H0LiCOW – X. Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI 2033−4723

Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these perturbation are too large, they can induce a systematic error on H0 of a few per cent if the lens system is used for cosmological inference and the perturbers are not explicitly accounted for in the lens model. In this work, we present a detailed characterization of the environment of the lens system WFI 2033−4723 (⁠zsrc=1.662, zlens=0.6575), one of the core targets of the H0LiCOW project for which we present cosmological inferences in a companion paper. We use the Gemini and ESO-Very Large telescopes to measure the spectroscopic redshifts of the brightest galaxies towards the lens, and use the ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the lens (⁠σlos=250+15−21 km s−1) and of several nearby galaxies. In addition, we measure photometric redshifts and stellar masses of all galaxies down to i < 23 mag, mainly based on Dark Energy Survey imaging (DR1). Our new catalogue, complemented with literature data, more than doubles the number of known galaxy spectroscopic redshifts in the direct vicinity of the lens, expanding to 116 (64) the number of spectroscopic redshifts for galaxies separated by less than 3 arcmin (2 arcmin ) from the lens. Using the flexion-shift as a measure of the amplitude of the gravitational perturbation, we identify two galaxy groups and three galaxies that require specific attention in the lens models. The ESO MUSE data enable us to measure the velocity-dispersions of three of these galaxies. These results are essential for the cosmological inference analysis presented in Rusu et al.Swiss National Science FoundationSwiss National Science Foundation (SNSF); European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programmeEuropean Research Council (ERC) [787886]; World Premier International Research Center Initiative (WPI Initiative), MEXT, JapanMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Packard FoundationThe David & Lucile Packard Foundation; NSFNational Science Foundation (NSF) [AST-1450141, AST-1312329]; Max Planck Society through the Max Planck Research Group; EACOA Fellowship - East Asia Core Observatories Association, Academia Sinica Institute of Astronomy and Astrophysics; National Astronomical Observatory of JapanNational Institutes of Natural Sciences (NINS) - Japan; National Astronomical Observatories of the Chinese Academy of Sciences; Korea Astronomy and Space Science Institute; DFG cluster of excellence 'Origin and Structure of the Universe'German Research Foundation (DFG); NASA through STSCI grant [HSTGO-15320]; U.S. Department of EnergyUnited States Department of Energy (DOE) [DE-AC02-76SF00515]; NWO-VICI career grant [639.043.308]; European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) [091.A-0642(A), 074.A-0302(A), 60.A-9306(A), 097.A-0454(A), 090.A-0531(A)]; U.S. Department of EnergyUnited States Department of Energy (DOE); U.S. National Science FoundationNational Science Foundation (NSF); Ministry of Science and Education of SpainMinistry of Education and Science, Spain; Science and Technology Facilities Council of the United KingdomScience & Technology Facilities Council (STFC); Higher Education Funding Council for EnglandHigher Education Funding Council for England; National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign; Kavli Institute of Cosmological Physics at the University of Chicago; Center for Cosmology and Astro-Particle Physics at the Ohio State UniversityOhio State University; Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University; Financiadora de Estudos e ProjetosCiencia Tecnologia e Inovacao (FINEP); Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro; Conselho Nacional de Desenvolvimento Cientifico e TecnologicoNational Council for Scientific and Technological Development (CNPq); Ministerio da Ciencia, Tecnologia e Inovacao; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG); Argonne National LaboratoryUnited States Department of Energy (DOE)University of Chicago; University of California at Santa Cruz; University of CambridgeUniversity of Cambridge; Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid; University of ChicagoUniversity of Chicago; University College London; DES-Brazil Consortium; University of Edinburgh; Eidgenossische Technische Hochschule (ETH) ZurichETH Zurich; Fermi National Accelerator LaboratoryUnited States Department of Energy (DOE)University of Chicago; University of Illinois at Urbana-Champaign; Institut de Ciencies de l'Espai (IEEC/CSIC); Institut de Fisica d'Altes Energies; Lawrence Berkeley National LaboratoryUnited States Department of Energy (DOE); Ludwig-Maximilians Universitat Munchen; associated Excellence Cluster Universe; University of MichiganUniversity of Michigan System; National Optical Astronomy ObservatoryNational Science Foundation (NSF)NSF - Directorate for Mathematical & Physical Sciences (MPS); University of Nottingham; Ohio State UniversityOhio State University; University of Pennsylvania; University of Portsmouth; SLAC National Accelerator Laboratory; Stanford UniversityStanford University; University of Sussex; Texas AM University; OzDES Membership Consortium; National Science FoundationNational Science Foundation (NSF) [AST-1138766, AST-1536171]; MINECO [AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV-20160597, MDM-2015-0509]; ERDF funds from the European Union; CERCA program of the Generalitat de Catalunya; European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013); ERCEuropean Research Council (ERC) [240672, 291329, 306478]; Brazilian Instituto Nacional de Ciencia e Tecnologia (INCT) e-Universe (CNPq)National Council for Scientific and Technological Development (CNPq) [465376/2014-2]; U.S. Department of Energy, Office of Science, Office of High Energy PhysicsUnited States Department of Energy (DOE) [DE-AC02-07CH11359]; NASANational Aeronautics & Space Administration (NASA) [NAS 5-26555]; NASA through Space Telescope Science InstituteSpace Telescope Science Institute [12889]; National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA); National Science FoundationNational Science Foundation (NSF)This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu