1. How can CMB help constraining dark energy? Licia Verde ICREA & Institute of space Sciences (ICE CSIC-IIEC)

2. Interpretation key: Black background: background material/work by others White background: work I am directly involved with/my biased view

3. The standard cosmological model Spatially flat Universe Power-law, primordial power spectrum Only 6 parameters: WMAP5yr analysis  CDM model  Survived 15 years of data!

4. Dark energy from CMB 2dfGRS H prior WMAPII SN With DE clustering WMAP3

5. Dark energy WMAP5 Komatsu et al (2008)

6. Why so weak dark energy constraints from CMB? WMAP5 Dunkley et al (2008)

7. If I wanted to reconstruct non parametrically V Theoretical physicists: which parameterization? To give you a flavor, assume it is a slowly rolling potential and think about inflation Similar to horizon flow parameters (from Simon et al 2005; Fernandez-Martinez & LV ‘08) H(z) Just integrate to get  (z) You need to have a parameterization (or a model) Can be integrated analytically! No single observation that I know of can give this

8. Why so weak dark energy constraints from CMB? The limitation of the CMB in constraining dark energy is that the CMB is located at z=1090. We need to look at the expansion history (I.e. more than one snapshot of the Universe) WMAP5 Dunkley et al (2008) Several options….

9. THE SYMPTOMS Or OBSERVATIONAL EFFECTS of DARK ENERGY Recession velocity vs brightness of standard candles: dL(z) CMB acoustic peaks: Da to last scattering LSS: perturbations amplitude today, to be compared with CMB Da to z survey Perturbation amplitude at z survey

10. Leading observational techniques to go after dark energy Supernovae Baryonic Acoustic Oscillations (BAO) Weak Lensing Galaxy clusters number counts (expansion history) (growth of structure and expansion history) (mostly growth of structure) Q: A combination of techniques will be best for at least two reasons

11. What if one could see the peaks pattern also at lower redshifts? weak dark energy constraints from CMB? BUT The CMB encloses information about the growth of foreground structures: secondary CMB! Integrated Sachs Wolfe effect Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing. A B C… resort to other probes (and get other things for free)

12. C… resort to other probes Take the “concordance approach” CMB offers an anchor point at a time where Dark energy is unimportant..or is it?

13. Acquaviva & LV 2007 considered a Brans-Dickie model, which looks like L at late times and which has virtually the same Growth of structure as LCDM Example: If you try to “hide” Dark Energy… Still shows up in the concordance approach….

14. What if one could see the peaks pattern also at lower redshifts? weak dark energy constraints from CMB? BUT The CMB encloses information about the growth of foreground structures: secondary CMB! Integrated Sachs Wolfe effect Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing. (cross correlations!) A B C… resort to other probes (and get other things for free)

15. USE the CMB as BACKLIGHT, illuminating the foreground universe High zmid z low z First galaxies Universe is reionized Ostriker-Vishniac Diffuse thermal SZ Cluster formation: Sunyaev-Zel’dovich (SZ) Kinematic SZ Lensing of the CMB The growth of structure is sensitive to dark energy Rich additional science from correlations among effects Extraction of cosmological parameters Initial conditions for structure formation

16. Sunyaev-Zel’dovich (SZ) clusters e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Coma ClusterT electron = 10 8 K Optical: Redshift and Mass mm-Wave: SZ – Compton Scattering X-ray Flux: Mass

17. http://www.physics.princeton.edu/act/ Barcelona, Cardiff, Columbia, Haverford, Inaoe, KwaZulu-Natal, NASA, NIST, UPenn, Princeton, U. Pittsburgh, Rutgers, Toronto, UBC, Cape Town, Universidad Catolica, York College

18. The south pole telescope http://pole.uchicago.edu/public/

19. 19 Kinetic SZ/Ostriker-Vishniac (OV) Non-Gaussian but with CMB frequency spectrum. Spatially distinguishable. Requires a high fidelity map. Amplitude of OV signal determines epoch of reionization. OV power spectrum measures the density and velocity fluctuations at reionization. Bulk velocity of HOT electrons from ionization by the first stars (OV) or in clusters and filaments (KSZ). Bulk Velocity of hot electrons. CMB photon KSZ measures cluster bulk velocity field at low z.

20. Velocities: using the KSZ signal W=-1.0 W=-0.6 (Hernandez-Monteagudo, LV, Jimenez, Spergel 2006) The peculiar velocity field is sensitive to the onset of the late acceleration of the Universe. Recall that KSZ Narrow and deep Wide and shallow

21. Lensing Rees-Sciama Low z (high l ) High z (low l ) Depends on Gravitational potential Lensing and Rees-Sciama (LV, Spergel 2002) ISW, but non-linear

22. Bispectrum : to couple the high z universe (low ) to the low z universe (high ) via the weak lensing signal Balance of 2 competing contributions: =>Decay of gravitational potential (non Einstein de Sitter Universe) =>Amplification due to non-linear gravitational evolution Balance depends on  m and w Consider primordial, lensing & Rees-Sciama:

23. (Verde, Spergel 2002) Bispectrum: Cross correlating primordial-lensing-Rees Sciama Forecast: ACT+WMAP data Fiducial model See also Giovi Baccigalupi, Perrotta 2004 for w(z)

24. What if one could see the peaks pattern also at lower redshifts? weak dark energy constraints from CMB? BUT The CMB encloses information about the growth of foreground structures: secondary CMB Integrated Sachs Wolfe effect Secondary effects: Sunyaev Zeldovich(SZ), Kintetic SZ, Rees-Sciama, Lensing. A B C… resort to other probes (and get other things for free)

25. Investment portfolio

26. Low risk investment Medium risk, medium gain High risk, high potential for return

27. Cosmic clocks: with D. Stern, M. Kamionkowski, R. Jimenez,T. Treu +GDDS - - -WMAP3+SDSS+HST +H(z)

28. GDDS +high z radiogalaxies + Treu et al. 2000 sample From Simon, Verde, Jimenez (2005) After tornado, earthquakes, tsunami warnings and fires…. we got data! Watch this space…

29. Simon et al 05 Assumes Flatness Fernandez-Martinez & LV 08 Relaxing priors including flatness

30. Forecast: need ~1000 high resolution spectra

31. 2 measurements in one? Challenge: scale of interest ~100 Mpc/h: large volumes! Feature: measure BOTH dA and H(z) from 3D clustering Line of sight (radial) Plane of the sky (angular) Pau collaboration. (2008)

32. Spectroscopy or photometry? AAOmega 600K galaxies, z~1 (10% error on w) WFMOS several million galaxies >2012 VISTA, DES, LSST Degrade information in the z direction but is faster & can cover more sky The debate is still open! Could do weak lensing almost for free

33. PAU: Physics of the Accelerating Universe Awarded consolider-ingenio 2010, E. Fernandez, PI Survey ~10000 deg 2 0.1<z<1.0, ~14M LRG galaxies, 100’s M total “Hybrid” technique: narrow band photometry (the best of both worlds?) Likely: dedicated telescope. New camera (~40 narrow band filters) Instituto de fisica de alta energias (IFAE-Barcelona) Instituto de ciencias del Espacio (ICE-Barcelona) Instituto astrofisico de Andalucia (IAA-Granada) Instituto de fisica teorica (IFT-Madrid) Centro de investigaciones[…] (CIEMAT-Madrid) Instituto de fisica corpuscolar (IFIC -Valencia) Puerto de informacion Cientifica(PIC-Barcelona) Close collaboration between particle physicists (theorists and experimentalists) and astrophysicists (theorists and observers) Measures both H(z) and Da(z) http://www.ice.csic.es/research/PAU/PAU-welcome.html goal

34. Bruzual & Charlot 11 Gyr @ z=0.2 THE IDEA: New photometric system

35. Courtesy of A. Fernandez-Soto

36. ALHAMBRA Courtesy of A. Fernandez-Soto

37. Bruzual & Charlot 11 Gyr @ z=0.2 THE IDEA: New photometric system What filters? How?

38. Redshift error degradation Feature width~15Mpc (comoving) Radial direction H(z)Plane of sky direction Da 1M halos, M>3.7d13Msol MICE simulation 27 (Gpc/h)^3 PAU collab. 2008

39. + other science: galaxy formation and evolution, accurate measurement of P(k) and growth through higher-order correlations, primordial non gaussianity, metalicity for halo stars), etc… A mine of information for studying galaxy formation!

40. Example: Clustering of peaks (DM halos) of a non-gaussian density field Dalal et al 08; Matarrese, Verde 2008 f NL =100 General non-gaussianity  x  x  f NL  x    x    IFas motivated by inflation, then

41. Summary: Much ado about nothing Observations indicate that nothing weighs something (but much less than expected) and make the universe accelerate (other options are still Possible, inhomogeneities, gravity, but the result must “look like  ”). Heroic observational effort is on going (we’ll learn not only about dark energy from it) We HAVE TO ask: “how interesting it is really to add yet another significant figure to  or w ?” What would it take to discriminate?discuss My personal view: The answer lies in the interface between Astronomy and Theoretical physics, if we take the “Accelerating universe challenge”, there is no other way. The standard cosmological model is extremely successful, but….

42. Challenges of the accelerating universe: Zero-th order challenge: create a new culture of particle physicists and astronomers working together, theorists and experimentalists First_order challenge: If it is  why is it so small? On this issue astronomers have done their work already (I.e.  is non zero) Now it is the job of theoretical physicists. Second order challenge: is it dynamical? and if so how does it evolve? Third order challenge: “could we have been wrong all along?” did Einstein had the last word on gravity? Or FRW on the metric? The data challenge: Avalanche of data coming soon The systematics challenge: systematic errors in many cases will be the limit

43. “In the middle of difficulty lies opportunity" --- A. Einstein