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 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:
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RA (2000) DE Designation(s)
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20 33 42.1 -47 23 43 WFI J2033-4723 = [MCS2004b] WFI J2033-4723
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 58 218 Photometry of WFI J2033-4723, as in Fig.3 of paper
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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)
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Acknowledgements: Christel Vuissoz, christel.vuissoz(at)epfl.ch
References:
Eigenbrod et al., Paper I 2005A&A...436...25E 2005A&A...436...25E
Eigenbrod et al., Paper II 2006A&A...451..747E 2006A&A...451..747E
Eigenbrod et al., Paper III 2006A&A...451..759E 2006A&A...451..759E
Saha et al., Paper IV 2006A&A...450..461S 2006A&A...450..461S
Vuissoz et al., Paper V 2007A&A...464..845V 2007A&A...464..845V
Eigenbrod et al., Paper VI 2007A&A...465...51E 2007A&A...465...51E
(End) Christel Vuissoz [EPFL, Switzerland], Patricia Vannier [CDS] 11-Aug-2008