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![Page 1: Complementarity of weak lensing with other probes Lindsay King, Institute of Astronomy, Cambridge University UK.](https://reader036.fdocuments.in/reader036/viewer/2022062718/56649eb15503460f94bb675d/html5/thumbnails/1.jpg)
Complementarity of weak lensing with other probes
Lindsay King,
Institute of Astronomy,
Cambridge University UK
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From Tegmark
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Tereno et al. 2004
future spacecosmic shear
WMAP-1 + CBI
Cosmic shear constraints can be almost orthogonal to CMB
shear survey specs
Provides lever for parameter constraint on small scales
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Lewis 2005
Planck operational~ end 2008
Ignoring CMB lensing biases parameter estimates
Parameter estimation from Planck data
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Gratton, Lewis & Efstathiou ‘07 Lesgourgues et al. ‘06
Neutrino mass: Ly-alpha forest, CMB lensing, Planck constraints
Neutrino masses affect cosmic history & structure formation.A main effect is suppression of power on small scales, roughlyproportional to neutrino contribution to matter content.
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Testing the CDM paradigm on galaxy cluster scales
• Cluster mass function and density profiles are a sensitivetest of cosmology.
• Weak lensing probes scales dominated by dark matter;but relies on having sufficient background galaxies.
• A number of massive high redshift (z~1.4) x-ray clusters have been reported (e.g. Mullis et al. 2005) - possibly indicative of early dark energy (Bartelmann et al. 2006)
• CMB lensing by clusters as a complementary tool?
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Futuristic constraints on clusters from lensing of CMB and weak lensing of galaxies
Lewis & King 2006
space-based, galaxy lensingCMB (polarisation) lensing
500 gal/arcmin sq.photo-z estimates
2 x 0.1 K / 0.5 arcmin pixel on Stokes parameters
Less futuristic constraintsimply CMB lensing betterfor clusters beyond z~0.8
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The inner regions of clusters: home to strongly lensed giant arcs
Li et al. (2006) discuss how giant arc statistics seem to be inconflict with WMAP3; o.depth ~6 below CDM0 (8=0.9 m=0.3).
Even CDM0 must be pushed to be consistent with observations!
• Future surveys will detect thousands of clusters creating giant arcs! Better statistics.
• Campaigns to obtain photometric/spectroscopic redshifts for lensed objects (to which this analysis is sensitive) will increase the power of arcs as a cosmological tool.
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triaxiality
Corless & King ‘07
not isolated
Lokas et al ‘06
ellipticity in potential
Meneghetti et al.
(spectroscopy) (lensing)
King & Corless ‘07
c M
r
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Probing dark matter and baryons on small scales
• Galaxy-galaxy weak lensing probes ensembles of galaxies on scales where dark matter dominates.
• The relationship between baryons and dark matter, as a function of mass and environment, is essential to understanding both galaxy and cluster formation.
• Future surveys will contain ~10^5 strongly lensed galaxies, and ~10^3 strongly lensed quasars!
• Observational requirements covered by weak lensing requirements.
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Strong lensing (+/- stellar kinematics) gives galaxy density profiles very close to isothermal inside E
Koopmans et al 2006
Log density slopes for early-type field lenses(SLACS/LSD)
Average density profile from time delays of 10 lenses
Dobke & King 2006
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On larger scales profiles also consistent with isothermal
• From galaxy-galaxy lensing (e.g. Wilson et al. ‘01, Sheldon et al. ‘04, Mandelbaum et al. ‘06)
• Weak lensing around SLACS strong lenses (Gavazzi et al. 2007)
Gavazzi et al. 2007
• Total density profile closeto isothermal over wide rangeof scales.
• Outer halos of strong lensessimilar to typical field galaxies.
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But for galaxies in denser environments: evidence for deviations from isothermal (e.g. Kochanek et al. ‘06, Dobke et al. ‘07, Read et al. ‘07)
• Simulations show slope changes in strong lensing regions
Dobke, King & Fellhauer 2007
• Tidal truncation of DM halos seen in very dense environments (e.g. Natarayan et al.‘02, Limousin et al.‘07 Halkola et al.‘07)
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On cluster scales probed by weak lensing, halos consistentwith NFW.... Isolated galaxies consistent with isothermal....What about intermediate scales?
We’ve started to carry out a search for large separation lenses in SDSS.
One of the first discoveries is a 10’’ almost compete Einstein ring; lens is a very massive LRG.
Belokurov et al. 2007
Future large surveys will allow us to detect many lenses, and hence study the interplay between baryons and dark matter as a function of mass and environment.
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Testing models of the early universe
• String loops predicted in different amounts by different brane inflation models
Long strings collide & reconnectto form loops
• Of order 10^5 loops compared with ~40 long strings per horizon volume!
Allen & Shellard
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• Strong lenses - Schwarzschild lens well outside loop.
• CLASS/JVAS lens surveys demonstrated advantages of targeting compact, flat spectrum, radio sources.
• Large number of these radio sources in future radio surveys increase detection probability of loop lenses e.g. ~10^8 expected in future half-sky SKA survey.
• Window on the physics of the early universe?
How can we directly detect loops?
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CLASS
LOFAR
SKA (~2020)~10^8 CRSs
Mack, Wesley & King 2007
Looks very promising...
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• The future of weak lensing from space holds great promise.
• Along with other tools, tighter constraints on our cosmologicalmodel will be obtained.
• Massive objects can be probed on a wide range of scales, testing the CDM paradigm and helping us better understand structure formation.
• Future CMB experiments offer a means to study the highest redshift clusters via their lensing signatures.
• Models of brane inflation will be tested by the presence - or absence - of string loop strong lensing events in future radio surveys such as SKA.