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“The present and next generation of large galaxy surveys”

“The present and next generation of large galaxy surveys”. Bob Nichol ICG, Portsmouth. Thanks to all my collaborators on SDSS, DES, WFMOS teams. Outline. A brief overview of Dark Energy Do we believe it? (ISW) How do we measure it better? SDSS SNe Baryon acoustic oscillations (BAO)

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“The present and next generation of large galaxy surveys”

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  1. “The present and next generation of large galaxy surveys” Bob Nichol ICG, Portsmouth Thanks to all my collaborators on SDSS, DES, WFMOS teams

  2. Outline • A brief overview of Dark Energy • Do we believe it? (ISW) • How do we measure it better? • SDSS SNe • Baryon acoustic oscillations (BAO) • Future experiments

  3. Brief Review of Evidence for Dark Energy(circa 2003) Marseille 2006

  4. Largest oscillations that are causally connected

  5. SNe and CMB force us into a Universe ~75% DE and ~25% DM. But is it true and what is DE? SN CMB (DARK) ENERGY Parameterize our ignorance using equation of state W(z) = p (DARK) MATTER

  6. Understanding Dark Energy (The billion dollar question) To confirm DE we need to observe it in as many ways as possible, but there are only two broad avenues: • Geometrical tests (distances, volumes) • Growth of structure (cluster counts) To determine what DE is, we can make progress on two simple 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) No compelling theory, so must be observational driven Marseille 2006

  7. DE require “big surveys” The effect of DE is only seen on large scales, therefore we need to study large volumes to beat “cosmic variance” DE is a small effect (even on large scales) so need large samples to control statistical and systematic errors We need to understand the redshift evolution of DE (w(z)) We need to measure DE using different methods to understand physics of DE and break degeneracies Challenge to experimentalists to build massive surveys (in size and number) with high precision Marseille 2006

  8. “Massive Surveys” SDSS: first “massive” survey SDSSII SNe Baryon Acoustic Oscillations (BAO) ISW DES: next “massive” imaging survey The power of photo-z’s WFMOS: next “massive” redshift survey The power of spectroscopy Marseille 2006

  9. First, do we believe it? Marseille 2006

  10. Integrated Sachs Wolfe (ISW) Physical detection of Dark Energy: Effecting the growth of structure In a flat matter-dominated universe, the gravitational potential of large-scale fluctuations remain constant with time

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

  12. LRG selection 5300 sq degrees Achromatic (no contamination) 5 overall Look for ISW at high redshift using SDSS QSOs Detection of DE at z=1.5 Rule out Phantom models ISW Detected Giannantonio et al. 2006

  13. How do we measure it Better? Marseille 2006

  14. SDSS(z~0 universe) DR4: 849k spectra, 6670 sq degs Done 07/2005: ~700,000 redshifts, 8000 sq degs Extension (2005-2008): Legacy, SNe, Galaxy

  15. SDSSII SNe SurveyExploring DE & SNe at an epoch when DE dominates • Type Ia supernovae (SNe) • spectroscopically confirm and obtain “well-measured” light curves of ~500 SN Ia from z = 0.05 to ~ 0.4 • bridge low-z (z<0.05; LOSS, SNF) and high-z (0.3<z<1.0; ESSENCE, SNLS) sources • understand and minimize systematics of SN Ia as distance indicators (look at correlations with host galaxy properties) • Measure low redshift SNe rate Riess et al. (2004) compilation 9% measurement of w by 2008 comparable with SNLS 6% measurement of w when combined with SNLS Marseille 2006 Astier et al. (2005)

  16. Survey Area N S Use the SDSS 2.5m telescope • September 1 - November 30 of 2005-2007 • Scan 300 square degrees of the sky every 2 days Marseille 2006

  17. Photometric Typing • Color-type SNe candidates using nightly g r i data • fit light-curve for redshift, extinction, stretch for Ia • Able to type with >90% efficiency after ~2 - 4 epochs SN2005hy Ia II Ia II Marseille 2006

  18. Results from 2005 • 130 spectroscopically confirmed SN Ia • 10 spectroscopically probable SN Ia • 6 SN Ib/c (3 hypernovae) • 10 SN II (4 type IIn) • 5 AGN • 150 unconfirmed SNe Ia’s with good light curves (galaxy redshifts for 25 exist) <z> = 0.21 Europe leading the way in 2006 with 17 nights on NTT Marseille 2006

  19. 2005 spectroscopically confirmed + probable SN Ia Marseille 2006

  20. Excess of galaxies separated by 500 million light years BAO Cosmology z~1000 Eisenstien et al. 2005 z~0.35 LRG Marseille 2006

  21. Looking back in time in the Universe CMB SDSS GALAXIES FLAT GEOMETRY FLAT GEOMETRY Marseille 2006 CREDIT: WMAP & SDSS websites

  22. Looking back in time in the Universe Looking back in time in the Universe CMB SDSS GALAXIES FLAT GEOMETRY OPEN GEOMETRY Marseille 2006 CREDIT: WMAP & SDSS websites

  23. Looking back in time in the Universe Looking back in time in the Universe CMB SDSS GALAXIES FLAT GEOMETRY CLOSED GEOMETRY Marseille 2006 CREDIT: WMAP & SDSS websites

  24. UNIVERSE IS FLAT TO 1% PRECISION(Eisenstein et al. 2005) Still the best measurement even after WMAP3 Marseille 2006

  25. Summary I • ISW detected at several redshifts to z=1.5 and consistent with cosmological constant • ~150 SDSS SNIa’s so far, 500 by 2007. Systematics limited and will deliver w to 6% • BAO have been detected to 99.X% and deliver consistent wiggles to WMAP3 for m=0.2XX Marseille 2006

  26. Future Experiments Marseille 2006

  27. Dark Energy Survey (DES) • 5000 sq deg multiband (g,r,i,z) survey of SGP using CTIO Blanco with a new wide-field camera • 40 sq deg time domain search for Sne • Cluster counts from optical+SPT • Weak lensing maps • SNe Ia distance measurement study from 2000 Sne • Unable to gain spectroscopic follow-up for all these Sne. Must use photometric classifications and redshifts • Use SDSSII as a “training sample” to prepare for DES • Galaxy angular power spectrum for 300 million galaxies • Baryon Acoustic Oscillations from photo-z’s Each will independently constrain the dark energy eqn of state <10% DES on-sky by 2009 Marseille 2006

  28. The Dark Energy Survey UK Consortium (I) PPARC funding: O. Lahav (PI), P. Doel, M. Barlow, S. Bridle, S. Viti, J. Weller (UCL), R. Nichol (Portsmouth), G. Efstathiou, R. McMahon, W. Sutherland (Cambridge), J. Peacock (Edinburgh) Submitted a proposal to PPARC in February 2005 requesting £ 1.5 M for the DES optical design. In March 2006, PPARC Council announced that it“will seek participation in DES”. (II) SRIF3 funding: R. Nichol, R. Crittenden, R. Maartens, W. Percival (ICG Portsmouth) K. Romer, A. Liddle (Sussex) Funding the optical glass blanks for the UCL DES optical work These scientists will work together through theUK DES Consortium and are collaborating with the Spanish DES Consortium

  29. u-band from VST could remove the low-z errors (ugrizJK) DES Photo-z’s Simulated DES DES science relies on good photometric estimates of the 300 million expected galaxies griz grizJK Simulated DES+VISTA Marseille 2006

  30. DES + VISTA + VST • Give photo-z’s to z~2 with  < 0.1 • BAO improves by 50% with VISTA; 15% error on w just the BAO scale • Targets for Gemini, VLT • Overlap with CLOVER, SPT DES + Planck ISW will be better than SNAP for non-constant w models (Pogosian et al. 2005) Marseille 2006

  31. 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 First-light in 2012 ~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 WFMOS Marseille 2006

  32. Distance Scale KAOS purple book (Seo, Eisenstein, Blake, Glazebrook) z~1 survey with 2 million galaxies with twice LRG volume 1% accuracy WFMOS will measure w to <4% and dw/dz to <15% Marseille 2006

  33. Growth of Structure DGP LCDM 7 difference Yamamoto et al. 2006 Marseille 2006

  34. Summary II • Experiments by 2010 will measure w (constant) to a few %, but that doesn’t mean we understand it! • Next generation surveys will probe w(z) and start testing “growth of structure” DE measurements of DE • BAO have been detected to

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