H. Quintana

Discovery of a massive X-ray luminous galaxy cluster at z = 1.579

We report on the discovery of a very distant galaxy cluster serendipitously detected in the archive of the XMM-Newton mission, within the scope of the XMM-Newton Distant Cluster Project (XDCP). XMMUJ0044.0-2033 was detected at a high significance level (5σ) as a compact, but significantly extended source in the X-ray data, with a soft-band flux f (r 1.6.

The X-ray luminous galaxy cluster XMMU J1007.4+1237 at z = 1.56 - the dawn of starburst activity in cluster cores

Context. Observational galaxy cluster studies at z > 1.5 probe the formation of the first massive M > 10 14 M ⊙ dark matter halos, the early thermal history of the hot ICM, and the emergence of the red-sequence population of quenched early-type galaxies. Aims. We present first results for the newly discovered X-ray luminous galaxy cluster XMMUJ1007.4+1237 at z = 1.555, detected and confirmed by the XMM-Newton Distant Cluster Project (XDCP) survey. Methods. We selected the system as a serendipitous weak extended X-ray source in XMM-Newton archival data and followed it up with two-band near-infrared imaging and deep optical spectroscopy. Results. We can establish XMMU J 1007.4+1237 as a spectroscopically confirmed, massive, bona fide galaxy cluster with a bolometric X-ray luminosity of L bol X,500 ≃ (2.1 ± 0.4) x 10 44 erg/s, a red galaxy population centered on the X-ray emission, and a central radio-loud brightest cluster galaxy. However, we see evidence for the first time that the massive end of the galaxy population and the cluster red-sequence are not yet fully in place. In particular, we find ongoing starburst activity for the third ranked galaxy close to the center and another slightly fainter object. Conclusions. At a lookback time of 9.4 Gyr, the cluster galaxy population appears to be caught in an important evolutionary phase, prior to full star-formation quenching and mass assembly in the core region. X-ray selection techniques are an efficient means of identifying and probing the most distant clusters without any prior assumptions about their galaxy content.

A candidate tidal disruption event in the galaxy cluster Abell 3571

Context. Tidal disruption events are possible sources of temporary nuclear activity in galactic nuclei and can be considered as good indicators of the existence of supermassive black holes in the centers of galaxies. Aims. A new X-ray source has been detected serendipitously with ROSAT in a PSPC pointed observation of the galaxy clusterxa0A3571. Given the strong flux decay of the object in subsequent detections, the tidal disruption scenario is investigated as a possible explanation of the event. Methods. We followed the evolution of the X-ray transient with ROSAT, XMM-Newton and Chandra for a total period of ~13xa0years. We also obtained 7-band optical/NIRxa0photometry with GROND at the ESO/MPI 2.2xa0m telescope. Results. We report a very large decay of the X-ray flux of the ROSAT source identified with the galaxy LEDAxa0095953, a member of the cluster Abellxa03571. We measured a maximum 0.3-2.4xa0keV luminosity Logu2009( L X )xa0= 42.8xa0ergxa0s -1 . The high state of the source lasted at least 150xa0ks; afterwards L X declined as ~ t -2 . The spectrum of the brightest epoch is consistent with a black body with temperature

The Shapley Supercluster. II. Spectroscopic Observations in a Wide Area and General Morphology

kTsim

The Shapley Supercluster. III. Collapse Dynamics and Mass of the Central Concentration

0.12xa0keV. Conclusions. The total energy released by this event in 10xa0yr was estimated to be

A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 at z = 0.975 - Observing the assembly of a massive system

Delta~E

First simultaneous optical/near-infrared imaging of an X-ray selected, high-redshift cluster of galaxies with GROND - The galaxy population of XMMU J0338.7 + 0030 at z = 1.1

xa0> 2xa0

Identification and study of systems of galaxies in the Shapley supercluster

times

Redshifts in the Southern Abell Redshift Survey Clusters. I. The Data

10 50 xa0erg. We interpret this event as a tidal disruption of a solar type star by the central supermassive black hole (i.e.xa0~10

Exploring the galaxy cluster-group transition regime at high redshifts - physical properties of two newly detected z > 1 systems

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