Spectroscopic confirmation of a cluster of galaxies at z=1 in the field of the gravitational lens MG 2016+112
Abstract
We present new optical data on the cluster AX J2019+1127 identified by the X-ray satellite ASCA at z ~ 1 \cite{hattori97}. 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 z ~ 1 galaxy candidates, as already suspected by \cite{benitez99}. Our spectroscopic survey of 44 objects in the field shows an excess of 6 red galaxies securely identified at z ~ 1, with a mean redshift of z =1.005+/- 0.002. We estimate a velocity dispersion of sigma = 771+430-160 km s-1 based on these 6 galaxies and a V-band mass-to-light ratio of 215+308-77 h50 (M/LV)_sun. 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. 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 2001
- DOI:
- 10.1051/0004-6361:20000498
- arXiv:
- arXiv:astro-ph/0006382
- Bibcode:
- 2001A&A...367..741S
- Keywords:
-
- COSMOLOGY: OBSERVATIONS;
- DARK MATTER;
- GALAXIES: CLUSTERS: GENERAL;
- GALAXIES: CLUSTERS: INDIVIDUAL: MG 2016+112;
- GRAVITATIONAL LENSING;
- X-RAYS: GALAXIES;
- Astrophysics
- E-Print:
- 8 pages, 4 figures, uses aa.cls, accepted to Astronomy and Astrophysics with minor changes