Letter to the Editor
Indications for 3 Mpc-scale large-scale structure associated with an X-ray luminous cluster of galaxies at z = 0.95*
1
Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany e-mail: rfassben@mpe.mpg.de
2
Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
3
University of Michigan, Department of Astronomy, 918 Dennison Building, Ann Arbor, MI 48109-1090, USA
4
European Southern Observatory (ESO), Karl-Scharzschild-Str. 2, 85748 Garching, Germany
Received:
5
November
2007
Accepted:
24
January
2008
Context. X-ray luminous clusters of galaxies at z ~ 1 are emerging as major cosmological probes and are fundamental tools to study the cosmic large-scale structure and environmental effects of galaxy evolution at large look-back times.
Aims. We present details of the newly-discovered galaxy cluster XMMU J0104.4-0630 at z = 0.947 and a probable associated system in the LSS environment.
Methods. The clusters were found in a systematic study for high-redshift systems using deep archival XMM-Newton data for the serendipitous detection and the X-ray analysis, complemented by optical/near-infrared (NIR) imaging observations and spectroscopy of the main cluster.
Results. We find a well-evolved, intermediate luminosity cluster with 
erg s-1
and strong central 1.4 GHz radio emission.
The cluster galaxy population exhibits a pronounced transition toward bluer colors at cluster-centric distances of 1-2 core radii, consistent with an age difference of 1-2 Gyr for a single burst solar metallicity model.
The second, less evolved X-ray cluster at a projected distance of 6.4´ (~3 Mpc) and a concordant red-sequence color likely forms
a cluster-cluster bridge with the main target as part of its surrounding large-scale structure at z 
0.95.
Key words: galaxies: clusters: general / X-rays: galaxies: clusters / cosmology: large-scale structure of Universe / galaxies: elliptical and lenticular, cD / galaxies: evolution
Based on observations obtained with ESO Telescopes at the Paranal Observatory under programme ID 72.A-0706 and 275.A-5059, and observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).
© ESO, 2008