Christophe Alard (IAP), R

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CFHT- SL2S Strong Lensing Legacy Survey
Rémi Cabanac (CFHT)

• Christophe Alard (IAP), Rémi Cabanac (CFHT),
• Bernard Fort (IAP), Jean-Paul Kneib (LAS),
• Raphael Gavazzi (Santa-Barbara),
• Jean-François Sygnet (IAP),
• Mireille Dantel-Fort (OPM-Terapix),
• G. Soucail, (OMP),
• Yannick Mellier (IAP),
• Phil. Marshall (UC), Sherry Suyu (Caltech),
• Roger Blandford (Stanford),
• Olivier Le Fèvre (LAS), David Valls-Gabaud (OPM)
• ..

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APM survey Willis et al, 2000 20 lensed Lyman-a
background galaxies within 2000 massive, E /
bulge-dominated galaxies with Z gt 0.4, R lt 20,
B-R gt 2.2
RCS1 giant arc sample (Gladders et al 2005) Only
in massive (X-ray) clusters. Giant arcs have
Einstein radius 8" ltRe lt 50 " (e.g. A1689, RCS
0224)
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How to find them?
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The SL2S project

• Develop automated procedure to search the
  lenses
• Make HST imagery and VLT spectroscopy follow-up
• Model and analyse the CFHTLS strong lens sample
• - mass distribution in groups
• - lensing study of distant galaxy up to
  z 1
• Prepare the future (SNAP, DUNE)

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An overview of the CFHTLS-SL2S project
http//www.cfht.Hawaii.edu/cabanac/SL2S/
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Arcs detectors
Arc reconstruction by a small scale estimator of
a local elongation (seeing width) of light
distribution
M
y
x
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

Mpx
xo,yo
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Detection example
A typical CFHTLS arc candidate
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CFHTLS-SL2S Terapix Release T0002
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Modeling of groups halo and sub-halos mass
distribution, halo occupation number, X-ray
connection, evolution M/L,..
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Finding rings in the CFHTLS-wide is a great
challenge (seeing effect), but if successful
SL2S gt 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 (ltzgt0.2)
Sloan Lens ACS Survey (SLACS) Bolton 2004, Treu
2005, Koopmans 2005 Study 20/120 candidates
with ongoing HST snap survey
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Detection Based on color information. 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 0.8ltrlt2.5'' above the (B-?R)
noise.
1-20 candidates/deg2 to be confirmed
spectroscopically (we only expect a few!)
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Result in the CFHTLS-COSMOS field
4117 (E/So or Sa) galaxies with 18 ltI lt 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
Gavazzi June 2006
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SLACS
Lensing -gt recovers the Ellipticals
fundamental plane For isolated E (external shear
perturbation lt 0.035) ltsL/sgt 1.01 /- 0.065
rms r(r) r - 2.01 /- 0.03 near Einstein Radius
(Flat Rot.Curve) PA and ellipticity of light
and DM trace each other ( M75) No evolution
(lt10) of parameters up to z 1 (but more
galaxies around ltZLgt0.2)
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A SL2S cosmological tests with rings ?
Hypothesis Treu's results ltsL/sgt 1.
/- 0.065 r(r) r - 2.01/-0.03 at Re
Flat Rot. Curve (DM
light-conspiracy) Re/sL Dol Dls /D
os Re/s G (W, L, or w0,w1)
Log r
Re
Lens modeling
VLT spectroscopy
Log R
Gavazzi 2006
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• The 300 sq Weak Lensing field
• 15000 lens
• and
• the deep SN survey (15 sq)
• gt 4900 lense events
• (from Marshall, Blandford et al. 2004)

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• SL2S, extrated from CFHTLS, will be the largest
  SL database available for the next 5 years /gt
  1000 SL (still improved automated procedures).
• SL2S will significantly extend the current
  lensing studies in the fields of galaxy
  evolution, uncovering the study of intermediate
  mass halos of groups.
• Gravitational telescope (many magnified high z
  galaxies)
• Numerous rings will allow statistical analysis.
• - SL2S constitutes a benchmark for the
  preparation of SL analyses with SNAP or DUNE-like
  survey.

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Example of data 0047 at z0.485

• 5.75 hrs integration velocity dispersion profile
  to 5

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Method dynamical model

• Two spherical components
• Luminous component Hernquist/Jaffe mass
  distribution
• Dark matter profile generalized NFW profile,
  with inner slope -g , outer slope -3, break
  radius Rb
• Osipkov-Merritt parametrization of the
  anisotropy, or constant anisotropy.

Spherical Jeans equation
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Results. I luminous and dark matter in high-z
E/S0s

• Constant M/L ruled out dark matter halos
  detected!!
• Isotropic or mildly radial orbits
• Approximately flat rotation curve
• Result of (incomplete) violent relaxation?