β of our number density profiles.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Paolillo, M.0000-0003-4210-7693
Longo, G.0000-0002-9182-8414
Djorgovski, S. G.0000-0002-0603-3087
de Carvalho, R. R.0000-0002-1283-3363
Additional Information:© 2005 RAS. Accepted 2005 January 28. Received 2005 January 27; in original form 2004 September 7. Published: 01 May 2005. The authors wish to thank Andrea Biviano, together with Christophe Adami, for kindly providing us with his code at the beginning of this study and for several helpful suggestions on its use. We also thank Elisabetta De Filippis for many useful discussions. VS acknowledges helpful discussions with Gabriella De Lucia, Maurilio Pannella and Paola Popesso. We thank the referee for very helpful and constructive comments. VS warmly thanks Massimo Capaccioli for assistance and hospitality at the Osservatorio Astronomico di Capodimonte, and is grateful to Ralf Bender and all his group for hospitality at MPE during part of this work. This work was partly funded by the Italian Ministry of Research through a COFIN grant and by the European Social Fund (FSE) through a PhD grant. Processing and cataloguing of DPOSS was supported by a generous grant from the Norris Foundation and by other private donors. This research has made use of the X-rays Clusters Data base (BAX) which is operated by the Laboratoire d'Astrophysique de Tarbes-Toulouse (LATT), under contract with the Centre National d'Etudes Spatiales (CNES).
Funding AgencyGrant Number
Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)UNSPECIFIED
European Social FundUNSPECIFIED
Norris FoundationUNSPECIFIED
Centre National d'Etudes Spatiales (CNES)UNSPECIFIED
Subject Keywords:galaxies: clusters: general – galaxies: clusters: individual – cosmology: observations
Issue or Number:1
Record Number:CaltechAUTHORS:20190722-133357882
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Official Citation:V. Strazzullo, M. Paolillo, G. Longo, E. Puddu, S. G. Djorgovski, R. R. De Carvalho, R. R. Gal, Morphology of low-redshift compact galaxy clusters — I. Shapes and radial profiles, Monthly Notices of the Royal Astronomical Society, Volume 359, Issue 1, 1 May 2005, Pages 191–210,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97328
Deposited By: Tony Diaz
Deposited On:22 Jul 2019 20:40
Last Modified:16 Nov 2021 17:30

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