Bernard Fort IAP

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The CFHTLS Strong Lensing survey

• Bernard Fort (IAP)
• CoI Olivier Le Fevre Jean-Paul Kneib
  (Marseille)
• Mireille Dantel-Fort (Obs. de Paris)
• Christophe Alard, Yannick Mellier Jean-François
  Sygnet (IAP)
• Raphael Gavazzi Genevieve Soucail (Toulouse)
• Remi Cabanac (CFHT)

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Overview of the presentation

• The CFHTLS imaging / Vimos spectroscopic
  survey
• Which lenses can be seen?
• How many lenses?
• Which scientific objectives can be pursued?
• How to find the lenses?
• A spectroscopic search of source/lens pairs
• Toward an automatic search of lens candidates
  

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The CFHTLS field D1
Petit film de J-C Cuillandre 1 minute Cf fichier
sur la clé
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CFHT Legacy Surveys/ VIMOS

• CFHTLS Deep Fields
• 4 x 1, U, G, R, I, Z, IAB lt 28.4
  
• VLT VIMOS Deep Spectroscopy
• 40 000 spectra, R 5000
• all objects with IABlt 24, ltzspectrogt
  0.76
• . CFHTLS Wide Field
• 170 , IAB lt 24.5

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VVDS 0226-04 cone with 6217 galaxies (Olivier
Lefevre et al 2004)
z1.3
z0.8
z1.2
z1.1
z0.7
z1
z0.6
160Mpc
30Mpc
z0.6
z0.9
z0.5
2DFGRS/SDSS stops here
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CFHTLS scientific drivers in Cosmology

• Formation and evolution of galaxies
• SN survey
• Weak Lensing (Mellier et coll. 2000)
• - recover the shape and amplitude
• of the power spectrum
• - obtain cosmological parameters
• with a better accuracy (Jain,
  Berstein
• Dolney astro-ph 0502243)
• - test gravity on large scales
• (Bernardeau 2005 )

• Strong Lensing (Fort et coll. 2005)
• cosmological tests, by comparing
  observations with simulations (many ref in
  Alcaniz et al 2005, astro-ph/0501026).
• number, ellipticity, profile, mass evolution of
  individual halos (cf CfA-Arizona-ST-Lens-Survey
  Falco et al 1999).
• Singly highly magnified sources (m gt 3)
• Magnification bias expl Keeton 2005
  Almaini et al 2005 astro-ph/0501169 mm sources
  bias)

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A ground for optimism
nh 0.025 halo/Mpc3 Zs gt 2 the line
of sight intersect Nhgt 400 halos.
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Fraction of multiply lensed QSOs 2.10-3
ltzlensgt 0.4, ltDsourcegt 4 Gpc no
0.5 10-2 Mpc-3, lt REinsteingt 1 arcsec for
SIS t no lt p (REinstein)2 gt Ds 10-3
JVAS Cosmic Lens All-Sky Survey
12/5000 distant radiosources are lensed by a
foreground (E) galaxy (astro_ph/0211069, Browne
et al Chae 2002, 2004 , Chen et al, 2004, ApJ
607, L71)

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Various kind of strong lensing "events"

• galaxy (QSO)-galaxy strong lensing events
• multiple arc(let) systems in groups and clusters
• Singly highly magnified lens events (mgt3-5)
• Possible unexpected lens events
• (multi-plan events, dark lenses, cosmic
  strings,..)

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Arcs around galaxies
20 lensed Lyman a background galaxies for 2000
massive, E / bulge-dominated galaxies with
zgt0.4,Rlt20,B-Rgt2.2 (APM survey Willis et al,
2000)
A HSF smple of galaxy- galaxy lenses big
Elliptical represents 2/3 of the lenses
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CFHTLS highly magnified drop-out galaxies
NWF
SIS
Omont et al. 2005
10 30 of all very distant sources are
magnified with mgt10 (Keetons prediction 04
astro-ph/0405143)
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Giant arcs in clusters of galaxies
A CFHTLS gallery of giant arcs from Mellier 2005
discovered in the W3 field.
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Estimate of the optical depth
Schecter distribution L(z)/L(z) of SIS halos
Comoving number n NFW (z) (Mo and White 2000)


Faber-Jackson (Tully-Fisher) law
ltXSNFW (z)gt

Observational relation (SLOAN) sDM f(s)
dt/dz n(qE, z) (1z)3 XS c.dt/dz
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CFHTLS expected number of lens events
(completude IABlt26.5)

• SL type predicted
  number observed (ref.)
• giant arcs 0.1 / sq.
  degree 1 / sq. degree (Mellier
  2005)
• arc(let) systems
• (groups, cluster) 10-20 / sq.
  degree ?
• SGGL (mostly E) 50-70 / sq. degree
  many (HST, GOODS,..)
• Singly H-magnified gt 10-100 / sq. degree (?)
  ?
• others lenses 0 - ? / sq.
  degree

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Giant arcs
10 times more giant arcs in CFHTLS than first
LCDM predictions (Bartelmann et al. 98)
. X-section depends on DM profile and geometry
ellipticity, tri-axiality, source sizes,
external shear, merging (varying caustic
length), central stellar mass,.. (cf. Bartelmann
et al 95, 02, et al., Oguri 02, Guo-Liang Li et
al. 03, Dalal et al. 04, Wambsgans et al. 03,
Menegghetti et al. 04)
Simulations are the only way to calculate
properly t for any peculiar statistical study
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Cosmological tests with arc statistics
DM distribution

• - Frequency of lenses
• Distribution function
• image separation
• redshift lenses
• sources luminosity
• ...

k, g,.. (Dol Dls/Dos) . grad f
O
geometry
.L
a
Dol
Dos
Dls
S
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Probzlense with various parameters

varying q
zsource
W m , Wl
mass evolution
(Ofek, Rix Maoz 2003)
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SNAP or Deep Universe Probe (DUNE) perspective
a Weak Lensing Survey of 300 sq and a deep
SNAP suvey (15 sq) will give respectively 15000
and 4900 lense events (Marshall, Blandford et
al. 2004)
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Simulations of arcs around E-lenses
CFHTLS
HST
circular source
circular lens
?
arc(let)s
arc(let)s
(spiral like!)
?
a HDF source
a HDF Elliptical
seeing 0.8 arcsec
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A spectroscopic search of SG-G L
I
OII 3127Å Zs1.32
4000 Å ZL0.63
G-a I
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First results with VIMOS
11.000 spectra are already available and
candidates are there ( O. Le Fevre, 2005) ! The
CFHTL spectroscopic survey (40 000
spectra) should give more candidates than the
total number of known multiple QSOs!
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Searching arcs around galaxies (GOODS r 0.1
arcsec, 0.3 arcsec lt RE lt 3 arcsec) is
equivalent to search arcs around groups(CFHTLS
r 0.8 arcsec, 3 arcsec lt RE lt 60 arcsecsame
ratio RE / r
An automatic search of arc systems
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CFHTLS schematic software procedure
Eliminate stars select multiplets(n, quad,
triplet,..) with same color (U-G,..)
Sextractor catalogs U,G,R,I,Z
arclets geometry x, y, e, j, dij, .. seeing
Select arclet sytems from generic properties of
lens systems
Mag., S, .. deflector
Test models and flag candidates
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A selection of generic arc(let) systems
radial pair
parallel pair
saddle pair
circular pair
quadruplet
triplet
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Multiple images candidates
It would have been difficult to recognize such
arclet systems when the Einstein radius get
smaller (10 -gt 3 arcsec) Spectroscopic
confirmations are allways needed
F02BiG 1530,13184

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Constraints

• Define a clear selection criteria for each
  lensing event (giant arcs length, magnification,
  limiting surface brightness, zs,..).
• Most parameters depend on observational factors!
• Evaluate observational biases (completude, false
  detections..)

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Working plan (2005-2007)

• define and test best algorithms for the automatic
  
• search procedure on CFHTLS
• Test the robustness of the automatic detection
• number of possible missing events, false
  alarms
• Prepare the statistical lensing analysis

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Immediate scientific targets

• . Detect and model lens systems from groups
• . Study new lens configuration (multi-plan
• lenses,dark lenses, ..)
  
• . Find new arclets sytems in cluster lenses
• . Study the singly highly magnified
  population of
• drop-out galaxies

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Arcs
HST/ACS Cosmos survey Gavazzi, Van
Waerbeke, Mellier, Fort
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Conclusions

• It seems quite possible to develop an automatic
  search of lensing events with five colors per
  field.
• the methodology is tractable but the definition
  of clear selection criteria and the evaluation of
  systematic bias will be a real challenge.