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COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Authors :
Mansur Ibrahimov
M. Koleva
Malte Tewes
Frederic Courbin
Prasenjit Saha
Dominique Sluse
Pierre Magain
E. Eulaers
Jonathan P. Coles
Virginie Chantry
Yves Revaz
C. Faure
Georges Meylan
H. Van Winckel
I. M. Asfandiyarov
Simon Dye
University of Zurich
Courbin, F
Source :
Astronomy & Astrophysics. 536:A53
Publication Year :
2011
Publisher :
EDP Sciences, 2011.

Abstract

We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B. We measured Delta_t(BC) = 7.8+/-0.8 days, Delta_t(BD) = -6.5+/-0.7 days and Delta_t_CD = -14.3+/-0.8 days. We spacially deconvolved HST NICMOS2 F160W images to derive accurate astrometry of the quasar images and to infer the light profile of the lensing galaxy. We combined these images with a stellar population fitting of a deep VLT spectrum of the lensing galaxy to estimate the baryonic fraction, $f_b$, in the Einstein radius. We measured f_b = 0.65+0.13-0.10 if the lensing galaxy has a Salpeter IMF and f_b = 0.45+0.04-0.07 if it has a Kroupa IMF. The spectrum also allowed us to estimate the velocity dispersion of the lensing galaxy, sigma_ap = 222+/-34 km/s. We used f_b and sigma_ap to constrain an analytical model of the lensing galaxy composed of an Hernquist plus generalized NFW profile. We solve the Jeans equations numerically for the model and explored the parameter space under the additional requirement that the model must predict the correct astrometry for the quasar images. Given the current error bars on f_b and sigma_ap, we did not constrain H0 yet with high accuracy, i.e., we found a broad range of models with chi^2 < 1. However, narrowing this range is possible, provided a better velocity dispersion measurement becomes available. In addition, increasing the depth of the current HST imaging data of HE 0435-1223 will allow us to combine our constraints with lens reconstruction techniques that make use of the full Einstein ring that is visible in this object.<br />12 pages, 10 figures, final version accepted for publication by A&A

Details

ISSN :
14320746, 00046361, and 04351223
Volume :
536
Database :
OpenAIRE
Journal :
Astronomy & Astrophysics
Accession number :
edsair.doi.dedup.....440a9ee61eae37b0ad6fb49a742dd71d
Full Text :
https://doi.org/10.1051/0004-6361/201015709