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Astron. Astrophys. 324, L1-L4 (1997)


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Letter to the Editor

The geometry of the quadruply imaged quasar PG 1115+080; implications for H0 *

small.htm F. Courbin 1, 2, P. Magain ** 1, C.R. Keeton 3, C.S. Kochanek 3, C. Vanderriest 2, A.O. Jaunsen 4 and J. Hjorth 5

1 Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium
2 URA 173 CNRS-DAEC, Observatoire de Paris, F-92195 Meudon Principal Cédex, France
3 Harvard-Smithsonian Center for Astrophysics, MS-51, 60 Garden Street, Cambridge, MA 02138, USA
4 Institute of Theoretical Astrophysics, University of Oslo, Pb. 1029, Blindern, N-0315 Oslo, Norway
5 NORDITA, Blegdamsvej 17, DK-2100 Copenhagen O, Denmark

Received 15 May 1997 / Accepted 27 May 1997

Abstract

Time delay measurements have recently been reported for the lensed quasar PG 1115+080. These measurements can be used to derive H0, but only if we can constrain the lensing potential. We have applied a recently developed deconvolution technique to analyze sub-arcsecond I band images of PG 1115+080, obtained at the Nordic Optical Telescope (NOT) and the Canada France Hawaii Telescope (CFHT). The high performance of the deconvolution code allows us to derive precise positions and magnitudes for the four lensed images of the quasar, as well as for the lensing galaxy. The new measurement of the galaxy position improves its precision by a factor of 3 and thus strengthens the constraints on the lensing potential. With the new data, a range of models incorporating some of the plausible systematic uncertainties yields [FORMULA] km s-1 Mpc-1.

Key words: gravitational lensing - data analysis

* Based on observations taken at the Nordic Optical Telescope and the Canada France Hawaii Telescope
** Also Maître de Recherches au FNRS (Belgium)

Send offprint requests to: F. Courbin (Liège address)

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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