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Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy

Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy. Ofer Lahav, University College London. The Dark Energy Survey Photo-z methodology Photo-z and probes Applications: LRGs, DES, DUNE. mainly with Filipe Abdalla and Manda Banerji. Ofer Lahav University College London.

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Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy

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  1. Photo-z for LRGs, DES, DUNE and the cross talk with Dark Energy Ofer Lahav, University College London • The Dark Energy Survey • Photo-z methodology • Photo-z and probes • Applications: LRGs, DES, DUNE mainly with Filipe Abdalla and Manda Banerji Ofer Lahav University College London

  2. “Evidence” for Dark Energy Observational data • Type Ia Supernovae • Galaxy Clusters • Cosmic Microwave Background • Large Scale Structure • Gravitational Lensing Physical effects: • Geometry • Growth of Structure Both depend on the Hubble expansion rate: H2(z) = H20 [M (1+z) 3 + DE (1+z) 3 (1+w) ] (flat)

  3. Dark Energy: back to Newton? F = -GM/r2 + /3 r X * “I have now explained the two principle cases of attraction… which is very remarkable” Newton, Principia

  4. The Future of the Local Universem =0.3 LCDM a = 1 (t= 13.5 Gyr) LCDM a = 6 (t= 42.4 Gyr) OCDM a = 1 (t= 11.3 Gyr) OCDM a = 6 (t= 89.2 Gyr) Hoffman, OL, Yepes & Dover 2007

  5. Survey Filters Depth Dates Status Sq. Degrees CTIO 75 1 shallow published VIRMOS 9 1 moderate published COSMOS 2 (space) 1 moderate complete 36 4 deep complete DLS (NOAO) Subaru 30? 1? deep observing 2005? 170 5 moderate observing CFH Legacy 2004-2008 830 3 shallow approved RCS2 (CFH) 2005-2007 VST/KIDS/ VISTA/VIKING 1700 4+5 moderate 2007-2010? 50%approved 5000 4 moderate proposed DES (NOAO) 2008-2012? Pan-STARRS ~10,000? 5? moderate ~funded 2006-2012? LSST 15,000? 5? deep proposed 2014-2024? 1000+ (space) 9 deep proposed JDEM/SNAP 2013-2018? Imaging Surveys proposed moderate 5000? 4+5 2010-2015? VST/VISTA proposed moderate 2+1? DUNE 20000? (space) 2012-2018? Y. Y. Mellier

  6. Photo-z / Cosmology Synergy Large Scale Structure Photo-z Gravitational Lensing Simulations Clusters of Galaxies

  7. The Dark Energy Survey

  8. The Dark Energy Survey Blanco 4-meter at CTIO • Study Dark Energy using 4 complementary techniques: I. Cluster Counts II. Weak Lensing III. Baryon Acoustic Oscillations IV. Supernovae • Two multi-band surveys 5000 deg2g, r, i, z 40 deg2 repeat (SNe) • Build new 3 deg2 camera and data management system Survey 2010-2015 (525 nights) 300,000,000 photometric redshifts within a volume of 23 (Gpc/h)^3, out to z = 2

  9. DES Organization Over 100 scientists in 17 institutions In the US, UK, Spain and Brazil Science Working Groups Supernovae B. Nichol J. Marriner Weak Lensing B. Jain S. Bridle Galaxy Clustering E. Gaztanaga W. Percival Photometric Redshifts F. Castander H. Lin Simulations Kravtsov A. Evrard Clusters J. Mohr T. McKay DES:UK consortium: UCL, Portsmouth, Cambridge, Edinburgh, Sussex

  10. DES Status • Low-risk, near-term (2010-15) project with high discovery potential • Survey strategy delivers substantial DE science after 2 years • Synergy with SPT and VISTA • Precursor to LSST, DUNE and JDEM • Total cost is relatively modest (~ $20-30M) • STFC approved £1.7M for the DES optical corrector, subject to funding in the US • Glass ordered by UCL in Sep 07 (funds from 5 universities) • DES in the US President budget request for FY08 • DOE CD1 approved; CD2/CD3 in Jan 08 • NSF contribution to data management

  11. DES Forecast Constraints DETF FoM • DES+Stage II combined = Factor 4.6 improvement over Stage II combined • Consistent with DETF range for Stage III DES-like project • Large uncertainties in systematics remain, but FoM is robust to uncertainties in any one probe, and we haven’t made use of all the information

  12. DES Forecasts: Power of Multiple Techniques w(z) =w0+wa(1–a) 68% CL Ma, Tang, Weller FoM factor 4.6 tigther compared to near term projects

  13. Sources of uncertaintiesin measuring Dark Energy • Theoretical (e.g. the cosmological model) • Astrophysical (e.g. galaxy and cluster properties) • Instrumental (e.g. image quality)

  14. Photometric redshifts z=0.1 z=3.7 • Probe strong spectral features (e.g. 4000 break)

  15. Photo-z –Dark Energy cross talk • Approximately, for a photo-z slice: (w/ w) = 5 (z/ z) = 5 (z/z) Ns-1/2 => the target accuracy in w and photo-z scatter z dictate the number of required spectroscopic redshifts Ns =105-106

  16. Cosmology from photo-z surveys • Optimization of Photo-z for cosmic probes • Photo-z mocks and algorithms • Spetroscopic training sets • MegaZ-LRG (DR6) • DES • VISTA • DUNE • other surveys BAO, WL, neutrino mass, ISW, halo parameters,…

  17. Photo-z Challenges • Optimizing hybrid methods - errors - pdf - ‘clippping’ • Optimal filters • Spetroscopic training sets • Field vs cluster photo-z • Synergy with BAO and WL • “Self calibration” and “colour tomography”

  18. Photo-z Methods • Template fitting (e.g. Hyper-z) • Bayesian methods (e.g. BPZ, Zebra) • Training-based methods (e.g. ANNz)

  19. ANNz - Artificial Neural Network Output: redshift Input: magnitudes Collister & Lahav 2004 http://www.star.ucl.ac.uk/~lahav/annz.html

  20. MegaZ-LRG *Training on ~13,000 2SLAQ*Generating with ANNz Photo-z for ~1,000,000 LRGs over 5,000 sq deg, 2.5 (Gpc/h)^3 z = 0.046 Collister, OL et al.

  21. LRG - photo-z code comparison M. Banerji, F. Abdalla F., V. Rashkov, OL et al

  22. photo-z bins Collister et al.

  23. Baryon oscillations from MegaZ-LRG Blake, Collister, Bridle & OL; astro-ph/0605303

  24. Halo fit to MegaZ-LRG Blake, Collister,OL 0704.3377

  25. Excess Power on Large Scales? Blake et al. 06 Padmanabhan et al. 06

  26. The Dark Energy Survey

  27. DES (5 filters) vs. DES+VISTA(8 filters) DES+VISTA would improve photo-z by a factor of 2 for z> 1 What is the effect on WL, BAO, SNIa Science? Banerji, Abdalla, OL, Lin et al.

  28. DES+VISTA: Galaxy Power Spectrum For the same clipping threshold, we can measure the power spectrum accurately to higher redshifts using the DES+VISTA data. DES grizY DES grizY + VISTA JHK

  29. DES+VISTA : Effect of Reddening Plots generated using JPL mocks (P.Capak) which include the effects of reddening

  30. DES z=0.8 photo-z shell   Back of the envelope: improved by sqrt (volume) => Sub-eV from DES (OL, Abdalla, Black, Kiakotou; in prep)

  31. DUNE: Dark UNiverse Explorer • Mission baseline: • 1.2m telescope • FOV 0.5 deg2 • PSF FWHM 0.23’’ • Pixels 0.11’’ • GEO (or HEO) orbit • Surveys (3-year initial programme): • WL survey: 20,000 deg2 in 1 red broad band, 35 galaxies/amin2 with median z ~ 1, ground based complement for photo-z’s • Near-IR survey (J,H). Deeper than possible from ground. Secures z > 1 photo-z’s

  32. Optical and Optical+NIR Abdalla, Amara, Capak, Cypriano, OL , Rodes astro-ph/0705.1437

  33. DE FoM for DUNE with and without NIR NIR will improve FoM by 1.3-1.7

  34. DE FOM vs number of spectra needed Abdalla et al.

  35. Photo-z Challenges • Optimizing hybrid methods - errors - pdf - ‘clippping’ • Optimal filters • Spetroscopic training sets • Field vs cluster photo-z • Synergy with BAO and WL • “Self calibration” and “colour tomography”

  36. The END

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