Bernard Fort

The Strong Lensing Legacy Survey (SL2S)

ESO Santiago November 22, 2006 UPMC/CNRS

SL2S project

Extract and study a large sample of strong gravitational lenses from the CFHTLS wide field survey

> 300, possibly 1000

with a lens redshift up to z =1:

Institut d’astrophysique de Paris (France)C. Alard, B. Fort, Y. Mellier, Hong Tu (Shangaii NU), J-F Sygnet,

Laboratoire d’Astrophysique de Tarbes-Toulouse (France)R. Cabanac, G. Soucail, E. Belsole (Cambridge UK), R. Pelo

Laboratoire d’astrophysique de Marseille (France)J.-P. Kneib, E. Julo (ESO), L. Tasca, O. le Fevre

UC Santa Barbara (USA)R. Blandford, P. Marshall, R. Gavazzi, ..

University de Victoria (Canada)D. Crampton (HIA) , K.. Thanjavur (UVic), J. Willis (UVic)

Durham University (G-B)M. Swimbank

Scientific collaboration

• CFHT Legacy Survey: a big reservoir of

strong lenses• Automated procedure to search lenses

- arcs in groups and (distant) clusters

- gravitational rings • SL2S scientific goals• Future

Outline of the presentation

CFHTLS/Deep field

170 deg2 (U, G, R, I, Z), I=24.5: 3.8 millions of galaxies

Lensing in cosmology

Newtonian gravitational potentialCosmology Cosmology geometry Newtonian potential

image magnification

For galaxy (QS0) - galaxy lenses (gravitational rings)

- big Elliptical represents 2/3 of the lenses- Optical depth ~ 10-3

Multiple QSOs or arcs around galaxies

- QSO: Cosmic Lens All-Sky Survey 12/5000 distant radiosourcesare lensed by a foreground (E) galaxy (Browne et al 2002) - Galaxy:20 lensed Lyman-α background galaxies for 20,000 massive, E / bulge-dominated galaxies with z>0.4,R<20,B-R>2.2(APM survey: Willis et al, 2000)

Giant arcs in cluster of galaxies

RCS giant arcs sample from Gladders et al 2005.

Some arcs have Einstein radius up to 50 "(A0024, RCS 0224)

Comoving number density of DM halosfrom Mo & White 2002

cluster, Re ~ 7-20"

group Re ~ 3-7"

galaxy, Re ~ 1-3"

Multiple QSOs/Rings

Luminous X-clusters

?

Number of DM halos

predicted n / 1 sq°

Rings -> 10-20

Groups -> 1-2

Clusters -> 0.4

expected CFHTLS

Rings > 1000Groups >100Clusters > 50SHMO > 300 Others ?

SL2S prediction and detection numbers

?

From Oguri 's simulations 2005

How to find rings and arc groups?

observations

SIS mass distribution:

~ 1-3” for a lens galaxy ~ 10-50” for a cluster of galaxies

Can we find intermediate mass lenses ?

(3’’<< 7’’) ?

M ~ 3-30 1012 Mo

(from Mellier 2005).

Visual detection of giant arcs in CFHTLS

Automated detection procedures

Arcfinder (Alard 2006)

Ringfinder (Gavazzi et al 2006

Physical nature of arcs

arc thickness ~ seeing

search a local elongation with w=seeing

2.5 seing~14 pixel

Arcs detector

2.M

2.Mpx

xy

xo,yo

local estimator

I(xo + x, yo) dx

2.M . Max [-M<x<M] [ I(xo + x, yo+y) dy]E(xo,yo) =

Arc reconstruction by a small scale estimator of a local elongation (seeing width) of light distribution

scanning aperture M x M pixel unit (M ~7) unit, optimal mexican hat filtering

(x,y) local axis aligned on second E(xo,yo) moments of light distribution map

with a typical CFHTLS arc candidate

E(x,y) map

Detection example

From Alard 2006

A selected sample of SL2S lenses (10/46T002)

CFHTLS/HST

SL2S/COSMOS 5921+638

Ringfinder fails for rings with Re<2.7 ’’

Preliminary results with CFHTLS

<zl> ~ 0.65

release T002

release T003

groups distant clusters

from Cabanac et al. 2006~ 30°°

Parametric modeling with lenstool

SL2SJ085446-012137

SL2SJ085446-012137

HST modeling of SL2SJ085446-012137

But arc redshift ?

Bright Galaxy {0,0}Main potential x= -0.098’’+/- 0.05y= -0.522’’+/-0.08

Second galaxy produces 2 extra images splitting 7 images configuration

First HST follow-up November 2006

Main fields of investigationsStructure of halos in groups and distant clusters for comparison with simulations:

- center of DM halos relatively to the center of brightest central galaxies, nature of fossile groups

- relative mass and light ratio and evolution with zl

- SL+WL determination of C200= R200/rs for a large mass spectrum from G to clusters as a function of zl

- detection of triaxial halos, study of sub-halos (Rcut), -2D spectroscopy of very distant magnified galaxies and search for galaxies at z>6

«Arcfinder» is not efficient for Re > 2.5-3’’but

we also wantto find the most numerous

population of distant gravitational rings hidden in the CFHTLS ?

« Ringfinder»

Sloan Lens ACS Survey (SLACS) Bolton 2004, Treu 2005, Koopmann 2005

Searching composite spectra for a signature of two aligned galaxies

ACS images

Coupling lensing and stellar dynamics

Lens modelling give the mass at rEinstein andDM

Stars see the potential for r < reff Jeans equation

M* / Lv anisotropy= (M* / L, , v

anisotropyspectro

observation

(~ potential slope

from Koopmann & Treu 2005

SLACS

Lensing -> recovers the Ellipticals fundamental planeFor isolated E (external shear perturbation < 0.035)

<L/*> = 1.01 +/- 0.065 rms

(r) ~ r - 2.01 +/- 0.03 near Einstein Radius (~Flat Rot.Curve)

PA and ellipticity of light and DM trace each other (M*~75%)

No evolution (<10%) of parameters with z (but for SLACS lens galaxies the average redshift is around <ZL>~0.2)

a HDF source

arc(let)s

How to recognize a ring

a HDF Elliptical seeing = 0.8 arcsec

circular source CFHTLS

arc(let)s

circular lens

HST

?

?True G-Ring but spiral like!

Simulations of rings around E-lenses

Finding CFHTLS ring candidates

Detection: Based on color information (often rings are blue and lenses are red (early-type galaxies)Method: Fit a B-R profile consistent with the lens color. Identify a sharp elongated blue excess at 0.8<r<2.5'' above the (B-R) noise.

~10-20 candidates/deg2(Raphael Gavazzi 2006)

SL2S 02 25 11- 04 54 33

A Sample of ringfinder candidates in D1

A spectroscopic follow-up of the arcs is necessary to confirm the candidates

########################################################################## ID RA DEC Re F814w z # #########################################################################

C009 10:00:09.7 02:24:55 2.6 19.3 0.39 C012 10:00:12.6 02:20:15 0.82 18.3 0.39 C013 10:00:13.9 02:22:49 1.7 18.9 0.36 C018 10:00:18.4 02:38:45 1.7 23.2 0.73 C056 10:00:56.7 02:12:26 2.02 18.9 0.42 C148 10:01:48.1 02:23:25 1.48 19.3 0.39 C208 10:02:08.5 02:14:22 1.59 19.88 0.41 C211 10:02:11.2 02:11:39 3.6 21.27 0.91 C216 10:02:16.8 02:29:55 2.1 17.96 0.59 C221 10:02:21.1 02:34:40 1.6 19.2 0.42 C921 09:59:21.7 02:06:38 0.68 18.3 0.44 C929 09:59:29.9 02:13:52 2.4 17.4 0.25

Test with the CFHTLS-COSMOS field

Gavazzi June 2006

4117 (E/So or Sa) galaxies with 18 <I < 22 are selected. 783 with a small residual blue light in the annulus. 72 candidates above the reference threshold. Indeed all the blue cosmos rings are recovered

(but obviously not the red ones). Near future: optimisation + (R-Z, etc.) tests

red ring

red ring

red ring

red ring

A SL2S cosmological tests with rings ?

Hypothesis: Treu's results

<L/*> =1. +/- 0.065

r(r) ~ r - 2.01+/-0.03 at Re ~ Flat Rot. Curve (DM light-conspiracy)

Re/L = Dol Dls /D os

Re/* = G (, or w0,w1)Log r

Re

Lens modeling

VLT spectroscopy

First Year results(~1/5 of the CFHTLS field)

- 47 multiple arc(let) systems in groups and distant clusters were discovered and are being observed

with the HST

- > 100 gravitational ring candidates tbc! - many singly highly magnified lens events with m>3-5)

- Several multi-plan lenses and a few possible dark rings

Several other large (cosmic shear) surveys are planned

Deep lens survey 28 deg2 on goingRCS2 1000 deg2 startedKids-VST/OmegaCAM 1000 deg2VISTA-IR galaxy survey near IR rings ?

LSST 10 000 deg 2 2008Pan-StARRS 10 000 deg 2 2012SNAP Space survey 1000 deg 2 ? >2011

Futur

Extending the technique to near IR survey

• Systematic scan of high magnification regions for Lyman-a emission at z~5-8. Recently z~6 galaxies found this way.

• Small primeval halos: 106 Mo - first stars?

• Dynamical studies with 2D spectroscopy of brightest distant arcs to get rotation curves (Karun Thanjavur, David Crampton, Jon Willis)

SNAPJoint Dark Energy Mission: NASA (75%) & DOE (25%) launch 2014-2015

6 years survey: super novae and weak lensing SNAP: 2m telescope, instrument FOV 1 deg2

Imaging / spectro. one deep field (15 deg2), one large field (~300 deg2 ?) ~ 1Billlion $

• DUNE (Dark Universe Explorer): similar survey but

1.2-1.5m telescope and imaging only instrument FOV 1 deg2

~ 300 M€

•Prediction snap n ~ 4000 and 14000 strong lenses

Conclusions

SL2S will be the largest SL database available for the next 5 years,

possibly 1000 SL, if we have spectroscopic follow-up.

- SL2S will extend the lensing studies of galaxy mass evolution at large z and groups (a new classe of SGL)

- Numerous rings and arc systems for a large mass spectrum allow statistical tests (cf Oguri 2005).

-offer the possibility to observed magnified galaxies at z > 6

- SL2S is a benchmark for the preparation of SL analyses with SNAP or DUNE-like survey.

10 – 30 % of all very distant sources (z>4) are magnified with >10 (Keeton’s prediction 04 astro-ph/0405143)

CFHTLS highly magnified drop-out galaxies

>3

NWFSIE

From Omont et al. 2005

Singly Highly-Magnified Event

Multiple arc system from cosmic string

HST field same HST field + string loop

Finding arcs within clusters members

Typical cases in A1689

Note the cluster shear effect: testing the potential slope

SDSS survey for giant arcs

Sloan 8000 deg2 images to detect clusters using the red sequence technique 0.1<z<0.6 - follow_up with UH88 gives 240 clusters - 141 with sub-arcsecond seeing - 16 with giant arcs and 9 with shortest arcs

Hennawi et al 2006

Inner arc

Arc systems with an elliptical lens.

Radial arc

Cusp arc

Einstein Cross

Fold arc

Singly magnified imageof a distant galaxy

From Kneib et al 1993

Cosmological parameters Dls/Dos

Distribution halos

X-section + conectionLight -> total mass L*-> *->L

Evolution (z)Parametrization ->

An overlook on lensing probability(Ofek, Rix & Maoz 2003)

Optical depth per unit redshift (, zs)

Merging rateLuminosity, M evolution,..

Prob[zlense] variations with various parameters

zsource

m ,

or wo,w1;..

mass evolution

varying

(Ofek, Rix & Maoz 2003) Merger evolution

More information

http://www.cfht.hawaii.edu/~cabanac/SL2S/

The SL2S I:

Cabanac et al. 2006

French/ESA programs

Sloan Lens ACS Survey (SLACS)

Bolton 2004, Treu 2005, Koopmans 2005)Sample ~ 120 candidates with ongoing HST snap

survey

OII 3127ÅZs=1.32

4000 ÅZL=0.63

A three-step procedure to search more rings

2- spectroscopy (VIMOS)Goal find nring ~ 10/°

If successful SL2S => nring ~ 1000 !

1- CFHTLS imageryto select possible SL

ncandidates < 200 /°

3- HST snap>80%

confirmation rate

O L S

Multiple images formation

Convergence+ shear

+ Fermat principle

gravitational lense effects

From SLACS to CFHTLS rings

Finding rings in the CFHTLS-wide is a great challenge (seeing effect), but if successful SL2S => nring ~ 1500 !

Sciences: Evolution lens parameters with z (profile slope, total mass, M/L,..) at larger redshift (0.2-0.8) than the SLOAN survey (<z>~0.2)

Sloan Lens ACS Survey (SLACS) Bolton 2004, Treu 2005, Koopmans 2005 Study ~ 20/120 candidates with ongoing HST snap survey

Schechter distribution L(z)/L*(z)of SIS halos

Faber-Jackson (Tully-Fisher) law

Observational relation (SLOAN) DM = f(*)

dt/dz = n(E, z) (1+z)3 XS c.dt/dz

+

+

<cross-section XSNFW (z)>

Comoving number n NFW (z)(Mo and White 2000)

+

Estimation of the optical depth

Treu et al. 2006Elliptical -> L = *

Analytical method or simulation

Fraction of multiply lensed QSOs ~2.10-3

JVAS + Cosmic Lens All-Sky Survey 12/5000 distant radiosourcesare lensed by a foreground (E) galaxy(astro_ph/0211069, Browne et al; Chae 2002, 2004 , Chen et al, 2004, ApJ 607, L71)

<zlens> ~ 0.4 <Dsource> ~ 4 Gpc

no = 0.5 10-2 Mpc-3, < REinstein> ~ 1 arcsec

for SIS:

~ no < (REinstein)2 > Ds ~ 10-3

Arc modelling with pixel deprojection

HST/ACS : a modelling of a D2/CFHTLS arc by Gavazzi et al. 2005

b/a

b

0.7

5"4"

0.8

Arcs geometry depends on the projection matrix

Projected potential derivatives * Dol . Dls / Dos