Precise weak lensing constraints from deep high-resolution Ks images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2 J 232727.7−020437 at z = 0.70

• Published in: Astronomy and astrophysics (Berlin) Vol. 610
• Main Authors: Schrabback, Tim, Schirmer, Mischa, van der Burg, Remco F. J., Hoekstra, Henk, Buddendiek, Axel, Applegate, Douglas, Bradač, Maruša, Eifler, Tim, Erben, Thomas, Gladders, Michael D., Hernández-Martín, Beatriz, Hildebrandt, Hendrik, Hoag, Austin, Klaes, Dominik, von der Linden, Anja, Marchesini, Danilo, Muzzin, Adam, Sharon, Keren, Stefanon, Mauro
• Format: Journal Article
• Language: English
• Published: Heidelberg EDP Sciences 01.02.2018
• Subjects: Computer simulation; Ellipticity; Galactic clusters; Galaxies; galaxies: clusters: individual: RCS2 J232727.7−020437; gravitational lensing: weak; Image quality; Image reconstruction; Image resolution; Mosaics; Photometry; Point spread functions; Red shift; Sensitivity; Star & galaxy formation; Universe
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201731730

We demonstrate that deep good-seeing VLT/HAWK-I Ks images complemented with g + z-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts 0.7 ≲ z ≲ 1.1, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for Ks imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2 J232727.7−020437 (z = 0.699), combining deep VLT/HAWK-I Ks images (point spread function with a 0.′′35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of 10.1σ. We constrained the cluster mass to $M_{\mathrm{200c}}/(10^{15}~{M}_{\odot}) =2.06^{+0.28}_{-0.26}(\mathrm{stat.})\pm 0.12 (\mathrm{sys.})$ M200c/(1015 M⊙) = 2.06−0.26+0.28(stat.) ± 0.12(sys.) M200c∕(1015M⊙)=2.06-0.26+0.28(stat.)±0.12(sys.) assuming a spherical Navarro, Frenk & White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the z ≳ 0.7 Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal.