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Dark Energy & LSS

Dark Energy & LSS. SDSS & DES teams (Bob Nichol, ICG Portsmouth). Marie Curie (EC). Dark Energy 1998-2003. Key evidence CMB (   +  M =1) SNIa’s (   > M ) LSS (  M <1). w = P /r. Dark Energy >2004. Observers Prospective. We can make progress on questions:

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Dark Energy & LSS

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  1. Dark Energy & LSS SDSS & DES teams (Bob Nichol, ICG Portsmouth) Marie Curie (EC)

  2. Dark Energy 1998-2003 • Key evidence • CMB (+M=1) • SNIa’s (>M) • LSS (M <1) w = P/r

  3. Dark Energy >2004 Observers Prospective • We can make progress on questions: • Is DE just a cosmological constant (w(z)=-1)? • (Make better observations and push to higher z) • Is DE a new form of matter (with negative effective pressure) or a breakdown of GR? • (Study DE using different probes) • But there are only two broad avenues: • Geometrical tests (SN, BAO) • Growth of structure (ISW, lensing, clusters) No compelling theory, must be observational driven

  4. Massive Surveys Need large surveys of the Universe to measure DE accurately SDSS www.sdss.org/dr6790860 gal, 8417 deg2, 1271680 spectra

  5. How do we use this LSS to probe DE? ISW & BAO Subbarao

  6. Integrated Sachs-Wolfe Effect Dark Energy effects the rate of growth of structure in Universe • Poisson equation with dark energy: • In a flat, matter-dominated universe, then density fluctuations grow as: • Therefore, curvature or DE gives a change in the gravitational potential Wayne Hu

  7. Experimental Set-up Nolta et al, Boughn & Crittenden, Myers et al, Afshordi et al, Fosalba et al., Gaztanaga et al., Rassat et al.

  8. WMAP-SDSS Correlation No signal in a flat, matter-dominated Universe WMAP W band Luminous Red Galaxies (LRGs)

  9. ISW Detected at 4.3s Giannantonio et al. (2008) paper (see also Ho et al. 2008)

  10. Cosmological Constraints See effect of DE to z>1 (10 Gyrs) Flat LCDM Strongest constraint on Wm = 0.2+0.06-0.05 Wm > 0.1 Flat wCDM Matter-dominated models ruled out to high significance

  11. Cosmological Constraints II cs2 = dP/dr

  12. LCDM DGP Modified Gravity Song et al. (2006)

  13. Dark Energy Survey Stage III DE survey • Blanco 4m • 5000 deg2 • ugrizJHK (VISTA=VST) • s < 0.1 to z>1 • Multiple probes • Factor 5 improvement DES ISW will be competitive with SNAP for non-constant w (Pogosian et al. 2005)

  14. Baryon Acoustic Oscillations baryons photons Initial fluctuation in DM. Sound wave driven out by intense pressure at 0.57c. Courtesy of Martin White

  15. Baryon Acoustic Oscillations baryons photons After 105 years, we reach recombination and photons stream away leaving the baryons behind Courtesy of Martin White

  16. Baryon Acoustic Oscillations baryons photons Photons free stream, while baryons remain still as pressure is gone Courtesy of Martin White

  17. Baryon Acoustic Oscillations baryons photons Photons almost fully uniform, baryons are attracted back by the central DM fluctuation Courtesy of Martin White

  18. Baryon Acoustic Oscillations baryons photons Fourier transform gives sinusoidal function Today. Baryons and DM in equilibrium. The final configuration is the original peak at the center and an echo roughly 100Mpc in radius Courtesy of Martin White

  19. Baryon Acoustic Oscillations Many superimposed waves. See them statistically • Positions predicted once (physical) matter and baryon density known - calibrated by the CMB. • Oscillations are sharp, unlike other features of the power spectrum Daniel Eisenstein

  20. Looking back in time in the Universe CMB SDSS GALAXIES FLAT GEOMETRY CREDIT: WMAP & SDSS websites

  21. Looking back in time in the Universe CMB SDSS GALAXIES OPEN GEOMETRY CREDIT: WMAP & SDSS websites

  22. Looking back in time in the Universe CMB SDSS GALAXIES CLOSED GEOMETRY CREDIT: WMAP & SDSS websites

  23. Baryon Acoustic Oscillations m=0.24 best fit WMAP model Miller et al. 2001, Percival et al. 2001, Tegmark et al. 2001, 2006 Cole et al. 2005, Eisenstein et al. 2005, Hutsei 2006, Blake et al. 2006, Padmanabhan et al. 2006 WMAP3 Power spectrum of galaxy clustering. Smooth component removed Percival et al. 2006 SDSS DR5 520k galaxies

  24. Cosmological Constraints Standard ruler (flat,h=0.73,b=0.17) 99.74% detection Percival et al. (2006) h=0.72±0.08 HST m=0.256+0.049-0.029 Best fit m=0.26 Sullivan et al. (2003) m0.275h WMAP3 m=0.256+0.029-0.024 mh2 WMAP3 m=0.256+0.019-0.023

  25. BAO with Redshift Measure ratio of volume averaged distance D0.35 /D0.2 = 1.812 ± 0.060 Flat CDM = 1.67 Systematics (damping, BAO fitting) also ~1Next set of measurements will need to worry about this 99.74% detection z~0.2 143k + 465k 79k z~0.35 Percival et al. (2006) Percival et al. 2007

  26. Cosmological Constraints Flatness assumed, constant w With CMB Only D0.35 /D0.2 W 3 1 Favors w<-1 at 1.4 2 m

  27. Cosmological Constraints Flatness assumed m = 0.249 ± 0.018 w = -1.004 ± 0.089 With CMB Only D0.35 /D0.2 W W 3 1 D0.35 /D0.2 = 1.66 ± 0.01 2 m m

  28. Discrepancy! What Discrepancy? • 2.4 difference between SN & BAO. The BAO want more acceleration at z<0.3 than predicted by z>0.3 SNe (revisit with SDSS SNe) • ~1 possible from details of BAO damping - more complex then we thought • Assumption of flatness and constant w needs to be revisited

  29. N S SDSS SN Survey Use the SDSS 2.5m telescope • September 1 - November 30 of 2005-2007 • Scan 300 square degrees of the sky every 2 days • 500 spectroscopically confirmed Ia’s at z<0.4, many more photometrically classified

  30. SDSS SN Constraints Preliminary Preliminary

  31. DE Constraints

  32. Measure distance to ~1% at z=0.35 and z=0.6 10000 deg2 with 1.5m LRGs to 0.2<z<0.8 160k quasars at 2.3<z<2.8 h to 1% with SDSS SNe www.sdss3.org Baryon Oscillation Spectroscopic Survey (BOSS)

  33. Proposed MOS on Subaru via an international collaboration of Gemini and Japanese astronomers 1.5deg FOV with 4500 fibres feeding 10 low-res spectrographs and 1 high-res spectrograph ~20000 spectra a night (2dfGRS at z~1 in 10 nights) DE science, Galactic archeology, galaxy formation studies and lots of ancillary science from database Design studies underway; on-sky by 2013 WFMOS

  34. ISW is detected and delivering ~10% measurementsof parameters; strongest when used in tandem with other observations and for complementary parameters (cs2, MG, curvature) SDSS BAO measures are delivering sub 10% measurements of cosmological parameters 2 discrepancy with SNe? Sign of more complex physics or systematics? WFMOS and SDSS-III will move BAO to 1% level Conclusions

  35. What is Dark Energy?

  36. Redshift and Cadence • 325 spectro Ia’s • 31 spectro probable Ia’s • 80 photo Ia’s with host z • 14 spectro Ib/c • 30 spectro II Interval between observations of same object

  37. SN Rate vs Galaxy Type

  38. CosmologyStill not ready, but close z=0.19 z=0.35 (44) (90) (60) (70) MLCS2k2 i-band causing the problem

  39. DES SN Survey SN surveys are systematics limited Provide a large sample of high-redshift SN Ia (redshift > 0.7) with good rest-frame g-band (observer-frame z-band) light curves . Possible with enhanced red sensitivity of DECam. • 750 hrs time • 9 deg2 • 4 - 6 days in riz • Possible Y • 1400 Ia’s • 0.2 < z < 1

  40. DES SN Survey Spectroscopic Follow-up Focus spectroscopy on 300 Ia’s in elliptical hosts as less dust and no SNII Target high-z clusters Monte Carlos simulations underway Sullivan et al. (2003)

  41. DES SN Survey Forecasts DETF FoM • Well known and proven • Nearly factor of 5 improvement in FoM • These predictions include systematic errors as well

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