Probing the Dark Universe with Weak Gravitational Lensing Andy Taylor Institute for Astronomy, School of Physics, University of Edinburgh, Royal Observatory, Edinburgh, U.K. With David Bacon, Meghan Grey, Michael Brown, Tom Kitching, Chris Wolf, Klaus Meisenheimer, Bhuvnesh Jain 11/15/2018 IDM2004, September, Edinburgh

The “Standard Model” of Cosmology WMAP, SNIa, 2dFGRS, Sloan Digital Sky Survey: 70% Dark Energy 25% Dark Matter 5% Baryonic Matter Spatially flat Four outstanding problems: Dark Matter Dark Energy Inflation Galaxy formation Cosmic Web – bottom up scenario – clusters then filaments then walls (membranes). Note that filaments not well traced by galaxies & too ephemeral to emit x-rays, so lensing only way to detect. (VIRGO Consortium) 11/15/2018 IDM2004, September, Edinburgh

Gravitational Lensing Hubble Space Telescope deep field of a galaxy cluster – the large gravitational lens, Abell 2218. Cosmic Web – bottom up scenario – clusters then filaments then walls (membranes). Note that filaments not well traced by galaxies & too ephemeral to emit x-rays, so lensing only way to detect. 11/15/2018 IDM2004, September, Edinburgh

Gravitational Lensing A simple scattering experiment: Observer Galaxy cluster/lens Background source 11/15/2018 IDM2004, September, Edinburgh

Gravitational Lens Distortions Galaxy ellipticity, e: Lensing effect: e’ = e + 2 g On average <e> = 0. So <e’ >=2g. Shear matrix: Shear matrix Shear matrix Define kappa and gamma Mass sheet degeneracy g = g1 + g2 11/15/2018 IDM2004, September, Edinburgh

IDM2004, September, Edinburgh Weak Lensing An observable is the shear (2-d tidal) matrix: The 2-d lensing scalar potential, f, is a projected Newtonian potential, F: (Take derivatives on sky.) 11/15/2018 IDM2004, September, Edinburgh

Mapping the Dark Matter From shear to projected density (Kaiser & Squires, 1993): Surface potential Surface density = S/Sc (Courtesy A. Refregier) 11/15/2018 IDM2004, September, Edinburgh

Supercluster Abell 901/2 in COMBO-17 Survey z=0.16 R=24.5 A901a A901b A902 1/2 deg 3Mpc/h (Gray & Taylor, et al., 2002, ApJ, 568,141) 11/15/2018 IDM2004, September, Edinburgh

Mass and light in Supercluster A901/2 Dark Matter contours, k. Elliptical galaxy light shading. Error: Dk=0.02 (1-contour) (Gray & Taylor, et al., 2002, ApJ, 568,141) 11/15/2018 IDM2004, September, Edinburgh

Mapping the Dark Matter in 3-D The lens potential, f, is a radial integral over the 3-D Newtonian potential, F: Observer Galaxy clusters/lenses Background source 11/15/2018 IDM2004, September, Edinburgh

Mapping the Dark Matter in 3-D With source distances this can be exactly solved to recover the 3-D Newtonian potential: (Taylor 2001) Observer Galaxy clusters/lenses Background source 11/15/2018 IDM2004, September, Edinburgh

Is 3-D dark matter mapping practical? Shot-noise for 3-D dark matter potential map: So Wiener filter in redshift: Can now resolve clusters. 3-D lensing quality data already exists...COMB0-17 has 17 band photometric redshifts with Dz=0.01. (Bacon & Taylor MN 2003; Taylor, et al MN 2004) (Bacon & Taylor, 2003; Hu & Keeton, 2002) 11/15/2018 IDM2004, September, Edinburgh

The 3-D dark matter potential field Galaxy density: z 1.0 0.8 A901a A901b A902 A901a A901b A902 CB1 0.6 0.4 Cosmic Web – bottom up scenario – clusters then filaments then walls (membranes). Note that filaments not well traced by galaxies & too ephemeral to emit x-rays, so lensing only way to detect. Y X (2-s threshold) 11/15/2018 IDM2004, September, Edinburgh Taylor, et al, 2004 MN, in press

The 3-D dark matter potential and galaxy number density fields Potential Field: Galaxy number density: Cosmic Web – bottom up scenario – clusters then filaments then walls (membranes). Note that filaments not well traced by galaxies & too ephemeral to emit x-rays, so lensing only way to detect. 11/15/2018 IDM2004, September, Edinburgh Taylor, et al, 2004 MN, in press

A901/2 + CB1 Cluster parameters Cluster Redshift M (<0.5Mpc) L(<0.5Mpc) M/L (1013Msun) (1011Lsun) (Msun/Lsun) A901a 0.16 10.8+-2 24.7 43.7 A901b 0.16 8.4+-2 13.6 62.2 A902 0.16 5.1+-3 19.5 26.2 CB1 0.48 12.0+-6 13.0 92.3 Estimate projection-free masses of all objects. Erratic mass-to-light ratio – non-equilibrium system. Modelling with analytic and numerical methods. (Taylor, et al, 2004 MN, in press) 11/15/2018 IDM2004, September, Edinburgh

IDM2004, September, Edinburgh Cosmic Shear Lensing by the large-scale dark matter distribution. First detected by 4 groups in 2000. 11/15/2018 IDM2004, September, Edinburgh

Four random fields in COMBO-17 survey 2-D Dark Matter Maps: Area = 1 sq deg. Depth: z = 0.8. Scale: 10 Mpc/h. Chandra Deep Field South Galactic Pole S11 FDF 11/15/2018 IDM2004, September, Edinburgh

Cosmic Shear Power Spectrum Maximum Likelihood Analysis of Cosmic Shear. Measured over 4 random COMBO-17 fields. R(Mpc/h) 50 5 0.5 zm = 0.85+/-0.05 from photometric redshifts (signal) (noise) Shear Amplitude Standard LCDM model Multipoles Brown, Taylor, et al, 2003, MNRAS, 341, 100 11/15/2018 IDM2004, September, Edinburgh

Results from Cosmic Shear Combine with 2dF Galaxy Redshift Survey & pre-WMAP CMB Wm s8 CMB 2dF GL s8(Wm/0.3)0.49=0.71+/-0.09 Lewis & Bridle (2002) Percival et al (2002) s8 = 0.73+/-0.05 Wm = 0.27+/-0.02 WMAP (h=0.72, t=0.1) Brown, Taylor, et al, 2003, MNRAS, 341, 100 11/15/2018 IDM2004, September, Edinburgh

IDM2004, September, Edinburgh 3-D Cosmic Shear Shear probes the density field at different redshifts: Cosmology Shear-shear cross-power Observer Redshift 11/15/2018 IDM2004, September, Edinburgh

The Growth of Dark Matter Clustering Evolution of the matter power spectrum: 1-sigma Pm(k,z) c2-fit to data. First detection of evolution of Dark matter clustering. A fundamental prediction of Cosmology. 2-sigma LCDM Redshift 11/15/2018 IDM2004, September, Edinburgh (Bacon & Taylor, et al 2004, MN)

Geometric test of Dark Energy (Bhuvnesh Jain & AT, 2003, Phys Rev Lett, 91,1302) Depends only on WV, w = p/r (and Wm+WK). Observer Galaxy cluster/lens z1 zL z2 11/15/2018 IDM2004, September, Edinburgh

Geometric test of Dark Energy Estimate parameters by minimising c2 -fit over all source configurations. Observer Galaxy cluster/lens z1 zL z2 11/15/2018 IDM2004, September, Edinburgh

Geometric test of Dark Energy (with Tom Kitching and David Bacon) Geometric test applied to A901/2 clusters. Dw~0.8 from 3 clusters. Uncertainty scales as: ~1% for darkCAM on VISTA. WV w A901/2 WMAP Cosmic Web – bottom up scenario – clusters then filaments then walls (membranes). Note that filaments not well traced by galaxies & too ephemeral to emit x-rays, so lensing only way to detect. 11/15/2018 IDM2004, September, Edinburgh

Measuring the evolution of Dark Energy Measure Wv and w(a)=w0+wa(1-a). Estimate error for SNAP (zm=1.5). 10% of sky: Dw=~1%, Dwa=~10% wa=0 w0 wa w0 WV 11/15/2018 IDM2004, September, Edinburgh Jain & Taylor, PhysRevLett, 2003

darkCAM on VISTA (area x fov) and timescales: Comparison of lensing telescopes grasp (area x fov) and timescales: VISTA (Visible & Infrared Survey Telescope for Astronomy) darkCAM Proposal to PPARC to start in 2009. (PI: Taylor) w to ~1% accuracy. 3-D dark matter map of sky. 11/15/2018 IDM2004, September, Edinburgh

IDM2004, September, Edinburgh Summary With 3-D lensing (shear + redshifts) we can now measure the 3-D Dark Matter distribution. Detect the growth of Dark Matter clustering. And measure the equation of state of dark energy. Can measure dark energy properties in near future with darkCAM on VISTA. 11/15/2018 IDM2004, September, Edinburgh