1. Introduction to Cosmology Ofer Lahav University College London The zoo of cosmological parameters Dark Matter and Dark Energy surveys

2. UCL Astrophysics http://www.star.ucl.ac.uk http://www.star.ucl.ac.uk Approximately 20 academic staff, 15 post-docs, 40 PhDs, 15 support staff Research Areas: Stellar astrophysics, Star formation, Astro-chemistry, Cosmology, Atmospheric Physics, Astro-biology, Instrumentation, Mill Hill Observatory & the MSSL Department UCL founded 1826

3. 18 th Cumberland Lodge meeting July 2005

4. “Nearly Normal Galaxies” conference Santa Cruz 1986

5. cf. Cosmology in 1986  “Standard Cold Dark Matter”  m = 1,   =0 H 0 = 50 km/sec/Mpc = 1/(19.6 Gyr)  Galaxy redshift surveys of thousands of galaxies ( CfA1, SSRS, ORS, IRAS )  Peculiar velocities popular ( 7S )  CMB fluctuations not detected yet

7. F 2MASS Galactic chart

8. Rotation curves of spirals are flat- Dark matter halos (or MOND?)

9. Evidence for Dark Energy  Supernovae as standard candles  CMB – a flat universe  LSS - low  m  Clusters - low  m  Baryon Wiggles as standard rulers  Integrated Sachs Wolfe Geometry vs. Growth of structure Multiple approaches are essential!

10. The Chequered History of the Cosmological Constant  The old CC problem: Theory exceeds observational limits on  by 10 120 ! The new CC problem: Why are the amounts of Dark Matter and Dark Energy so similar?

11. Matter and Dark Energy tell space how to curve:  k =  m +   - 1 Curvature Matter Dark (Vacuum) Energy

12. Matter and Dark Energy tell space how to curve:  k =  m +   - 1 Curvature Matter Dark (Vacuum) Energy  k -   =  m - 1 OR modified curvature

13. The Universe accelerates at present if  m /2 -   < 0 e.g. For  m = 0.3 and   = 0.7  k = 0 (the U. is flat!) and the U. is accelerating! (only ‘recently’, z<0.7)

14. Just Six numbers (?)  Baryons  b  Matter  m  Dark Energy (Cosmological Constant)    Hubble parameter H 0  Amplitude A  Initial shape of perturbations (n = 1 ?)

15.  Through the history of the expansion rate: H 2 (z) = H 2 0 [  M (1+z) 3 +  DE (1+z) 3 (1+w) ] (flat Universe) matter dark energy (constant w) P = w   Comoving distance r(z) =  dz/H(z)  Standard Candles d L (z) = (1+z) r(z)  Standard Rulers d A (z) = (1+z)  1 r(z)  The rate of growth of structure also determined by H(z) and by any modifications of gravity on large scales Probing Dark Matter & Dark Energy

16. Curvature of the Universe bends light

17. CMB Cluster counts Supernovae Baryon Wiggles Cosmic Shear Probes of Dark Matter and Dark Energy Angular diameter distance Growth rate of structure Evolution of dark matter perturbations Standard ruler Angular diameter distance Standard candle Luminosity distance Evolution of dark matter perturbations Angular diameter distance Growth rate of structure Snapshot of Universe at ~400,000 yr Angular diameter distance to z~1000 Growth rate of structure (from ISW)

18. Supernovae Geometric Probe of Dark Energy SDSS

19. The History of CMB observations 1965 1992 2003 Discovery COBE WMAP

20. WMAP3  m = 0.24 +-0.04  8 = 0.74 +-0.06 n = 0.95 +-0.02  = 0.09 +-0.03

21. Observer Dark matter halos Background sources Statistical measure of shear pattern, ~1% distortion Radial distances depend on geometry of Universe Foreground mass distribution depends on growth of structure A. Taylor

22. Recent w from the CTIO Jarvis & Jain, astro-ph/0502243 W=-0.894 +0.156 - 0.208

23. Linder 05 W = P/  W = W 0 + (1-a) W a

24. Sources of uncertainties Cosmological (parameters and priors) Astrophysical (e.g. cluster M-T, biasing) Instrumental (e.g. “seeing”)

25. Bayes’ Theorem  P(A|B) = P(B|A) P(A) / P(B)  P(model | data)= P(data | model) P (model) / P(data) ↑ ↑ ↑ Likelihood Prior Evidence exp (-  2 /2) 1702-1761 (paper only published in 1764)

26. Redshift Surveys

27. Wiener Reconstruction of density and velocity fields from the 2MASS Redshift Survey Erdogdu, Lahav, Huchra et al Astro-ph/0610005

28. The evolution of the Cosmic Web in the past 20 years CfA Great Wall SDSS Great Attractor 2dFGRS

30. From 2dF+CMB (6 parameter fit):  m =0.23 § 0.02 Cole et al. 2005

31. Brief History of ‘Hot Dark Matter’ * 1970s : Top-down scenario with massive neutrinos (HDM) – Zeldovich Pancakes * 1980s: HDM - Problems with structure formation * 1990s: Mixed CDM (80%) + HDM (20% ) * 2000s: Baryons (4%) + CDM (26%) +Lambda (70%): But now we know HDM exists! How much?

32. Neutrinos decoupled when they were still relativistic, hence they wiped out structure on small scales 112 neutrinos per cm 3  WDMCDM+HDMCDM From 2dF  < 0.04 ; M < 1.8 eV (Elgaroy & OL 2003) From Ly-a+SDSS +CMB M < 0.17 eV (Seljak et al. 2006)

33. 2015 CMBWMAP 2/3WMAP 6 yr PlanckPlanck 4yr ClustersAMI SZA APEX AMIBA SPT ACT DES Supernovae Pan-STARRS DESLSST JDEM/ SNAP CFHTLS CSP Spectroscopy ATLAS SKAFMOSKAOS SDSS ImagingCFHTLS ATLASKIDS DES VISTAJDEM/ SNAP LSSTSKA Pan-STARRS SDSS SUBARU Surveys to measure Dark Energy 2005 2015 2005 2010

34. Dark Energy Task Force Recommendations An immediate start of a near- term program (which we call Stage III) designed to advance our knowledge of dark energy and prepare for the ultimate “Stage IV” program, which consists of a combination of large survey telescopes and/or a space mission. Advocate Fisher Matrices!

35. The Dark Energy Survey 4 complementary techniques: * Cluster counts & clustering * Weak lensing * Galaxy angular clustering * SNe Ia distances Build new 3 deg 2 camera on the CTIO Blanco 4m Construction 2005-2009 Survey 2009-2014 (~525 nights) 5000 deg 2 g, r, i, z 300, 000, 000 galaxies with photo-z Cost: $20M

36. The Dark Energy Survey 300,000,000 galaxies over 1/8 of the sky 2009-2014 Multiple Techniques: -Galaxy clustering -Clusters -Supernovae Ia -Weak Gravitational lensing Measure W to a few percent Galactic Dust Map

37. Dark Energy Survey Instrument 3.5 meters Camera Filters Optical Lenses Scroll Shutter 1.5 meters New Prime Focus Cage, Camera, and Corrector for the Blanco 4m Telescope 500 Megapixels, 0.27”/pixel Project cost: ~20M$ (incl. labor)

38. P5 – April 20, 2006 DES Forecasts: Power of Multiple Techniques Frieman, Ma, Weller, Tang, Huterer, etal Assumptions: Clusters:  8 =0.75, z max =1.5, WL mass calibration (no clustering) BAO: l max =300 WL: l max =1000 (no bispectrum) Statistical+photo-z systematic errors only Spatial curvature, galaxy bias marginalized Planck CMB prior w(z) =w 0 +w a (1–a) 68% CL geometric geometric+ growth Clusters if  8 =0.9

39. DUNE: Dark UNiverse Explorer Mission baseline: 1.2m telescope FOV 0.5 deg 2 PSF FWHM 0.23’’ Pixels 0.11’’ GEO (or HEO) orbit Surveys (3-year initial programme): WL survey: 20,000 deg 2 in 1 red broad band, 35 galaxies/amin 2 with median z ~ 1, ground based complement for photo-z’s Near-IR survey (J,H). Deeper than possible from ground. Secures z > 1 photo-z’s SNe survey: 2  £  60 deg 2, observed for 9 months each every 4 days in 6 bands, 10000 SNe out to z ~ 1.5, ground based spectroscopy

40. Baryon Wiggles as Standard Rulers

41. What is the Dark Energy? * Vacuum energy (cosmological constant) * Dynamical scalar field * Manifestation of modified gravity If w= -1.000 then what? New Physics? The Anthropic Principle? Multiverse?