A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 at z = 0.975

Observing the assembly of a massive system^⋆

¹ Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
e-mail: rfassben@mpe.mpg.de
² INAF - Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
³ CEASaclay, Service d’Astrophysique, L’Orme des Merisiers, Bât. 709, 91191 Gif-sur-Yvette Cedex, France
⁴ Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁵ University Observatory Munich, Ludwigs-Maximillians University Munich, Scheinerstr. 1, 81679 Munich, Germany
⁶ European Southern Observatory (ESO), Karl-Scharzschild-Str. 2, 85748 Garching, Germany
⁷ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
⁸ Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany

Received: 13 June 2010
Accepted: 29 August 2010

Abstract

Context. Observations of the formation and evolution of massive galaxy clusters and their matter components provide crucial constraints on cosmic structure formation, the thermal history of the intracluster medium (ICM), galaxy evolution, transformation processes, and gravitational and hydrodynamic interaction physics of the subcomponents.

Aims. We characterize the global multi-wavelength properties of the X-ray selected galaxy cluster XMMU J1230.3+1339 at z = 0.975, a new system discovered within the XMM-Newton Distant Cluster Project (XDCP). We measure and compare various widely used mass proxies and identify multiple cluster-associated components from the inner core region out to the large-scale structure environment.

Methods. We present a comprehensive galaxy cluster study based on a joint analysis of X-ray data, optical imaging and spectroscopy observations, weak lensing results, and radio properties for achieving a detailed multi-component view on a system at z ~ 1.

Results. We find an optically very rich and massive system with M₂₀₀ ≃ (4.2 ± 0.8)  ×  10¹⁴   M_⊙,  keV, and   ×  10⁴⁴ erg s^-1. We have identified a central fly-through group close to core passage and find marginally extended 1.4 GHz radio emission possibly associated with the turbulent wake region of the merging event. On the cluster outskirts we see evidence for an on-axis infalling group with a second brightest cluster galaxy (BCG) and indications for an additional off-axis group accretion event. We trace two galaxy filaments beyond the nominal cluster radius and provide a tentative reconstruction of the 3D-accretion geometry of the system.

Conclusions. In terms of total mass, ICM structure, optical richness, and the presence of two dominant BCG-type galaxies, the newly confirmed cluster XMMU J1230.3+1339 is likely the progenitor of a system very similar to the local Coma cluster, differing by 7.6 Gyr of structure evolution. This new system is an ideally suited astrophysical model laboratory for in-depth follow-up studies on the aggregation of baryons in the cold and hot phases.