Report

Advances and Opportunities in Cosmology at KASI Eric Linder 23 September 2013 Berkeley Center for Cosmological Physics 11 Role of Observations 빨강모자 소녀 But , what big teeth you have! Before we jump into bed with , we should be sure it is not something more beastly. 22 Role of Theory Cosmic acceleration and dark energy are fundamental mysteries in understanding our universe. Copernican Principle / Cosmic Modesty: • Our galaxy is not the center of the universe. • Our particles are not the matter/energy of the universe. • Is our vacuum the vacuum of the universe? • Is our gravity the gravity of the universe? 33 Are We Done? (stat+sys) w(z)? z<1? z>1? There is a long way to go still to say we have measured dark energy! 44 Nature of Dark Energy Dark energy is very much not the search for one number, “w”. Dynamics: Theories other than give time variation w(z). [SN+CMB/BAO] Degrees of freedom: Quintessence has sound speed cs2=1. But generally w(z), cs2(z). Is DE cold (cs2<<1), enhance perturbations? [CMB lensing, WL] Persistence: Is there early DE (at z>>1)? (zCMB)~10-9 but observations allow 10-2. [CMB, CMB x Galaxies] Test Gravity: Expansion vs growth [SN/BAO + CMBlens/WL/Gal] 55 1. Dynamics Models have a diversity of behavior, within thawing and freezing. But we can calibrate w by “stretching” it: w w(a)/ a. Calibrated parameters w0, wa. Caldwell & Linder 2005 de Putter & Linder 2008 The two parameters w0, wa achieve 10-3 level accuracy on This is from physics (Linder 2003). observables d(z), H(z). has nothing to do with a Taylor w(a)=w0+wa(1-a) Itexpansion. 6 6 2. Persistence We have 7 orders of magnitude of unexplored DE(zrec)=10-[2-9] Was there early acceleration (solve coincidence)? Was there early dark energy? Effect of 0.1 e-fold of acceleration Post-recombination, peaks left and adds ISW. Pre-recombination, peaks right and adds SW. Current acceleration unique within last factor 100,000 of cosmic expansion! Linder & Smith 2010 77 Early Expansion Fit real Planck data (+WP) to any deviation from CDM in bins of log a = [-5,-4], [-4,-3.6], [-3.6,-3.2], [3.2,-2.8], [-2.8,0]. Basically testing standard radiation/matter domination in a model independent way. Hojjati, Linder, Samsing 2013 Slight hint of extra radiation energy, i.e. Neff=3.35. 88 3. Perturbations / Microphysics DE internal degrees of freedom can give rise to DE perturbations (inhomogeneity). Only significant when 1+w is not small. Since <w(z<1)> ~ -1, this implies need early dark energy. Perturbations only grow outside the sound horizon ~ cs/H so we need the sound speed cs<<1. Thus persistence early dark energy. Degrees of freedom cold early dark energy. (These go together in many classes of DE theories, e.g. Dirac-Born-Infeld or string dilaton) 99 CMB Lensing CMB as a source pattern for weak lensing. Probes z~1-5 effects, e.g. neutrino masses and early dark energy. Planck gets ~25σ for from CMB lensing. 10 10 CMB Lensing and Cold EDE DE perturbations affect matter power spectrum and so CMB lensing. cs≠1? cvis≠0? Hu 1998 * No EDE EDE * * Calabrese+ 1010.5612 11 11 4. Test Gravity Test gravity in model independent way. Gravity and growth: Gravity and acceleration: Are and the same? (yes, in GR) Tie to observations via modified Poisson equations: Glight tests how light responds to gravity: central to lensing and integrated Sachs-Wolfe. cf Bertschinger & Zukin 2008, Song+ 2011 Gmatter tests how matter responds to gravity: central to growth and velocities ( is closely related). 12 12 Extending Gravity Interesting recent theories extending gravity for cosmic acceleration often have shift symmetries (ϕ ϕ+c) and higher order kinetic terms (ϕμϕμ, related to higher dimensions or massive gravity). From Horndeski general scalar-tensor theory, Charmousis+ 2011 found “Fab 4” unique self tuning terms. De Felice, Linder 2012 promote to nonlinear, mixed function. Appleby, ρ Fab 5 accelerates, has tracker, dS attractor, no extra dof! – and self tuning. It makes invisible! also see Padilla & Sivanesan 2013 H2 13 13 Chasing Down Cosmic Acceleration How can we measure dark energy in detail? A strong program of techniques is in place, but new, complementary probes offer exciting prospects. • Measuring distance to 1% with strong lensing time delays • Measuring growth and gravity to %-level with redshift space distortions 14 14 Strong Lensing Time Delays Strong gravitational lensing creates multiple images (light paths) of a source. When the source is variable (quasar / AGN), we can measure the time delays between the images. This probes the geometric path difference (cosmology) and the lensing potential (dark matter). Key parameter is a distance ratio, the time delay distance 15 15 Time Delays + Supernovae Lensing time delays give superb complementarity with SN distances plus CMB. (Planck) T to 1% for zl=0.1, 0.2,… 0.6 SN to 0.02(1+z)mag for z=0.05, 0.15... 0.95 Factor 4.8 in area Ωm to 0.0044 h to 0.7% w0 to 0.077 wa to 0.26 immunizes vs curvature Linder 2011 16 16 Strong Lensing Distance Surveys Best current distances at 5% accuracy (16 systems known, 2-5 at 5%). 5 year aim: 25 systems, 5% accuracy = 150 orbits HST. Long term: 1% distances. Need 1) high resolution imaging for lens mapping / modeling, 2) high cadence imaging, 3) spectroscopy for redshift, lens velocity dispersion, 4) wide field of view for survey. Synergy: HST/GMT+ LSST/Euclid. Only low redshift z<0.6 needed for lenses. KASI Opportunity – EACOA partner ASIAA has lens modeling expertise - Time domain monitoring (1-2m telescope, CosmoGrail) - AGN flux and time variation expertise - GMT (AO): highest resolution ground telescope - Cosmology expertise on joint probe analysis 17 17 Measuring Time Delays One of the challenges is measuring time delays between images in the presence of 1) noise, 2) gaps, 3) variability, 4) microlensing. We use Gaussian Process statistics to find a family of light curves fitting the data, with correlations. See Holsclaw+ 2010a,b,2011; Kim, Linder, Shafieloo 2012,2013 for cosmology. applications to 18 18 LSST Data Challenge Hojjati, Kim, Linder 2013 Blind fits: Truth: Real data: accurate and more precise than literature. Precision: ~2x improvement (1-2%) Accuracy: within 0.35σ (blind challenge) LSST Data Challenge: “Ladder of Evil” LSST will be a lens finding factory, ~8000 lensed AGN. Strong lensing probes dark energy and dark matter.1919 Higher Dimensional Data Cosmological Revolution: From 2D to 3D – CMB anisotropies to tomographic surveys of density/velocity field. Data, Data, Data – CMB maps l2~10M modes; BOSS maps k3V~0.4M modes; DESI 15M modes 20 Redshift Space Distortions Redshift space distortions (RSD) map velocity field along line of sight. Gets at growth rate f, one less integral than growth factor (like H vs d). Ωm = Linder 2005 gravitational growth index Hume Feldman 21 21 Beyond Linear Kaiser formula inaccurate Even monopole (average over RSD) is poor. Anisotropic redshift distortion hopeless – without better theory. k (h/Mpc) Major approaches are high order perturbation theory, computational simulations – or a new combination of the two. 22 22 High Order Perturbation Theory Putting a rigorous formalism into place: 23 23 High Order Perturbation Theory Applying perturbation theory to simulation and data: Density growth Velocity growth BAO RSD Song, Okumura, Taruya 2013 Distance Hubble parameter 24 24 Simulations + Analytics Simulations allow calibration of RSD into nonlinear regime, where most of the information is. Perturbation theory informs analytic form for linear nonlinear transformation. Ptrue(k,)=F(k) Plin(k,) Kwan, Lewis, Linder 2012 Use simulations to calibrate A, B, C(k,z). k 25 25 Simulations to Fit RSD First results: KLL analytic reconstruction form is accurate to 2-5% out to k=0.5 h/Mpc for z=0-2. (Ppred-Psim)/Psim Vallinotto & Linder 2013 26 26 Dark Energy Spectroscopic Instrument DESI on the Mayall Telescope, Kitt Peak 3D maps of z=0-3.5 20M galaxies, quasars KASI Opportunity – - Spectrocopic survey in optical/NIR - Fiber optic engineering and testing - Cosmology expertise on BAO, RSD (growth/gravity) - High performance computing (KISTI partner?) 27 27 Dark Energy Spectroscopic Instrument 1M LyA QSO 2.5M QSO 18M ELG 4M LRG 100% dark time DOE granted “mission need” 2012 $2.1M Moore grant 2013 CDR milestone Jan 2014 Survey start 2018 KASI Opportunity – - Spectrocopic survey in optical/NIR - Fiber optic engineering and testing - Cosmology expertise on BAO, RSD (growth/gravity) - High performance computing (KISTI partner?) 28 28 Testing Gravity Model independent tests of gravity: two functions, at high/low z, high/low k (8 tests). Simultaneous fit for gravity, expansion (w0, wa), galaxy bias (27 bins). DESI+Planc k Daniel & Linder 2013 Fit all Fix to Fix to b~1/D 29 29 Summary Dark energy is not the search for one number “w”. Explore dynamics, degrees of freedom, persistence. Measuring the growth history, testing growth vs expansion, probes dark energy, gravity, dark matter. Strong program in place + new probes • Strong lensing time delays [HST/GMT; LSST] • Redshift space distortions [DESI] Cosmology at KASI well positioned to use its existing strengths and develop new ones. Science overlap with several groups: GMT, AGN, IR, spectroscopy, fibers. Partnering: ASIAA, KISTI. 30 30