Issue |
A&A
Volume 451, Number 3, June I 2006
|
|
---|---|---|
Page(s) | 759 - 766 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20054454 | |
Published online | 04 May 2006 |
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses
III. Redshift of the lensing galaxy in eight gravitationally lensed quasars
1
Laboratoire d'Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Sauverny, Switzerland
2
Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 août 17, Sart-Tilman, Bat. B5C, 4000 Liège, Belgium
Received:
1
November
2005
Accepted:
21
December
2005
Aims.We measure the redshift of the lensing galaxy in eight gravitationally lensed quasars in view of determining the Hubble parameter H0 from the time delay method.
Methods.Deep VLT/FORS1 spectra of lensed quasars are spatially deconvolved in order to separate the spectrum of the lensing galaxies from the glare of the much brighter quasar images. A new observing strategy is devised. It involves observations in Multi-Object-Spectroscopy (MOS) which allows the simultaneous observation of the target and of several PSF and flux calibration stars. The advantage of this method over traditional long-slit observations is a much more reliable extraction and flux calibration of the spectra.
Results.For the first time we measure the redshift of the lensing galaxy in three multiply-imaged quasars: SDSS J1138+0314 (zlens = 0.445), SDSS J1226-0006 (zlens = 0.517), SDSS J1335+0118 (zlens = 0.440), and we give a tentative estimate of the redshift of the lensing galaxy in Q 1355-2257 (zlens = 0.701). We confirm four previously measured redshifts: HE 0047-1756 (zlens = 0.407), HE 0230-2130 (zlens = 0.523), HE 0435-1223 (zlens = 0.454) and WFI J2033-4723 (zlens = 0.661). In addition, we determine the redshift of the second lensing galaxy in HE 0230-2130 (zlens = 0.526). The spectra of all lens galaxies are typical for early-type galaxies, except for the second lensing galaxy in HE 0230-2130 which displays prominent [OII] emission.
Key words: gravitational lensing / cosmological parameters / quasars: general
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.