Impact of intrinsic alignments on cosmic shear Shearing by elliptical galaxy halos –SB + Filipe Abdalla astro-ph/ Intrinsic alignments and photozs – SB + Lindsay King arXiv: Cluster counts and cosmic shear – double counting? –Masahiro Takada & SB arXiv: Sarah Bridle, UCL (London)

Cosmic shear (2 point function)

Gravitationally sheared Gravitationally sheared Lensing by dark matter causes galaxies to appear aligned Cosmic shear Face-on view

Intrinsic alignments (II) Croft & Metzler 2000, Heavens et al 2000, Crittenden et al 2001, Catelan et al 2001, Mackey et al, Brown et al 2002, Jing 2002, Hui & Zhang 2002

Tidal stretching causes galaxies to align Adds to cosmic shear signal Intrinsically Aligned (I) Intrinsically Aligned (I) Intrinsic alignments (II) Face-on view

Intrinsic-shear correlation (GI) Hirata & Seljak 2004 See also Heymans et al 2006, Mandelbaum et al 2006, Hirata et al 2007

Galaxies point in opposite directions Partially cancels cosmic shear signal Gravitationally sheared (G) Intrinsically aligned (I) Intrinsic-shear correlation (GI) Face-on view

Cosmic shear two point tomography

Cosmic shear tomography

Cosmic Shear Intrinsic Alignments (IA) Normalised to Super-COSMOS Heymans et al 2004

If consider only w then IA bias on w is ~10% If marginalise 6 cosmological parameters then IA bias on w is ~100% (+/- 1 !) Intrinsic Alignments (IA)

Elliptical galaxy-galaxy lensing Bridle & Abdalla

Background galaxy is gravitationally sheared tangentially around foreground lens Elliptical galaxy-galaxy lensing Face-on view Bridle & Abdalla

Contribution to ellipticity correlation function: Average shear around circular annulus Does not average to zero →net contamination

z 1 =0.3 z 2 =0.8 Average over population visible to R=24 Cosmic shear signal Shear correlation function Bridle & Abdalla

Average over population visible to R=24 Cosmic shear signal Change in cosmic shear signal for  w = 0.05 z 1 =0.3 z 2 =0.8 Shear correlation function Bridle & Abdalla

Removal of intrinsic alignments Intrinsic – intrinsic (II) –Weight down close pairs (King & Schneider 2002, Heymans & Heavens 2003, Takada & White 2004) –Fit parameterized models (King & Schneider 2003) Shear – intrinsic (GI) –Fit parameterized models (King 2005, Bernstein DETF) –Redshift weighting (Schneider talk) Redshift quality is crucial!

Perfect redshifts Scale dependence of IA (# bins) Least flexible model considered FoM is improved! Reasonable model? (14 IA pars) Similar FoM to no IA case Very flexible (100 IA pars) FoM is roughly halved No Intrinsic Alignments Redshift dependence of IA (# bins) 2 3 5

Scale dependence of IA (# bins) Perfect redshifts Redshift dependence of IA (# bins) 2 3 5

Scale dependence of IA (# bins) Realistic photozs σz=0.05(1+z) Redshift dependence of IA (# bins) 2 3 5

Photoz error σz / (1+z) No Intrinsic Alignments FoM / FoM(specz) (e.g. Hu 1999, Ma, Hu, Huterer 2006, Jain et al 2007, Amara & Refregier ) Relatively flat

Photoz error σz / (1+z) Reasonable model? (14 IA pars) Very flexible (100 IA pars) FoM / FoM(specz)

Photoz error σz / (1+z) FoM / FoM(specz) A factor of ~3 better photozs required! (1+z)0.08 (1+z)

Conclusions Lensing by elliptical galaxy halos contributes to shear-intrinsic term (GI) 3x better photozs required to remove intrinsic alignments Cluster counts and lensing power spectra very complementary AD

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Shearing by elliptical galaxy halos Plan: –Calculate shear from elliptical halo –Calculate contribution to shear correlation fn –Average over a population of lenses –Compare with cosmic shear signal –Consider effect of halo profile –Investigate redshift dependence Bridle & Abdalla 2007

Average over population visible to R=24 Cosmic shear signal z 1 =0.3 z 2 =0.8 NFW ^ Shear correlation function

Average over population visible to R=24 NFW ^ Singular isothermal ellipsoid Cosmic shear signal z 1 =0.3 z 2 =0.8 Shear correlation function

M 200 =1x10 12 h -1 M o z lens =0.3 z source =0.8 Shear correlation function Bridle & Abdalla

How good to photozs need to be to remove intrinsic alignments? Plan: –Remove GI, II by marginalising over some flexible model –Look at the effect of GI, II on dark energy errors –Dependence on flexibility of model? –Dependence on photoz errors? Bridle & King 2007

σz / (1+z)

Dark energy from cluster counts and lensing: including the full covariance Plan: –Motivation: combining constraints –Shear power spectrum is from halos –Calculate covariance between cc and cs –Compare with toy model –Calculate signal to noise –Calculate effect on dark energy error bars Takada & Bridle 2007

A toy model Cluster counts Lensing power spectrum

Toy model Full calculation

Toy model Cross correlation coefficient r 10% 100%

Toy model Full calculation Cross correlation coefficient r 10% 1% 100%