Laboratoire d’Astrophysique Ecole Polytechnique Fédérale de Lausanne Switzerland
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Laboratoire d’Astrophysique Laboratoire d’Astrophysique Ecole Polytechnique Fédérale de Ecole Polytechnique Fédérale de
LausanneLausanneSwitzerlandSwitzerland
Strong gravitational lensing as a tool for studying galaxy formation and
cosmologyFrédéric CourbinFrédéric Courbin
For theFor the COSMOGRAIL COSMOGRAIL collaborationcollaborationBologna, January 2008Bologna, January 2008
http://www.cosmograil.net
COSMOGRAIL: the COSmological MOnitoring of GRAvItational LensesCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses
Image
Lens
Source
Observer
DL
DS
DLS
Quasar time delays, HQuasar time delays, H0 0 and galaxy mass profileand galaxy mass profile
Geometry (plus Ho) Radial (mass) profile of the lens
Quasar lensing requiresQuasar lensing requires::
• High-accuracy astrometry (a few milli-arcsec)High-accuracy astrometry (a few milli-arcsec)
• Detailed mapping of the light distribution in the Detailed mapping of the light distribution in the lenslens
• Image of the lensed host galaxy of the quasarImage of the lensed host galaxy of the quasar
• Accurate measurement the time delaysAccurate measurement the time delays
Image deconvolution of HST images is extensively Image deconvolution of HST images is extensively used butused but::
• Lack of PSF stars in the small HST field of viewLack of PSF stars in the small HST field of view
• PSF distortions across the fieldPSF distortions across the field
• Colour dependence of the PSFColour dependence of the PSF
Quasar time delays, HQuasar time delays, H0 0 and galaxy mass profileand galaxy mass profile
HSTHST
GroundGround
Example of a lensed quasar: RX J1131-123Example of a lensed quasar: RX J1131-123
HST / ACSHST / ACS
1.2 m Euler (La Silla)1.2 m Euler (La Silla)
(Sluse et al. 2006, A&A 449, 539, including data from (Sluse et al. 2006, A&A 449, 539, including data from CASTLEs)CASTLEs)
3 arcsec3 arcsec
Euler (Chile) Mercator (La Palma) 2 x 1.2m telescopes
Liverpool 2m Robotic Telescope
Switzerland:Switzerland:
G. MeylanG. MeylanF. CourbinF. CourbinC. VuissozC. VuissozA. EigenbrodA. EigenbrodG. BurkiG. BurkiD. SluseD. SluseP. SahaP. Saha
UK:UK:
S. DyeS. DyeS. WarrenS. Warren
Belgium:Belgium:
P. MagainP. MagainV. ChantryV. ChantryE. EulaersE. EulaersL. Le Guillou L. Le Guillou H. Van H. Van WinckelWinckelC. WaelkensC. Waelkens
UzbekistanUzbekistan::
M. M. IbrahimovIbrahimovI. I. AsfandiyarovAsfandiyarov
Uzbek 1.5m Telescope
IndiaIndia::
T. PrabhuT. PrabhuD. SahuD. SahuC.S. StalinC.S. Stalin
2m Himalayan Chandra Telescope
COSMOGRAIL telescopesCOSMOGRAIL telescopes
WFI 2033-4723WFI 2033-4723
Rather wide angular separation (2-3 arcsec)Rather wide angular separation (2-3 arcsec)
Photometry using MCS deconvolution Photometry using MCS deconvolution (Magain, Courbin, Sohy, 1998, ApJ 494, 472)(Magain, Courbin, Sohy, 1998, ApJ 494, 472)
1.2 m Euler (deconvolved) image1.2 m Euler (deconvolved) imageFWHM = 0.35 arcsecFWHM = 0.35 arcsec
HST ACS image (from CASTLEs)HST ACS image (from CASTLEs)
WFI 2033-4723WFI 2033-4723
Vuissoz et al. Vuissoz et al. 20082008
219 epochs ! 219 epochs !
Sampling Sampling ~ 4 days~ 4 days
3 full years3 full years
WFI 2033-4723WFI 2033-4723
Time delays measured from 3 different methods (Vuissoz et al. Time delays measured from 3 different methods (Vuissoz et al. 2008) :2008) :
B-A = 35.5 ± 1.4 days (3.8%), most of the error is shot noiseB-A = 35.5 ± 1.4 days (3.8%), most of the error is shot noiseB-C = 63.7 ± 3.4 days (5.0%), most of the error comes from B-C = 63.7 ± 3.4 days (5.0%), most of the error comes from systematicssystematics
Slow microlensing is negligible, fast microlensing (scales Slow microlensing is negligible, fast microlensing (scales of weeks) of weeks) is not.is not.
WFI 2033-4723WFI 2033-4723
Shifted Shifted curvescurves
Vuissoz et al. 2008Vuissoz et al. 2008
WFI 2033-4723WFI 2033-4723
Detailed HST-NICMOS (F160W) imaging (from CASTLE):Detailed HST-NICMOS (F160W) imaging (from CASTLE):
• Light profile of the lens (best fit: de Vaucouleurs)Light profile of the lens (best fit: de Vaucouleurs)• Astrometry to 3 mas accuracy including systematicsAstrometry to 3 mas accuracy including systematics• Faint Einstein ringFaint Einstein ring
WFI 2033-4723WFI 2033-4723
Non parametric modelingNon parametric modeling
Twisting of the mass contours Twisting of the mass contours
Dynamical perturbation from group ?Dynamical perturbation from group ?
• Twisted mass iso-contours, suggesting gravitational Twisted mass iso-contours, suggesting gravitational perturbationperturbation
• When the time delays are not fitted, all models agree When the time delays are not fitted, all models agree with the with the data: data: isothermal, de Vaucouleurs, NFWisothermal, de Vaucouleurs, NFW
• When the time delays are used, the best mass model is a When the time delays are used, the best mass model is a central central de Vaucouleur plus NFW dark matter halode Vaucouleur plus NFW dark matter halo
• The twisting of the mass contours and the steep mass The twisting of the mass contours and the steep mass profile of profile of the lens in WFI 2033-4723 suggest the lens is a satellite the lens in WFI 2033-4723 suggest the lens is a satellite rather rather than a central galaxy of a group. than a central galaxy of a group.
WFI 2033-4723WFI 2033-4723
Going beyond HST resolution Going beyond HST resolution
An An iterative PSF constructioniterative PSF construction algorithm is devised: algorithm is devised:
• Start with a TinyTim PSF (Krist & Hook)Start with a TinyTim PSF (Krist & Hook)
• Carry out a first deconvolutionCarry out a first deconvolution
• Remove extended sources in the imageRemove extended sources in the image
• Estimate a new PSF on the point sources in the data Estimate a new PSF on the point sources in the data
• Deconvolve againDeconvolve again
• Do this a few times until the residuals are acceptable Do this a few times until the residuals are acceptable
Magain, Courbin, Gillon, et al. 2007, A&A Magain, Courbin, Gillon, et al. 2007, A&A 461, 373461, 373Chantry & Magain 2007, A&A 470, 467 Chantry & Magain 2007, A&A 470, 467
-> For more details-> For more details
Going beyond HST resolution Going beyond HST resolution
Example of application to NICMOS images of the « cloverleaf »Example of application to NICMOS images of the « cloverleaf »
Original F160W imageOriginal F160W image
1 arcsec1 arcsec
Going beyond HST resolution Going beyond HST resolution
Example of application to NICMOS images of the « cloverleaf »Example of application to NICMOS images of the « cloverleaf »
Modifications applied to the PSF after each deconvolution stepModifications applied to the PSF after each deconvolution step
Chantry & Magain 2007, A&A 470, Chantry & Magain 2007, A&A 470, 467467
Going beyond HST resolution Going beyond HST resolution
Example of application to NICMOS images of the « cloverleaf »Example of application to NICMOS images of the « cloverleaf »
1 arcsec1 arcsec New résolution is 0.05 arcsec New résolution is 0.05 arcsec
Chantry & Magain 2007, A&A 470, Chantry & Magain 2007, A&A 470, 467467
(+ see poster)(+ see poster)
DeconvolvedDeconvolvedHST (F555W+F814W+F160W)HST (F555W+F814W+F160W)
(Eigenbrod et al. 2006, A&A 451, 747; data from CASTLEs)(Eigenbrod et al. 2006, A&A 451, 747; data from CASTLEs)
Going beyond HST resolution:Going beyond HST resolution:the double Einstein ring in SDSS the double Einstein ring in SDSS
0924+020924+02
For the concordance cosmologyFor the concordance cosmology lenses appear to split in two lenses appear to split in two groups:groups:
• isothermal lensesisothermal lenses
• lenses with a lenses with a steeper-than-isothermalsteeper-than-isothermal inner (15 kpc) mass inner (15 kpc) mass profile profile
Most lenses are in groups, often dominated by a brighter Most lenses are in groups, often dominated by a brighter member.member.
Numerical simulations show that galaxies in groups, that Numerical simulations show that galaxies in groups, that have steep mass profiles are satellite galaxies, and that the have steep mass profiles are satellite galaxies, and that the steep profile is transient (e.g. steep profile is transient (e.g. Dobke, King & Fellhauer 2007).
-> The time delay technique allows to infer the details of the -> The time delay technique allows to infer the details of the inner inner structure of galaxies in a range of environmentsstructure of galaxies in a range of environments
-> Estimate Ho independent of standard candles by -> Estimate Ho independent of standard candles by “stacking” lenses“stacking” lenses
-> provided there exist sufficiently high resolution images to -> provided there exist sufficiently high resolution images to interpret the time delaysinterpret the time delays
COSMOGRAIL papers so farCOSMOGRAIL papers so far
I: Simulated light curves I: Simulated light curves Eigenbrod et al. 2005, A&A 436, 25Eigenbrod et al. 2005, A&A 436, 25
II: The double Einstein ring in SDSS J0924+02II: The double Einstein ring in SDSS J0924+02 Eigenbrod et al. 2006, A&A 451, 747Eigenbrod et al. 2006, A&A 451, 747
III: Deep VLT spectroscopy of 7 lensed quasarsIII: Deep VLT spectroscopy of 7 lensed quasars Eigenbrod et al. 2006, A&A 451, 759Eigenbrod et al. 2006, A&A 451, 759
IV: Non parametric modeling of cosmograil IV: Non parametric modeling of cosmograil objectsobjects
Saha et al. 2006, A&A 450, 461Saha et al. 2006, A&A 450, 461
V: First time delay measurementV: First time delay measurement Vuissoz et al. 2007, A&A 464, 845 Vuissoz et al. 2007, A&A 464, 845
IV: Deep VLT spectroscopy of 8 lensed quasarsIV: Deep VLT spectroscopy of 8 lensed quasars Eigenbrod et al. 2007, A&A 465, 51Eigenbrod et al. 2007, A&A 465, 51
VII: First high-accuracy time delay (VII: First high-accuracy time delay (~~3%) 3%) Vuissoz et al. 2008Vuissoz et al. 2008