Spectroscopic confirmation of a cluster of galaxies at in the field of the gravitational lens MG 2016+112*
Observatoire Midi-Pyrénées, Laboratoire d'Astrophysique, UMR 5572, 14 avenue E. Belin, 31400 Toulouse, France
2 Institute of Theoretical Astrophysics, University of Oslo, Pb. 1029, Blindern, 0315 Oslo, Norway
3 Centre for Advanced Study, Drammensvn. 78, 0271 Oslo, Norway
4 Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
5 NORDITA, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
6 Astronomical Institute, Tôhoku University, Aoba Aramaki, Sendai 980-77, Japan
Corresponding author: G. Soucail, firstname.lastname@example.org
Accepted: 12 December 2000
We present new optical data on the cluster AX J2019+1127 identified by the X-ray satellite ASCA at [CITE]. The data suggest the presence of a high-redshift cluster of galaxies responsible for the large separation triple quasar MG 2016+112. Our deep photometry reveals an excess of galaxy candidates, as already suspected by [CITE]. Our spectroscopic survey of 44 objects in the field shows an excess of 6 red galaxies securely identified at , with a mean redshift of . We estimate a velocity dispersion of km s-1 based on these 6 galaxies and a V-band mass-to-light ratio of . Our observations thus confirm the existence of a massive structure acting as the lens, which explains the unusual configuration of the triple quasar. Hence, there is no need to invoke the existence of a "dark cluster"to understand this lens system.
Key words: cosmology: observations / dark matter / galaxies: clusters: general / galaxies: clusters: individual: MG 2016+112 / gravitational lensing / X-rays: galaxies
Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Based on observations with the Canada-France-Hawaii Telescope at Mauna Kea, Hawaii, USA.
© ESO, 2001