Testing the Dark Energy Paradigm Ofer Lahav University College London - Collaborating with Tsvi - Brief History of Dark Energy - The Dark Energy Survey and Euclid - The Next Paradigm Shift?

Less-extreme papers with Tsvi Treyer et al. (1998) XRB LSS Scharf et al. (2000) the XRB dipole (1990) (1997)

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

Dark Energy Pre-SNIa Peebles (1984) advocated Lambda APM result for low matter density (Efstathiou et al 1990) Baryonic fraction in clusters (White et al. 1993) The case for adding Lambda (Ostriker & Steinhardt 1995) Others…

The Dark Energy problem: 10, 90 or 320 years old? The weak field limit of GR: F = -GM/r 2 +  /3 r X * Lucy Calder & OL A&G Feb 08 issue (revised) “I have now explained the TWO principle cases of attraction… which is very remarkable” Isaac Newton, Principia (1687)

“Evidence” for Dark Energy Observational data Type Ia Supernovae Galaxy Clusters Cosmic Microwave Background Large Scale Structure Gravitational Lensing Integrated Sachs-Wolfe Physical effects: Geometry Growth of Structure Both depend on the Hubble expansion rate: H 2 (z) = H 2 0 [  M (1+z) 3 +  DE (1+z) 3 (1+w) ] (flat)

Standard rulers

Baryonic Acoustic Oscillations SDSS Luminous Red Galaxies Density fluctuations CMB WMAP Temperature fluctuations Comving distanceHarmonic l z=0.5 z=1000

The Integrated Sachs-Wolfe Effect gravitational potential traced by galaxy density potential depth changes as cmb photons pass through In EdS the potential is constant with time, hence no ISW effect. An effect is expected in a universe with DE, and it can be detected by cross-correlating the CMB with galaxy maps (Crittenden et al).

Cross-correlation of WMAP and 2MASS Rassat, Land, OL, Abdalla (2006); Francis & Peacock (2009) CCF consistent with no correlation, as well as with   < 0.89 (95% CL)

Probing the Geometry of the Universe with Supernovae Ia ‘Union’ SN Ia sample (Kowalski et al. 2008)

In 3 Dimensions Massey et al. 2007

Spectroscopic Surveys CfA SDSS 2dFGRS

Deviations from standard GR? Bean (2009) using Cosmos2007 Soon with Cosmos2009 Lensing sensitive to the sum of potentials

The Future of the Local Universe  m =0.3 LCDM a = 1 (t= 13.5 Gyr) OCDM a = 1 (t= 11.3 Gyr) LCDM a = 6 (t= 42.4 Gyr) OCDM a = 6 (t= 89.2 Gyr) Hoffman, OL, Yepes & Dover

Galaxy Surveys Photometric surveys: DES, Pan-STARRS, HSC, Skymapper, PAU, LSST, Euclid (EIC), JDEM(SNAP-like), … Spetroscopic surveys: WiggleZ, BOSS, BigBOSS, hetdex, WFMOS/Sumire, Euclid (NIS), JDEM (Adept-like), SKA, …

Photometric redshifts Probe strong spectral features (e.g break) Template vs. Training methods z=3.7z=0.1

MegaZ-LRG Input: 10,000 galaxies with spectra Train a neural network ANNz, Collister & Lahav 2004 Output: 1,000,000 photo-z Collister, Lahav et al Update using 6 photo-z methods *Abdalla et al (Gpc/h) 3 : the largest ever galaxy redshift survey! Photoz scatter of 0.04

1.5M LRGs (“MegaZ”) photo-z code comparison SDSS HpZ+BC Le PHARE Zebra ANNz HpZ+WWC Abdalla, Banerji, OL & Rashkov

Neutrino mass from MegaZ-LRG Thomas, Abdalla & OL (2009) Total mass < 0.3 eV (95% CL)

The Dark Energy

Dark Energy Science Program Four Probes of Dark Energy Galaxy Clusters clusters to z>1 SZ measurements from SPT Sensitive to growth of structure and geometry Weak Lensing Shape measurements of 300 million galaxies Sensitive to growth of structure and geometry Large-scale Structure 300 million galaxies to z = 1 and beyond Sensitive to geometry Supernovae 15 sq deg time-domain survey ~3000 well-sampled SNe Ia to z ~1 Sensitive to geometry Plus QSOs, Strong Lensing, Milky Way, Galaxy Evolution

DES Forecasts: Power of Multiple Techniques FoM factor 4.6 tigther compared to near term projects w(z) =w 0 +w a (1–a) 68% CL

The DES Collaboration an international collaboration of ~100 scientists from ~20 institutions US: Fermilab, UIUC/NCSA, University of Chicago, LBNL, NOAO, University of Michigan, University of Pennsylvania, Argonne National Laboratory, Ohio State University, Santa-Cruz/SLAC Consortium Observatorio Nacional, CBPF,Universidade Federal do Rio de Janeiro, Universidade Federal do Rio Grande do Sul Brazil Consortium: UK Consortium: UCL, Cambridge, Edinburgh, Portsmouth, Sussex, Nottingham Spain Consortium: CIEMAT, IEEC, IFAE CTIO

DES Organization Supernovae B. Nichol J. Marriner Clusters J. Mohr T. McKay Weak Lensing B. Jain S. Bridle Galaxy Clustering E. Gaztanaga W. Percival Photometric Redshifts F. Castander H. Lin Simulations A.Kravtsov A. Evrard Theory W. Hu J. Weller Strong Lensing E. Buckley-Geer M. Makler Galaxy Evolution R. Wechsler D. Thomas QSOs R. McMahon P. Martini Milky Way B. Santiago B. Yanny 11 Science Working Groups Over 100 scientists from the US, UK, Spain and Brazil

The Dark Energy Survey (DES) Proposal: –Perform a 5000 sq. deg. survey of the southern galactic cap –Measure dark energy with 4 complementary techniques New Instrument: –Replace the PF cage with a new 2.2 FOV, 520 Mega pixel optical CCD camera + corrector Time scale: –Instrument Construction Survey: –525 nights during Oct.– Feb –Area overlap with SPT SZ survey and VISTA VHS Use the Blanco 4m Telescope at the Cerro Tololo Inter-American Observatory (CTIO)

The 5 lenses are now being polished C2 Polishing & coating coordinated by UCL (with 1.7M STFC funding) C1

DES Collab. Mtg., OSU, Nov. 8, 2008 Huan Lin 29 A single simulated DECam pointing (= tile = hex) DECam Focal Plane 62 2kx4k Science CCDs (520 Mpix) 1 GB per single 3 deg 2 pointing Image Level Simulations

Neutrino mass from DES:LSS & Planck Lahav, Kiakotou, Abdalla & Blake ( ) Input: M =0.24 eV Output:  M = eV (95% CL)

Total Neutrino Mass DES vs. KATRIN M < 0.1 eV M < 0.6 eV t

Galactic Plane Deep ~40 deg 2 Wide Extragalactic 20,000 deg 2 Euclid Imaging Surveys Wide Survey: Extragalactic sky (20,000 deg 2 = 2  sr) Visible: Galaxy shape measurements to RIZ AB ≤ 24.5 (AB, 10σ) at 0.16” FWHM, yielding resolved galaxies/amin 2, with a median redshift z~ 0.9 NIR photometry: Y, J, H ≤ 24 (AB, 5σ PS), yielding photo-z’s errors of (1+z) with ground based complement (PanStarrs-2, DES. etc) Concurrent with spectroscopic survey Deep Survey: 40 deg 2 at ecliptic poles Monitoring of PSF drift (40 repeats at different orientations over life of mission) Produces +2 magnitude in depth for both visible and NIR imaging data. Possible additional Galactic surveys: Short exposure Galactic plane High cadence microlensing extra-solar planet surveys could be easily added within Euclid mission architecture.

Euclid - impact on Cosmology Euclid Imaging will challenge all sectors of the cosmological model: Dark Energy: w p and w a with an error of 2% and 13% respectively (no prior) Dark Matter: test of CDM paradigm, precision of 0.04eV on sum of neutrino masses (with Planck) Initial Conditions: constrain shape of primordial power spectrum, primordial non-gaussianity Gravity: test GR by reaching a precision of 2% on the growth exponent  (dln  m /dlna  m  )  Uncover new physics and Map LSS at 0<z<2: Low redshift counterpart to CMB surveys Δw p ΔW a ΔΩ m ΔΩ Λ ΔΩ b Δσ 8 Δn s ΔhDE FoM Current+WMAP ~10 Planck Weak Lensing Imaging Probes Euclid Euclid +Planck Factor Gain13>

What will be the next paradigm shift? Vacuum energy (cosmological constant)? Dynamical scalar field? –w=p/  – for cosmological constant: w = -1 Manifestation of modified gravity? Inhomogeneous Universe? What if cosmological constant after all? Multiverse - Landscape? The Anthropic Principle?

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