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Letter to the Editor
A ring galaxy at z = 1 lensed by the cluster Abell 370 *
G. Soucail 1,
J.P. Kneib 1,
J. Bézecourt 1,2,
L. Metcalfe 3,
B. Altieri 3 and
J.F. LeBorgne 1
Received 12 January 1999 / Accepted 26 January 1999
We present a study of a very peculiar object found in the field of the cluster-lens Abell 370. This object displays, in HST imaging, a spectacular morphology comparable to nearby ring-galaxies. From spectroscopic observations at the CFHT, we measured a redshift of based on the identification of [OII ] 3727Å and [NeV ] 3426Å emission lines. These emission lines are typical of starburst galaxies hosting a central active nucleus and are in good agreement with the assumption that this object is a ring galaxy. This object is also detected with ISO in the LW2 and LW3 filters, and the mid Infra-Red (MIR) flux ratio favors a Seyfert 1 type. The shape of the ring is gravitationally distorted by the cluster-lens, and in particular by a nearby cluster elliptical galaxy. Using our cluster mass model, we can compute its intrinsic shape. Requiring that the outer ring follows an ellipse we constrain the M/L ratio of the nearby galaxy and derive a magnification factor of 2.5 0.2. The absolute luminosities of the source are then and in the mid-IR.
Key words: galaxies: individual: LRG J0239 0134 galaxies: evolution galaxies: interactions galaxies: Seyfert cosmology: observations cosmology: gravitational lensing
* Based on observations with the NASA/ESA Hubble Space Telescope obtained from the data archive at the Space Telescope European Coordinating Facility, with ISO; an ESA project with instruments funded by ESA Member States with the participation of ISAS and NASA, and with the Canada-France-Hawaii Telescope at Mauna Kea, Hawaii, USA.
Send offprint requests to: G. Soucail (firstname.lastname@example.org)
Online publication: March 1, 1999