2011MNRAS.411.2667L

We present results from the multiwavelength study of XMMU J1230.3+1339 at z∼ 1. We analyse deep multiband wide-field images from the Large Binocular Telescope (LBT), multi-object spectroscopy observations from VLT, as well as space-based serendipitous observations, from the GALEX and Chandra X-ray observatories. We apply a Bayesian photometric redshift code to derive the redshifts using the far-UV (FUV), near-UV (NUV) and the deep U, B, V, r, i, z data. We make further use of spectroscopic data from FORS2 to calibrate our photometric redshifts, and investigate the photometric and spectral properties of the early-type galaxies. We achieve an accuracy of {Ux25b5}z/(1 +z)= 0.07 (0.04) and the fraction of catastrophic outliers is η= 13 (0) per cent, when using all (secure) spectroscopic data, respectively. The i-z against z colour-magnitude relation of the photo-z members shows a tight red sequence with a zero-point of 0.935 mag, and slope equal to -0.027. We observe evidence for a truncation at the faint end of the red-cluster-sequence and the Butcher-Oemler effect, finding a fraction of blue galaxies f_b≈ 0.5. Further, we conduct a weak lensing analysis of the deep 26 {x} 26 arcmin r-band LBC image. The observed shear is fitted with a Single-Isothermal-Sphere and a Navarro-Frenk-White model to obtain the velocity dispersion and the model parameters, respectively. Our best-fitting values are, for the velocity dispersion σ_SIS= 1308±284 km/s, concentration parameter c= 4.0⁺¹⁴_–2 and scale radius r_s= 345⁺⁵⁰_–57kpc. From a 38 ks Chandra X-ray observation we obtain an independent estimate of the cluster mass. In addition, we create a signal-to-noise ratio (S/N) map for the detection of the matter mass distribution of the cluster using the mass-aperture technique. We find excellent agreement of the mass concentration identified with weak lensing and the X-ray surface brightness. Combining our mass estimates from the kinematic, X-ray and weak lensing analyses we obtain a total cluster mass of M^tot₂₀₀= (4.56 ±2.3) {x} 10¹⁴ M_☉. This study demonstrates the feasibility of ground-based weak lensing measurements of galaxy clusters up to z∼ 1.

Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota and the University of Virginia. Also based on observations made with ESO Telescopes at the La Silla or Paranal Observatories program ID 081.A-0312. This research has made use of data obtained from the Chandra Data Archive and software provided by the Chandra X-ray Centre (CXC) in the application packages CIAO, CHIPS and SHERPA.