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