The ROSAT deep survey. VII. RX J105343+5735: A massive cluster at z = 1.263

Creators: Thompson, D.; Pozzetti, L.; Hasinger, G.; Lehmann, I.; Schmidt, M.; Soifer, B. T.; Szokoly, G.; Wilson, G.; Zamorani, G.

Abstract

The eastern lobe of the unusual double-lobed extended X-ray source RX J105343+5735 is confirmed to be a massive cluster at high redshift. Deep optical and near-infrared imaging show an overdensity of galaxies in both X-ray lobes, including a significant excess of red galaxies (R – K > 5.3) with colors typical of elliptical galaxies at z > 1. We have used new photometry to place better constraints on the redshifts of the cluster galaxies. A Keck NIRSPEC spectrum of one of the bright central galaxies in the eastern lobe shows a narrow Hα emission line at 1.485 microns, yielding a redshift of 1.263. The [OII] λ3727 Å line from the gravitationally lensed arc is also detected, giving a redshift of 2.577 for the lensed galaxy and confirming prior measurements. The improbability of chance alignment and similarity of colors for the galaxies in the two X-ray lobes are consistent with the western lobe also being at z = 1.26. The system may thus represent a pair of clusters in the process of merging.

Additional Information

© 2001 ESO. Article published by EDP Sciences. Received 14 May 2001; Accepted 16 July 2001; Published online 15 October 2001. DT and BTS acknowledge support from NSF and NASA grants. GH and GS acknowledge support from the DLR grant 50 OR 9908 0. LP and GZ acknowledge support provided by ASI through contracts ASI-ARS-99-15 and ASII/R/35/00. Data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

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