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Creation of cosmic structure in the complex galaxy cluster merger Abell 2744

Merten, J.; Coe, D.; Dupke, R.; Massey, R.; Zitrin, A.; Cypriano, E.S.; Okabe, N.; Frye, B.; Braglia, F.G.; Jiménez-Teja, Y.; Benítez, N.; Broadhurst, T.; Rhodes, J.; Meneghetti, M.; Moustakas, L.A.; Sodré Jr., L.; Krick, J.; Bregman, J.N.

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J. Merten

D. Coe

R. Dupke

A. Zitrin

E.S. Cypriano

N. Okabe

B. Frye

F.G. Braglia

Y. Jiménez-Teja

N. Benítez

T. Broadhurst

J. Rhodes

M. Meneghetti

L.A. Moustakas

L. Sodré Jr.

J. Krick

J.N. Bregman


We present a detailed strong-lensing, weak-lensing and X-ray analysis of Abell 2744 (z= 0.308), one of the most actively merging galaxy clusters known. It appears to have unleashed ‘dark’, ‘ghost’, ‘bullet’ and ‘stripped’ substructures, each ∼1014 M⊙. The phenomenology is complex and will present a challenge for numerical simulations to reproduce. With new, multiband Hubble Space Telescope (HST) imaging, we identify 34 strongly lensed images of 11 galaxies around the massive Southern ‘core’. Combining this with weak-lensing data from HST, VLT and Subaru, we produce the most detailed mass map of this cluster to date. We also perform an independent analysis of archival Chandra X-ray imaging. Our analyses support a recent claim that the Southern core and Northwestern substructure are post-merger and exhibit morphology similar to the Bullet Cluster viewed from an angle. From the separation between X-ray emitting gas and lensing mass in the Southern core, we derive a new and independent constraint on the self-interaction cross-section of dark matter particles σ/m < 3 ± 1 cm2 g−1. In the Northwestern substructure, the gas, dark matter and galaxy components have become separated by much larger distances. Most curiously, the ‘ghost’ clump (primarily gas) leads the ‘dark’ clump (primarily dark matter) by more than 150 kpc. We propose an enhanced ‘ram-pressure slingshot’ scenario which may have yielded this reversal of components with such a large separation, but needs further confirmation by follow-up observations and numerical simulations. A secondary merger involves a second ‘bullet’ clump in the North and an extremely ‘stripped’ clump to the West. The latter appears to exhibit the largest separation between dark matter and X-ray emitting baryons detected to date in our sky.


Merten, J., Coe, D., Dupke, R., Massey, R., Zitrin, A., Cypriano, E., …Bregman, J. (2011). Creation of cosmic structure in the complex galaxy cluster merger Abell 2744. Monthly Notices of the Royal Astronomical Society, 417(1), 333-347.

Journal Article Type Article
Publication Date Oct 11, 2011
Deposit Date Mar 21, 2013
Publicly Available Date Feb 19, 2015
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 417
Issue 1
Pages 333-347
Keywords Gravitational lensing: strong, Gravitational lensing: weak, Galaxies: clusters: individual: Abell 2744, Dark matter, Large-scale structure of Universe, X-rays: individual: Abell 2744.


Published Journal Article (8.6 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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