Complementarity of weak lensing with other probes
Lindsay King,
Institute of Astronomy,
Cambridge University UK
From Tegmark
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
Lewis 2005
Planck operational~ end 2008
Ignoring CMB lensing biases parameter estimates
Parameter estimation from Planck data
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.
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?
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
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.
triaxiality
Corless & King ‘07
not isolated
Lokas et al ‘06
ellipticity in potential
Meneghetti et al.
(spectroscopy) (lensing)
King & Corless ‘07
c M
r
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.
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
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.
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)
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.
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
• 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?
CLASS
LOFAR
SKA (~2020)~10^8 CRSs
Mack, Wesley & King 2007
Looks very promising...
• 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.
