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New Chandra X-ray data and extensive optical spectroscopy, obtained with AAOmega on the 3.9 m Anglo-Australian Telescope, are used to study the complex merger taking place in the galaxy cluster Abell 2744. Combining our spectra with data…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Matt S. Owers , Scott W. Randall , Paul E. J. Nulsen , Warrick J. Couch , Laurence P. David , Joshua C. Kempner

We present results of a strong-lensing analysis of MACS J0717.5+3745 (hereafter MACS J0717), an extremely X-ray luminous galaxy cluster at z=0.55. Observations at different wavelengths reveal a complex and dynamically very active cluster,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 M. Limousin , H. Ebeling , J. Richard , A. M. Swinbank , G. P. Smith , M. Jauzac , S. Rodionov , C. -J. Ma , I. Smail , A. C. Edge , E. Jullo , J. P. Kneib

CIZA J2242.8+5301 is a merging system with a prominent (~2 Mpc long) radio relic, which together with the morphology of the X-ray emission provides strong evidence for a violent collision along the N-S axis. We present our constraints on…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-23 M. James Jee , Andra Stroe , William Dawson , David Wittman , Henk Hoekstra , Marcus Bruggen , Huub Rottggering , David Sobral , Reinout J. van Weeren

We present deep and high fidelity images of the merging galaxy cluster Abell 2256 at low frequencies, using the upgraded Giant Metrewave Radio Telescope (uGMRT) and LOw-Frequency ARray (LOFAR). This cluster hosts one of the most prominent…

The galaxy cluster PSZ2 G181.06+48.47 ($z=0.234$) is a post-merging system that exhibits symmetric double radio relics separated by ~2.7 Mpc. We present the first weak-lensing analysis of PSZ2 G181.06+48.47 and propose possible merging…

Cosmology and Nongalactic Astrophysics · Physics 2025-03-05 Eunmo Ahn , Hyejeon Cho , M. James Jee , Wonki Lee , Andra Stroe , Kamlesh Rajpurohit , Kyle Finner , William Forman , Christine Jones , Reinout van Weeren

We study the dynamical status of the poor, low X-ray luminous galaxy clusters Abell 610, Abell 725, and Abell 796 (at z=0.1, 0.09, and 0.16, respectively), containing diffuse radio sources (relic, relic, and possible halo, respectively).…

Astrophysics · Physics 2009-11-13 W. Boschin , R. Barrena , M. Girardi , M. Spolaor

The aim of the present work is to study the overall mass distribution of the galaxy clusters Abell 1351 and Abell 1995 using weak gravitational lensing. These clusters have got a very different mass structure and dynamical state, and are…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 K. Holhjem , M. Schirmer , H. Dahle

We analyze the dynamical state of Abell 1914, a merging cluster hosting a radio halo, quite unusual for its structure. Our study considers spectroscopic data for 119 galaxies obtained with the Italian Telescopio Nazionale Galileo. We select…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 R. Barrena , M. Girardi , W. Boschin

We present a detailed spatial and dynamical analysis of the central $\sim$~2.2~\h~Mpc region of the galaxy cluster Abell~521 (z=0.247), based on 238 spectra obtained at the 3.6~m Telescope of ESO and at the CFHT. From the analysis of the…

Astrophysics · Physics 2008-11-26 C. Ferrari , S. Maurogordato , A. Cappi , C. Benoist

The Bullet Cluster (1E 0657-56) is a key astrophysical laboratory for studying dark matter, galaxy cluster mergers, and shock propagation in extreme environments. Using new JWST imaging, we present the highest-resolution mass reconstruction…

Astrophysics of Galaxies · Physics 2025-07-08 Sangjun Cha , Boseong Young Cho , Hyungjin Joo , Wonki Lee , Kim HyeongHan , Zachary P. Scofield , Kyle Finner , M. James Jee

The largest galaxy clusters are observed still to be forming through major cluster-cluster mergers, often showing observational signatures such as radio relics and giant radio haloes. Using LOFAR Two-meter Sky Survey data, we present new…

Abell 2146 ($z$ = 0.232) consists of two galaxy clusters undergoing a major merger. The system was discovered in previous work, where two large shock fronts were detected using the $\textit{Chandra X-ray Observatory}$, consistent with a…

We analyze the internal structures of clusters A1689 and A2218 by applying a recent development of the method of wavelet analysis, which uses the complete information obtained from optical data, i.e. galaxy positions and redshifts. We find…

Astrophysics · Physics 2008-11-26 M. Girardi , D. Fadda , E. Escalera , G. Giuricin , F. Mardirossian , M. Mezzetti

Diffuse, low surface-brightness radio emission in merging galaxy clusters provides insights into cosmic structure formation, the growth of magnetic fields, and turbulence. This paper reports a search for diffuse radio emission in a pilot…

We analyze a rich dataset including Subaru/SuprimeCam, HST/ACS and WFC3, Keck/DEIMOS, Chandra/ACIS-I, and JVLA/C and D array for the merging galaxy cluster ZwCl 0008.8+5215. With a joint Subaru/HST weak gravitational lensing analysis, we…

Astrophysics of Galaxies · Physics 2017-04-05 Nathan Golovich , Reinout J. van Weeren , William A. Dawson , M. James Jee , David Wittman

Structure formation is thought to act via hierarchical mergers and accretion of smaller systems driven by gravity with dark matter dominating the gravitational field. Combining X-ray and optical imaging and spectroscopy provides a powerful…

Cosmology and Nongalactic Astrophysics · Physics 2012-04-11 F. Ziparo , F. G. Braglia , D. Pierini , A. Finoguenov , H. Boehringer , A. Bongiorno

We present new, high frequency radio observations of the merging galaxy clusters PLCK G287.0+32.9, Abell 2744, and Bullet. These clusters are known to host $\sim$Mpc scale sources, known as radio halos, which are formed by the acceleration…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-20 K. Rajpurohit , A. Botteon , E. O'Sullivan , W. Forman , M. Balboni , L. Bruno , R. J. van Weeren , M. Hoeft , G. Brunetti , C. Jones , A. S. Rajpurohit , S. P. Sikhosana

The frequently observed association between giant radio halos and merging galaxy clusters has driven present theoretical models of non-thermal emission from galaxy clusters, which are based on the idea that the energy dissipated during…

Cosmology and Nongalactic Astrophysics · Physics 2010-11-09 R. Cassano , S. Ettori , S. Giacintucci , G. Brunetti , M. Markevitch , T. Venturi , M. Gitti

The relation between giant radio halos and mini-halos in galaxy clusters is not understood. The former are usually associated with merging clusters, the latter are found in relaxed systems. In the last years, the advent of low-frequency…

The rich cluster Abell 520 (z=0.201) exhibits truly extreme and puzzling multi-wavelength characteristics. It may best be described as a "cosmic train wreck." It is a major merger showing abundant evidence for ram pressure stripping, with a…

Astrophysics · Physics 2009-11-13 A. Mahdavi , H. Hoekstra , A. Babul , D. Balam , P. Capak
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