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J/A+A/488/481       Time delays and H0 from WFI J2033-4723      (Vuissoz+, 2008)

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VII. Time delays and the Hubble constant from WFI J2033-4723. Vuissoz C., Courbin F., Sluse D., Meylan G., Chantry V., Eulaers E., Morgan C., Eyler M.E., Kochanek C.S., Coles J., Saha P., Magain P., Falco E.E. <Astron. Astrophys. 488, 481 (2008)> =2008A&A...488..481V
ADC_Keywords: QSOs ; Gravitational lensing ; Photometry Keywords: gravitational lensing - cosmology: cosmological parameters - quasars: individual: WFI J2033-4723 Abstract: Gravitationally lensed quasars can be used to map the mass distribution in lensing galaxies and to estimate the Hubble constant H0 by measuring the time delays between the quasar images. Here we report the measurement of two independent time delays in the quadruply imaged quasar WFI J2033-4723 (z=1.66). Our data consist of R-band images obtained with the Swiss 1.2m EULER telescope located at La Silla and with the 1.3m SMARTS telescope located at Cerro Tololo. The light curves have 218 independent epochs spanning 3 full years of monitoring between March 2004 and May 2007, with a mean temporal sampling of one observation every 4th day. We measure the time delays using three different techniques, and we obtain Dt(B-A)=35.5±1.4days (3.8%) and Dt(B-C)=62.6+4.1-2.3days (+6.5%-3.7%), where A is a composite of the close, merging image pair. After correcting for the time delays, we find R-band flux ratios of FA/FB=2.88±0.04, FA/FC=3.38±0.06, and FA1/FA2=1.37±0.05 with no evidence for microlensing variability over a time scale of three years. However, these flux ratios do not agree with those measured in the quasar emission lines, suggesting that longer term microlensing is present. Our estimate of H0 agrees with the concordance value: non-parametric modeling of the lensing galaxy predicts H0=67+13-10km/s/Mpc, while the Single Isothermal Sphere model yields H0=63+7-3km/s/Mpc (68% confidence level). More complex lens models using a composite de Vaucouleurs plus NFW galaxy mass profile show twisting of the mass isocontours in the lensing galaxy, as do the non-parametric models. As all models also require a significant external shear, this suggests that the lens is a member of the group of galaxies seen in field of view of WFI J2033-4723. Description: Photometry of WFI J2033-4723, as in Fig. 3 of the paper. The first column gives the Julian date and corresponds to HJD days. The second column is the seeing, in arcsec. Column 3-8 display the photometric measurements of the quasar components A, B and C respectively, with the corresponding error bars. The last column finally provides the name of the telescope used for each measurement. Objects: -------------------------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------------------------- 20 33 42.1 -47 23 43 WFI J2033-4723 = [MCS2004b] WFI J2033-4723 -------------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 58 218 Photometry of WFI J2033-4723, as in Fig.3 of paper
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 10 F10.2 d HJD Julian date 12- 15 F4.2 arcsec Seeing Seeing 17- 21 F5.3 mag magA Magnitude of quasar image A 23- 27 F5.3 mag e_magA Magnitude error bar of quasar image A 29- 33 F5.3 mag magB Magnitude of quasar image B 35- 39 F5.3 mag e_magB Magnitude error bar of quasar image B 41- 45 F5.3 mag magC Magnitude of quasar image C 47- 51 F5.3 mag e_magC Magnitude error bar of quasar image C 53- 58 A6 --- Tel Telescope used (EULER or SMARTS)
Acknowledgements: Christel Vuissoz, christel.vuissoz(at) References: Eigenbrod et al., Paper I 2005A&A...436...25E Eigenbrod et al., Paper II 2006A&A...451..747E Eigenbrod et al., Paper III 2006A&A...451..759E Saha et al., Paper IV 2006A&A...450..461S Vuissoz et al., Paper V 2007A&A...464..845V Eigenbrod et al., Paper VI 2007A&A...465...51E
(End) Christel Vuissoz [EPFL, Switzerland], Patricia Vannier [CDS] 11-Aug-2008
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