What Gravitational Lensing tells us Catherine Heymans Institute for Astronomy, University of Edinburgh Six Six things lensing has has told told us us about Dark Matter How How lensing works First First results from from CFHTLenS
1: Dark Matter exists Dark Matter collisionless Galaxies Hot Baryonic Gas (large interaction cross section) Clowe, Bradac Catherine Heymanset al 2006 Darkness Visible 4th Aug 2010
2: Dark Matter is ~Cold, not TeVeS LRGs R Reyes et al 2010 with neutrinos E G (R) = DM Mass(< R) β Clustering of galaxies in annuli R = Ω m f(z)
3: Dark Matter can not be explained by MACHOs microlensing result EROS collaboration: Afonso et al 2003
4: Dark Matter halos have CDM NFW profiles Projected scaled surface mass density A similar analysis can also probe the shape of DM haloes NFW Leauthard et al in prep Modeling needs to include baryonic component
5: Dark Matter can be mapped at high resolution
6: Dark Matter Simon, Heymans et al 2010 can be seen in 3D With photometric redshifts we can reconstruct the matter density in 3D
6: Dark Matter Simon, Heymans et al 2010 can be seen in 3D With photometric redshifts we can reconstruct the matter density in 3D Simon, Heymans et al 2010
lensed background galaxy z = 1.55 Gravitational Lensing lens galaxy z = 0.168
Weak Gravitational Lensing The intervening dark matter lenses the light from distant galaxies.
<e i source > = circle Before lensing galaxies are randomly oriented*
Weak Gravitational Lensing : cosmic shear The lensing effect distorts or shears the images of background galaxies. Dark Matter Galaxies It is the only method that is directly sensitive to mass on large scales irrespective of its state or nature Lensed galaxies align
Dark Matter changes the shapes of galaxies by ~1% Telescopes change the shapes of galaxies by ~10% GREAT10: Kitching et al 2010 We need to understand our instrumentation to a higher precision than ever before
CFHTLenS Area: 171 sq degrees from CFHTLS-Wide Survey Multi-colour depth: ugriz, to i=24.7 (7 sigma extended source) Accurate shear and photometric redshift measurements for ~16 gals per sq arcmin Median redshift: zm = 0.75
The CFHTLenS Team A survey an order of magnitude larger than anything before requires an analysis an order of magnitude better than anything before UBC L. Van Waerbeke (PI) J. Benjamin M. Milkeraitis S.Vafaei Waterloo M Hudson B. Gillis Oxford L. Miller Edinburgh C. Heymans (PI) T. Kitching E. Grocutt Bonn T. Erben K. Holhjem P. Simon Naples L. Fu IAP Y. Mellier C. Bonnett R. Gavazzi Munich M. Kilbinger Tohoku J. Coupon Leiden H.Hildebrandt H. Hoekstra K. Kuijken T. Schrabback E. Semboloni M. Velander E. van Uitert M. Smit JPL/Caltech B. Rowe
CFHTLenS
VVDS Deep 72 sq degrees 49 sq degrees 25 sq degrees 25 sq degrees VIPERS DEEP2 Catherine Heymans VVDS Wide Darkness Visible 4th Aug 2010
New Bayesian Model fitting method + bayesian photometric redshift method 1: Create galaxy model forward FFT, multiply, inverse FFT 3: Convolve galaxy and PSF Compare data and model to maximise likelihood Data + lensing quality data reduction pipeline 2: Select PSF model Reference: Miller et al 2007, Catherine Heymans Kitching et al 2008 Darkness Visible 4th Aug 2010
Gaussianised Photometric Redshifts Gaussianised method i < 24 z phot z phot Standard method i < 24 σz = 0.053 σz = 0.045 outlier = 10.1% outlier = 4.9% z spec z spec Reference: Kuijken 2008, Hildebrandt et al 2009 PSF Catherine Heymans Kernel = Result Darkness Visible 4th Aug 2010
Systematics tests Goal: zero systematics for all field Reality: systematics exist and we require a cosmology-free statistic to reject data with significant systematics Current field rejection rate is 40% Catherine Heymans Darkness Visible 4th Aug 2010
Euclid/LSST ADEPT The Dark Energy Quest DES PS1 VST-KIDS BOSS CFHTLenS Wiggle-Z Catherine Heymans Number of spectra Number of galaxies Big-BOSS BAO Lensing Darkness Visible 4th Aug 2010
Conclusions Lensing is a unique technique that can directly probe dark matter It has provided concrete evidence for the existence of CDM CFHTLenS is the largest deep cosmological survey for lensing: we see DM spanning degree scales Future: VST-KIDS, DES, Euclid, LSST