Journal Article

The double galaxy cluster Abell 2465 – I. Basic properties: optical imaging and spectroscopy

Gary A. Wegner

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 413, issue 2, pages 1333-1352
Published in print May 2011 | ISSN: 0035-8711
Published online April 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18218.x
The double galaxy cluster Abell 2465 – I. Basic properties: optical imaging and spectroscopy

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Optical imaging and spectroscopic observations of the z= 0.245 double galaxy cluster Abell 2465 are described. This object appears to be undergoing a major merger. It is a double X-ray source and is detected in the radio at 1.4 GHz. The purpose of this paper is to investigate signatures of the interaction of the two components. Redshifts were measured to determine velocity dispersions and virial radii of each component. The technique of fuzzy clustering was used to assign membership weights to the galaxies in each clump. Using redshifts of 93 cluster members within 1.4 Mpc of the subcluster centres, the virial masses of the north-east (NE) and south-west (SW) components are Mv= 4.1 ± 0.8 × 1014 and 3.8 ± 0.8 × 1014 M, respectively. These agree within the errors with masses from X-ray scaling relations. The projected velocity difference between the two subclusters is 205 ± 149 km s−1. The anisotropy parameter, β, is found to be low for both components. Spectra of 37 per cent of the spectroscopically observed galaxies show emission lines and are predominantly star forming in the diagnostic diagram. No strong active galactic nucleus sources were found. The emission-line galaxies tend to lie between the two cluster centres with more near the SW clump. The luminosity functions of the two subclusters differ. The NE component is similar to many rich clusters, while the SW component has more faint galaxies. The NE clump’s light profile follows a single Navarro–Frenk–White profile with c= 10 while the SW is better fitted with an extended outer region and a compact inner core, consistent with available X-ray data indicating that the SW clump has a cooling core. The observed differences and properties of the two components of Abell 2465 are interpreted to have been caused by a collision 2–4 Gyr ago, after which they have moved apart and are now near their apocentres, although the start of a merger remains a possibility. The number of emission-line galaxies gives weight to the idea that galaxy cluster collisions trigger star formation.

Keywords: galaxies: clusters: general; galaxies: clusters: individual: Abell 2465

Journal Article.  13230 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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