The massive galaxy cluster XMMU J1230.3_s161339 at z ilde 1: colour-magnitude relation, Butcher-Oemler effect, X-ray and weak lensing mass estimates

Abstract

We present results from the multi-wavelength study of XMMU J1230.3_s161339 at z ~ 1. We analyze deep multi-band wide-field images from the Large Binocular Telescope, 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 FUV, NUV and the deep U, B, V, r, i, z data. We achieve an accuracy of $triangle z/(1_s16z)$ = 0.07 (0.04) and the fraction of catastrophic outliers is $eta$ = 13 (0)%, 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 $f_b approx$ 0.5. Further we conduct a weak lensing analysis of the deep 26_s14 $times$ 26_s14 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 fit values are, for the velocity dispersion $sigma_{SIS}$ = 1308 $pm$ 284, concentration parameter c = 4.0$^{_s1614}_{-2}$ and scale radius r$_{s}$ = 345$^{_s1650}_{-57}$ kpc. Combining our mass estimates from the kinematic, X-ray and weak lensing analyses we obtain a total cluster mass of $M^{tot}_{200}$ = (4.56 $pm$ 2.3) $times$ 10$^{14}$ M$_{sun}$. This study demonstrates the feasibility of ground based weak lensing measurements of galaxy clusters up to z ~ 1.