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Dark Energy: Illuminating the Dark

Dark Energy: Illuminating the Dark. Eric Linder University of California, Berkeley Lawrence Berkeley National Lab. Discovery! Acceleration. Exploring Dark Energy. New quantum physics? Does nothing weigh something? New gravitational physics? Is nowhere somewhere?. Today’s Inflation.

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Dark Energy: Illuminating the Dark

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  1. Dark Energy: Illuminating the Dark Eric Linder University of California, Berkeley Lawrence Berkeley National Lab

  2. Discovery! Acceleration

  3. Exploring Dark Energy New quantum physics?Does nothing weigh something? New gravitational physics? Is nowhere somewhere?

  4. Today’s Inflation super acceleration SNAP constraints Map the expansion history precisely and see the transition from acceleration todeceleration. Test the cosmology framework – alternative gravitation, higher dimensions, etc.

  5. Present Day Inflation Map the expansion history precisely and see the transition from acceleration todeceleration.

  6. Density History of the Universe Map the density history precisely, back to the matter dominated epoch.

  7. Mapping Our History The subtle slowing down and speeding up of the expansion, of distances with time: a(t), maps out cosmic history like tree rings map out the Earth’s climate history. STScI

  8. Cosmic Archaeology Supernovae: direct probe of cosmic expansion Time: 30-100% of present age of universe (When you were 12-40 years old) Cosmic matter structures: less direct probes of expansion Pattern of ripples, clumping in space, growing in time. 3D survey of galaxies and clusters - Lensing. CMB: direct probe of quantum fluctuations Time: 0.003% of the present age of the universe. (When you were 0.003% of your present age, you were 2 cells big!)

  9. The Universe: Early and Late Relic imprints of quantum particle creation in inflation - epoch of acceleration at 10-35 s and energies near the Planck scale (a trillion times higher than in any particle acclerator). These ripples in energy density also occur in matter, as denser and less dense regions. Denser regions get a “head start” and eventually form into galaxies and clusters of galaxies. How quickly they grow depends on the expansion rate of the universe. It’s all connected!

  10. What do we see in the CMB? COBE WMAP Planck POLARBEAR has 2.5x the resolution and 1/5x the noise A view of the universe 99.997% of the way back toward the Big Bang - and much more.

  11. Geometry of Space Escher WMAP/NASA/Tegmark CMB tells us about the geometry of space - flat? curved? But not much about evolution (snapshot) or dark energy (too early).

  12. Type Ia Supernovae • Exploding star, briefly as bright as an entire galaxy • Characterized by no Hydrogen, but with Silicon • Gains mass from companion until undergoes thermonuclear runaway • Standard explosion from nuclear physics Insensitive to initial conditions: “Stellar amnesia” Höflich, Gerardy, Linder, & Marion2003

  13. Standardized Candle Brightness tells us distance away (lookback time t) Brightness Time after explosion Redshift tells us the expansion factor a

  14. Standard Candles Brightness tells us distance away (lookback time) Redshift measured tells us expansion factor (average distance between galaxies)

  15. Discovering Supernovae

  16. Supernova Properties Astrophysics Understanding Supernovae Nearby Supernova Factory Cleanly understood astrophysics leads to cosmology G. Aldering (LBL) High z: “Decelerating and Dustfree” HST Cycle 14, 219 orbits

  17. What makes SN measurement special?Control of systematic uncertainties Each supernova is “sending” us a rich stream of information about itself. Images Nature of Dark Energy Redshift & SN Properties Spectra data analysis physics

  18. Current Data: SNLS Supernova Legacy Survey: Rolling search on CFHT 2003-08; spectra First year results (71 SN), Astier et al. 2006 Expect total of 500-700 SN at z<0.95

  19. Current Data: SNLS Cosmological Constraints: consistent with CDM Astier et al. 2006 Spergel et al. 2006 But current data has no leverage on the dynamics, i.e. w. Analyses assume constant w.

  20. Looking Back 10 Billion Years STScI To see the most distant supernovae, we must observe from space. A Hubble Deep Field has scanned 1/25 millionth of the sky. This is like meeting 12 people and trying to understand the complexity of the entire US!

  21. Looking Back 10 Billion Years STScI

  22. Dark Energy – The Next Generation Dedicated dark energy probe SNAP: Supernova/Acceleration Probe

  23. Design a Space Mission HDF GOODS wide ~104 Hubble Deep Field [SN] plus ~106  HDF [WL] • Redshifts z=0-1.7 • Exploring the last . 10 billion years • 70% of the age of . the universe deep colorful Both optical and near infrared wavelengths to see thru dust.

  24. New Technology Focus star projectors Guider Visible NIR JWST Field of View Spectrograph port Calibration projectors Half billion pixel array 36 optical CCDs 36 near infrared detectors New technology LBNL CCDs

  25. Astrophysical Uncertainties For accurate and precision cosmology, need to identify and control systematic uncertainties.

  26. Beyond Gaussian No extinction (perfect)Extinction correctionW With AV biasWith AV+RV bias Current data quality Linder & Miquel 2004 Gravitational lensing: Few hi z SN  poor PDF sampling Flux vs. magnitude bias Holz & Linder 2004 Extinction bias: One sided prior biases results Dust correction crucial; need NIR

  27. Controlling Systematics Same SN, Different z  Cosmology Same z, Different SN  Systematics Control

  28. Baryon Acoustic Oscillations (CMB) In the beginning...(well, 10-350,000 years after) It was hot. Normal matter was p+,e- – charged – interacting fervently with photons. This tightly coupled them, photon mfp << ct, and so they acted like a fluid. Density perturbations in one would cause perturbations in the other, but gravity was offset by pressure, so they couldn’t grow - merely oscillated. On the largest scales, set by the sound horizon, the perturbations were preserved. M. White The same primordial imprints in thephotonfield show up inmatterdensity fluctuations. Baryon acoustic oscillations = patterned distribution of galaxies on very large scales (~150 Mpc). Galaxy cluster size

  29. Small scale power: velocity distortions Large scale power: mode coupling Bias Baryon Acoustic Oscillations -Standard ruler: we know the sound horizon by measuring the CMB; we measure the “wiggle” scale  distance - Like CMB is simple, linear physics –but require large, deep, galaxy redshift surveys (millions of galaxies, thousand(s) of deg2) - Possibly WFMOS spectral or SNAP photometric survey -Complementary with SNif dark energy dynamic But... Observations givenonlinear, galaxy power spectrum in redshift space Theory predicts linear, matter power spectrum in real space (Plus selection effects of galaxy markers)

  30. Perlmutter SN factory SNLS HST Cluster SN SNAP Baryon Osc.

  31. Growth History of Structure While dark energy itself does not cluster much, it affects the growth of matter structure. Fractional density contrast  = m/m evolves as + 2H= 4Gm  Sourced by gravitational instability of density contrast, suppressed by Hubble drag. Matter domination case: ~ a-3 ~ t-2, H ~ (2/3t). Try ~ tn. Characteristic equation n(n-1)+(4/3)n-(3/2)(4/9)=0. Growing mode n=+2/3, i.e. ~ a .. .

  32. Gravitational Potential • Poisson equation • 2(a)=4Ga2 m= 4Gm(0) g(a) • Growth rate of density fluctuationsg(a)= (m/m)/a • In matter dominated (hence decelerating) universe,m/m ~ a so g=const and =const. • By measuring the breakdown of matter domination we see the influence of dark energy. • Direct count of growth - number of clusters vs. z [tough] • Decay of potentials thru CMB ISW effect [cosmic variance] • Effect of potentials on light rays - gravitational lensing

  33. Gravitational Lensing Gravity bends light… - we can detect dark matter through its gravity, - objects are magnified and distorted, - we can view “CAT scans” of growth of structure

  34. Gravitational Lensing N. Kaiser Lensing by (dark) matter along the line of sight “Galaxy wallpaper”

  35. Gravitational Lensing Lensing measures the mass of clusters of galaxies. By looking at lensing of sources at different distances (times), we measure the growth of mass. Clusters grow by swallowing more and more galaxies, more mass. Acceleration - stretching space - shuts off growth, by keeping galaxies apart. So by measuring the growth history, lensing can detect the level of acceleration, the amount of dark energy.

  36. Cluster Abundances Clusters-- largest bound objects. DE + astrophysics.Uncertainty in mass of 0.1 dex gives wconst~0.1[M. White],w~? Xray: hot gas  gravitational potential  mass Optical: light  mass Clean detections Difficult for z>1 Need optical survey for redshift Detects flux, not mass Only cluster center Assumes simple: ~ne2 Traditional Difficult for z>1 Detects light, not mass Mass of what? Sunyaev-Zel’dovich: hot e- scatter CMB  mass Weak Lensing: gravity distorts images of background galaxies Clean detections Indepedent of redshift Need optical survey for redshift Detects flux, not mass Assumes ~simple: ~neTe Detect mass directly Can go to z>1 Line of sight contamination Efficiency reduced

  37. Cosmic Toolkit The main challenge will be control of systematics -- clean astrophysics to learn new physics The Founder:Supernovae Ia distance-redshiftThe Players on the Field:SN Ia, Weak Lensing Geometric Methods –“lightbulb”: a standard; don’t care how filament works (test it) SN Ia, SN II, Weak Lensing[CCC], Baryon Oscillations Geometry+Mass –“flashlight”: need to know about lens and battery [nonlinear mass distribution]Weak Lensing[structure], Strong Lensing Geometry+Mass+Gas –“torch”: need to know about the wood, flame, wind [hydrodynamics]SZ Effect, Cluster Counts

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