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Comments and Questions about the Dark Universe

Comments and Questions about the Dark Universe. Charling TAO CPPM & Université de la Méditerranée Tsinghua 2005 tao@cppm.in2p3.fr. Outline of the presentation. 1) Brief introduction on SuperNovae 2) Present SNIa data

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Comments and Questions about the Dark Universe

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  1. Comments and Questions about theDark Universe Charling TAO CPPM & Université de la Méditerranée Tsinghua 2005 tao@cppm.in2p3.fr

  2. Outline of the presentation 1) Brief introduction on SuperNovae 2) Present SNIa data 3) Determination of cosmological parameters: a concordant or a convergent Universe? 4) « Experimentalist » point of view: SNIa: « 2 s »  effect? Perhaps too early to speak about new physics !?! 5) How can SN results be improved? 6) Need for more theoretical work 7) What about Cosmology tests in the lab?

  3. Supernovae • Exploding stars  Brightest objects in Universe • Can sometimes be seen by eyerare! 8 recorded in 2000 years • Historical (super) novae • Chinese records 185, 369, 1006 (arabo-persian also), 1054, 1181. • 1572 (Tycho Brahe), 1604 (Kepler) • visible during the day • 1987A LMC : UV, X, radio, visible, + neutrinos !

  4. Historical SN Classification SN Spectra • Type I : absence of hydrogen +Type Ia: presence of ionised Silicium (SiII) +Type Ib: absence of silicium, presence of helium +Type Ic: absence of silicium and helium • Type II: Presence of hydrogen Ha and Hb + Type II normal: domination of hydrogen, presence of helium. IIL (linear) or IIP (plateau) according to Light curves +Type IIb : Dominating presence of helium • Peculiar types

  5. Supernovae: explosions Red giant White dwarf Chandrasekhar mass 1.4 MO Core Collapse SN SNIa : 2 stars (a white dwarf +…)

  6. Interest of SN study • Physics of galaxies: ISM heavy elements and star formation • Physics of stars: explosion at end of star life • Particle Physics: neutrinos properties • Philosophy: We are supernovae dust • Cosmology: distance indicators(SNIa)

  7. Equations of evolution of the Universe General Relativity Matter and energy impact the geometry of the Universe and its evolution. => Equation of movement Friedmann equation . . M=matter R=radiation X=exotic L= cosmological constant k=curvature • Equation of state:w=p/ (w=-1 for )describes the change in the Hubble parameter and impacts: • angular distance - diameter • structures growth rates • Large Scale Structures (LSS) power spectra • Weak Lensing (WL) power spectra • …. (Ma, Caldwell, Bode & Wang , 1999)

  8. Measuring distances Cosmology: additional a(t) scale factor D(t) = a(t) D(t0) a(t) = a0(1+ H0t -1/2 q0 (H0t)2 + …) SN 1996 H0 = Hubble parameter measures the expansion rate of the Universe H0= (a/a)0 = 100 h km/s/Mpc , h= 0.72 +/- 0.05 (?) q0 = deceleration parameter A Universe with only matter is expected to decelerate . .

  9. The Hubble diagram with SNIa Less luminous/z => Accelerated expansion less matter or more dark energy Too luminous/z => Slowed down expansion => deceleration More matter, less dark energy Absolute magnitude m(z) = M + 5 log (DL(z,WM,WL))-5log(H0)+25

  10. The “classical” SN observation method A 3 steps method: • Discovery: subtraction from a reference image. • Supernova type identification and redshift measurement • Photometric follow-up: light curve spectrum Final analysis: Hubble diagram.

  11. SN Ia are not exact standard candles! The light of SNIa explosions can be followed up for several weeks with telescopes

  12. Different standardisation methods Standardisation to Dm =0.2 Before:mB After, eg, stretch correction: mBcor = mB – a (s-1) Different standardisation methods :stretch (SCP), MLC2k2 (HiZ), Dm15, ...

  13. The « classical » method data analysis physics galaxy magnitude z(redshift) Images Hubble + identification. Spectra Ia

  14. Fit cosmological parameters • From Hubble diagram, fit models • Determine dark energy parametersWL, or (WX, w, w’)and matter densityWM mag z 1

  15. SNIa SURPRISE: Indication for negative deceleration parameter q0 Acceleration!!! W = r(t)/rc(t) = WM+ WL • = 1- Wk L = L/3H02 q0= 1/2 WM- WL < 0 z

  16. 2) SN Ia : the present status a selection by Riess et al,astro-ph 0402512 16 new SN Ia with HST(GOOD ACS Treasury program) 6 / 7 existing with z >1.25 + Compilation (Tonry et al. 2003): 172 with changes from… * Knop et al, 2003, SCP : 11 new 0.4 < z < 0.85 reanalysis of 1999, Perlmutter et al. *15 / original 42 excluded/inaccurate colour measurements and uncertain classification * 6 /42 and 5/11: fail « strict  SNIA » sample cut * Barris et al, 2003, HZT: 22 new:varying degrees of completeness on photometry and spectroscopy records * Blakesly et al, 2003 : 2 with ACS on HST • + Low z : 0.01 < z < 0.15 • Calan-Tololo (Hamuy et al., 1996) : 29 • CfA I (Riess et al. 1999): 22 • CfA II (Jha et al, 2004b): 44

  17. SN Ia 2004 : Riess et al, astro-ph 0402512 183 SNIa selected  Gold set of 157 SN Ia WM=0.29 WL=0.71 Prior: Flat Universe But also non concordant models Fits well the concordance model : c2= 178 /157 SNe Ia

  18. Riess et al. (fit quality)

  19. Determination of Cosmological parameters w=p/r w= w0+w’ z Riess et al, astro-ph 0402512

  20. Some Phenomenological work on SNIa Virey, Ealet, Tao, Tilquin, Bonissent, Fouchez, Taxil astro-ph/0407452 Simulation and analysis tool: Kosmoshow developed in IDL by André Tilquin (CPPM) marwww.in2p3.fr/~renoir/Kosmoshow.html

  21. Example of possible bias: large w1 4-fit Ms, WM, w0 , w1 3-fit, Ms, WM, w0 • Suggestion Maor et al... • w0F=-0.7 • w1F= 0.8 • WM= 0.3 Beware of fitting method !!! Bias from the time evolution of the equation of state astro-ph/0403285, Virey et al. Quantitative analysis of the bias on the cosmological parameters from the fitting procedure,ie, assuming a constant w, when it is not! With present statistics, can be ignored Not the case with larger samples!

  22. Riess 2004, gold sample Riess Fit with no prior LCDM concordant model

  23. Riess et al. SNIa data: results for different fits (157 SN Ia « gold sample »  Riess et al., astro-ph/040251) w = p/r = w0+ w1z Results Riess et al… • SN data seem to prefer larger Wm • Instability of results with fits • Errors on w1 are ”small” only if Wm ~ 0.3

  24. 3) Reanalysis of Riess et al. SNIa data A concordant or a converging Universe ? Virey et al., astro-ph 0407452 • With prior WM = 0.27 +/- 0.04, always LCDM (ie w=-1) reconstructed, even with different assumptions in simulations , eg, WM = 0.48 , w=/=-1 •  LCDM convergent model !?! • Without flat prior, NO strong constraints from SNIa • Prior: Flat Universe , but no prior on WM • SNIa  WM = 0.48 preferred value Is WM = 0.27 +/- 0.04 ???

  25. Many determinations of WM Riess et al., astro-ph/0402512 SN WM = 0.27 +/- 0.04 X Freedman and Turner, Rev.Mod.Phys. (astro-ph/0308418) WM = 0.29 +/- 0.04 • WMAP: CMB Bennett et al., 2003 ApJS, 148, 1 with h=0.71 +/- 0.05  0.27 +/- 0.04 Spergel et al. 2003 ApJS, 148, 175 • CMB alone WM h2 = 0.14 +/- 0.02  0.27 +/- 0.10 • CMB + 2dFGRS WMh2 = 0.134 +/- 0.006 with h=0.72 +/- 0.05 0.26 +/- 0.04 • 2dFGRS Hawkins et al., astro-ph/0212375 MNRAS, only bias Tegmark et al. astro-ph/03107253D power spectrum of galaxies from SDSS • astro-ph/0310723Cosmological parameters from SDSS and WMAP, • Clusters, Weak Lensing, etc…. N. Bahcall et al. Comparison M/L data/simulationWM = 0.16 +/-0.05 S. Vauclair et al. XMM X-ray clustersWM > 0.85

  26. What is Cosmic Microwave Background? • Penzias et Wilson(1965)Giant Bell LabRadio Antenna for detection of intergalactic radio emission • Noise excess in all directions (7,5 cm l) Black body radiation at 3.7 +/- 1 o K Planck’s Law • Cosmological Interpretation: Dicke, Wilkinson + Peebles, Roll • Big Bang  Relic radiation • (Gamow (1948) et Alpher et Herman (1950)) Black Body radiation curve COBE (1992) from 0.5 to 5mm T= 2.728 +/- 0.002 K (T= 2.72528 +/- 0.00065 K)

  27. Anisotropies Homogène non isotrope Isotrope non homogène Simulation de galaxies Ned Wright Cosmology tutorial • Anisotropies can be generated by many effects: • acoustic, Doppler, gravitational redshift, photons scattering, … • Complex phenomena ? • Initial surprise : Weakness of the observed effect

  28. A very isotropic CMB

  29. First measured anisotropies • dipole radiation from the Milky Way (1969) Milky Way horizontal in the centre +v/c T0 -v/c T0 COBE (1992) v = 371 +/- 0.5 km/s Temperature fluctuations 1 / 1000

  30. Brief History Photons hot enough to ionize H Compton Scattering couples g to e, and baryons Dynamical system: Baryon-photon Fluid g pressure resists the fluid gravitational compression  acoustic oscillations Recombination: Neutral hydrogen formation and g last scattering Hot (compression) and cold regions  present traces g undergo also a gravitational redshiftfrom the potentials at last scattering. W.Hu

  31. First measurements of CMB anisotropies • Prédictions de Sachs et Wolfe (1967) autour de 10-3, non observées • COBE (1990):around 10-530 mK

  32. Temperature fluctuations • Decomposition in spherical harmonics: • T= (2.725+/-0.01)K + (3.358+/-0.02)mK cosq + S l>1,m alm Ylm • Temperature is real  alm*= alm • Term in l  variation on angular scale Dq = p/ l angle-multipole connexion due to: • + Ylmhas l-m zeros for –1< cosq< 1 • + Re(Ylm) has m zeros for0<F<2p Solar system peculiar velocity

  33. Angular power spectrum • Development in spherical harmonics • Angular Power spectrum l is the inverse of an angle : (Adapted Lineweaver, 1998)

  34. Foreground contaminations Component separation by measurements in different frequencies Theoretical Extrapolation to CMB region Between 100 and 200 GHz !

  35. WMAP Launched june 2001 in space

  36. Wilkinson Microwave Anisotropy Probe David T. Wilkinson 1935-2002 WMAP model WMAP science team http://map.gsfc.nasa.gov/m_mm/pub_papers/firstyear.html 2003

  37. WMAP results Position 2nd peak : l =546 + /-10 Position 1stpeak : l=220.1 +/-0.8 Curve= best fit LCDM

  38. WMAP cosmological parameters (Table I) • LCDM, ie, flat Universe and equation of state w =p/r = cte (= -1) • Measures Wm h2 and Wb h2  fb = Wb/Wm = 0.17 +/-0.02

  39. !!!! WMAP note !!!!! Strong degeneracy in Spergel et al., 2003 ApJS, 148, 175 • WM = 0.47, w=-0.5 and h=0.57 => identical power spectrum • solution excluded for 3 reasons: • 1) h=0.57 2s from HST 2) worse fit SNIa results not true 3) poor fit 2dFGRS galaxy power spectrum surveys Blanchard et al. controversial

  40. 2dfGRS: use of CMB prior

  41. Tegmark et al. astro-ph/0310723 SDSS galaxies power spectrum WM=0.4 h=0.72 =0.5 h=0.56 Baryon fraction • Indication for • Systematics • not cste w? • ? WMAP LCDM h WM

  42. Precision cosmology? Not Just Yet Bridle et al.Science 299(2003) 1532astro-ph 0303180

  43. SNIa: fits with weak priorsWM = 0.30 +/- 0.2 Virey, Ealet, Tao, Tilquin, Bonissent, Fouchez, Taxil astro-ph/0407452 • ~ no prior onWM(flat Universe), eg,WM < 0.60 • other solutions still possible : even decelerating Universes Quintessence Phantom

  44. SN data interpretation needs more precise determinations ofWMor combination with other data Tools existing for each observationeg, CMB: CMBFAST, etc… SNIa: Kosmoshow, Y. Wang, … Weak Lensing, Clusters, … Extraction of cosmological parameters using « priors» on other data Tools needed for combined analysis Attempts: Tegmark & Wang, Corasaniti et al., Padmanabhan et al.,… For different models, eg, with variable w

  45. Combined SN, CMB, WL constraints on equation of state 10% measurement Upadhye , Ishak and Steinhardt, astro-ph 0411803 Future constraints SNAP/JDEM + Planck

  46. “Weak gravitational Lensing” Background image distorsions by foreground matter Without lensing lensing effect

  47. Weak Lensing Distortion Matrix : • Direct measurement of mass distribution in the universe, • Other methods measure light distributions

  48. “Weak Lensing”: principle Distortion Matrix : Convergence: Shear: Critical surface density: Weak lensing regime :  << 1 (linear approximation) Measure shear  and solve for projected mass 

  49. Dark Energy and Weak Lensing w is measurable by WL power spectrum But degeneracy between w, M,8 and  Hui 1999, Benabed & Bernardeau 2001, Huterer 2001, Hu 2000, Munshi & Wang 2002

  50. 4) A closer look at SN measurements

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