Complementarity of weak lensing with other probes

Lindsay King, Institute of Astronomy, Cambridge University UK

From Tegmark

Cosmic shear constraints can be almost orthogonal to CMB

future space cosmic shear WMAP-1 + CBI shear survey specs

Tereno et al. 2004

Provides lever for parameter constraint on small scales

Parameter estimation from Planck data Planck operational ~ end 2008

Ignoring CMB lensing biases parameter estimates

Lewis 2005

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, roughly proportional to neutrino contribution to matter content. Gratton, Lewis & Efstathiou ‘07 Lesgourgues et al. ‘06

Testing the CDM paradigm on galaxy cluster scales • Cluster mass function and density profiles are a sensitive test 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 500 gal/arcmin sq.

photo-z estimates space-based, galaxy lensing CMB (polarisation) lensing  2 x 0.1  K / 0.5 arcmin pixel on Stokes parameters Less futuristic constraints imply CMB lensing better for 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 in conflict 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 ellipticity in potential

Corless & King ‘07 (spectroscopy) Lokas et al ‘06 Meneghetti et al.

not isolated

(lensing)

r c M

King & Corless ‘07

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 Log density slopes for early-type field lenses (SLACS/LSD) Koopmans et al 2006 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) • Total density profile close to isothermal over wide range of scales.

• Outer halos of strong lenses similar to typical field galaxies.

Gavazzi et al. 2007

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 consistent with 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 & reconnect to form loops Allen & Shellard • Of order 10^5 loops compared with ~40 long strings per horizon volume!

How can we

directly

detect loops?

• 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?

Looks very promising...

CLASS LOFAR SKA (~2020) ~10^8 CRSs Mack, Wesley & King 2007

• The future of weak lensing from space holds great promise.

• Along with other tools, tighter constraints on our cosmological model 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.