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Dark Energy Survey

Dark Energy Survey. The DES Collaboration Josh Frieman, Ofer Lahav, JW. Fermilab: J. Annis, H. T. Diehl, S. Dodelson, J. Estrada, B. Flaugher, J. Frieman, S. Kent, H. Lin, P. Limon, K. W. Merritt, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker, W. Wester

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Dark Energy Survey

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  1. Dark Energy Survey The DES CollaborationJosh Frieman, Ofer Lahav, JW

  2. Fermilab:J. Annis, H. T. Diehl, S. Dodelson, J. Estrada, B. Flaugher, J. Frieman, S. Kent, H. Lin, P. Limon, K. W. Merritt, J. Peoples, V. Scarpine, A. Stebbins, C. Stoughton, D. Tucker, W. Wester University of Illinois at Urbana-Champaign:C. Beldica, R. Brunner, I. Karliner, J. Mohr, R. Plante, P. Ricker, M. Selen, J. Thaler University of Chicago:J. Carlstrom, S. Dodelson, J. Frieman, M. Gladders, W. Hu, S. Kent, A. Kravtsov, E. Sheldon, R. Wechsler Lawrence Berkeley National Lab:G. Aldering, N. Roe, C. Bebek, M. Levi, S. Perlmutter NOAO/CTIO:T. Abbott, C. Miller, C. Smith, N. Suntzeff, A. Walker Institut d'Estudis Espacials de Catalunya:F. Castander, P. Fosalba, E. Gaztañaga, J. Miralda-Escude Institut de Fisica d'Altes Energies:E. Fernández, M. Martínez University College London:O. Lahav, P. Doel, M. Barlow, S. Bridle, S. Viti, S. Warwick, J. Weller University of Cambridge:G. Efstathiou, R. McMahon, W. Sutherland University of Edinburgh:J. Peacock University of Portsmouth:R. Nichol University of Michigan:R. Bernstein, B. Bigelow, M. Campbell, A. Evrard, D. Gerdes, T. McKay, M. Schubnell, G. Tarle, M. Tecchio The DES Collaboration

  3. Dark Energy: Stress Energy vs. Modified Gravity Stress-Energy: G = 8G [T(matter) + T(dark energy)] Gravity: G + f(g) = 8G T(matter) Key Experimental Questions: Is DE observationally distinguishable from a cosmological constant, for which T (vacuum) = g/8G? To decide, measure w: what precision is needed? Can we distinguish between gravity and stress-energy? If w 1, it likely evolves: how well can/must we measure dw/da to make progress in fundamental physics?

  4. comoving distance • standard candles • standard rulers • volume factor • growth of structure depends on H(z) probed with power spectrum Probing Dark Energy with the Expansion History of the Universe

  5. The Dark Energy Survey Blanco 4-meter at CTIO • Study Dark Energy using 4 complementary* techniques: Cluster counts & clustering Weak lensing Galaxy angular clustering SNe Ia distances • Two multiband surveys: 5000 deg2g, r, i, z 40 deg2 repeat (SNe) • Build new 3 deg2 camera Construction 2005-2009 Survey 2009-2014 (525 nights) *in systematics & in cosmological parameter degeneracies *geometric+growth: test Dark Energy vs. Gravity

  6. The DES Telescope • NOAO/CTIO 4m Blanco telescope • 1970 era, equatorial mount • An existing, working telescope • On-going studies: finite element analysis, laser metrology, PSF pattern modeling • Solid primary mirror • 50cm thick Cervit, 15 tons • Mechanical mirror support system • radial: purely mechanical • axial: 3 load cell hard points + controllable support cells • Primary cage • DES will replace entire cage • will have radial (alignment) movement • Cerro Tololo • site delivers median 0.65” Sept-Feb • current Mosaic II+telescope delivers median 0.9” Sept-Feb 3 Hard Points Abbott, Walker, Peoples, Bernstein... 24 RadialSupports 33 Pressure Pads

  7. Dark Energy Survey Instrument 3.5 meters Camera 1.5 meters Scroll Shutter Filters Optical Lenses New Prime Focus Cage, Camera, and Corrector for the Blanco 4m Telescope 500 Megapixels, 0.27”/pixel Project cost: ~20M$ (incl. labor)

  8. Photometric Redshifts • Measure relative flux in four filters griz: track the 4000 A break • Estimate individual galaxy redshifts with accuracy (z) ~ 0.1 (~0.02 for clusters) • This is sufficient for Dark Energy probes (biases ?) • Note: good detector response in z band filter needed to reach z~1.3

  9. Seeing Issues * Seeing affects the number of galaxy images ‘usable’ for lensing • ‘Seeing’ is due to intrinsic PSF, telescope flexure, atmospheric turbulence the dome,… • Recent records for medians • @ CTIO site 0.67 arcsec during Sep-Feb; @ Blanco Mosaic II 0.9 arcsec Efforts to reduce it!

  10. Improved Optical Image Quality of DECAM vs. Mosaic II • Focus and wavefront sensor chips: actively correct focus and collimation • New optical corrector designed to deliver good image quality • over FOV and won’t be cracked • Reduce power dissipation in vicinity of camera • Precision focal plane alignment • Model and track PSF vs. focal plane position, zenith angle (refraction), • defocus, decollimation • Typical object will be imaged ~24 times in riz and enough • survey time to use best conditions for WL • Gladders, Kent

  11. DES Area and Depth: Synergy with South Pole Telescope • South Pole Telescope: • 4000 sq. deg. survey • Detect ~20,000 clusters through Sunyaev-Zel’dovich effect • Dark Energy Survey: measure photometric redshifts for these clusters to z ~ 1-1.3: griz ~ 24 Galactic Dust Map

  12. 10m South PoleTelescope (SPT)and 1000 Element Bolometer Array • Low noise, precision telescope • 1.0 arcminute • 3 levels of shielding • ~1 m radius on primary • inner moving shields • outer fixed shields SZE and CMB Anisotropy - 4000 sq deg SZE survey - deep CMB anisotropy fields - deep CMB Polarization fields People Carlstrom (UC) Holzapfel (UCB) Lee (UCB,LBNL) Leitch (UC) Meyer (UC) Mohr (U Illinois)Padin (UC) Pryke (UC) Ruhl (CWRU) Spieler (LBNL) Stark (CfA) 1000 Element Bolometer Array - 3 to 4 interchangeable bands (90) 150, 250 & 270 GHz

  13. Raisingwat fixed WDE:  decreases volume surveyed Volume effect Growth effect Cluster Redshift Distribution and Dark Energy Constraints: •  decreases growth rate of • density perturbations Mohr

  14. Requirements Quantitative understanding of the formation of dark matter halos in an expanding universe Clean way of selecting a large number of massive dark matter halos (galaxy clusters) over a range of redshifts Redshift estimates for each cluster (photo-z’s adequate) Observables that can be used as mass estimates at all redshifts Sensitivity to Mass Cosmology with Clusters Jenkins, et al

  15. SZE vs. Cluster Mass: Simulations Integrated SZE flux decrement insensitive to gas dynamics in the cluster core Motl, et al

  16. Flux decrement vs. mass and redshift Nagai - astro-ph/0512208 11 clusters; ART (Kravtsov) shifted for clarity blue: star formation, metal enrichment and thermal feedback due to the supernovae type II and type Ia, self-consistent advection of metals, metallicity dependent radiative cooling and UV heating due to cosmological ionizing background

  17. DES Cluster Photometric Redshift Simulations (z)~0.02 to z=1.3

  18. Self-calibration with Clustering 1 wa -1 Hu Lima and Hu See also Battye and Weller, Majumdar & Mohr

  19. Mapping the Mass in a Cluster of Galaxies via Weak Gravitational Lensing (no arcs) Abell 3667 CTIO 4-m image Joffre, etal

  20. Calibration of the Mass - Temperature Relation with Weak Lensing (Dodelson & Weller, in preparation)

  21. Background sources Overdensities Observer • Statistical measure of shear pattern, ~1% distortion. • Radial distances, r(z), depends on geometry of Universe. • Dark Matter pattern & growth depends on cosmological parameters.

  22. Lensing Tomography Shear at z1 and z2 given by integral of growth function & distances over lensing mass distribution. zl1 zl2 z1 lensing mass z2

  23. DES Weak Lensing Tomography • Measure shapes for ~300 million source galaxies with z = 0.7 • Shear-shear & galaxy-shear correlations probe distances & growth rate of perturbations • Requirements: Sky area, depth, photo-z’s, image quality & stability Huterer

  24. Galaxy Photo-z Simulations DES griz filters 10 Limiting Magnitudes g 24.6 r 24.1 i 24.0 z 23.9 +2% photometric calibration error added in quadrature (z)~0.1 to z~1.3 Cunha, Lima, Oyaizu, Lin, Frieman, Collister, Lahav

  25. Galaxy Photo-z Simulations DES + VISTA griz+YJHKs filters 10 Limiting Magnitudes Y 22.45 J 22.15 H 21.65 Ks 21.15 (~15 min exposures) (z) ~ 0.07

  26. Impact of Uncertainty in Photo-z Error Distribution on w Spectroscopic `Training Set’ needed to measure photo-z error distribution to required accuracy: N ~ 50,000 - 100,000 Ma, Hu, & Huterer (2005)

  27. DES Supernovae z=0.1 bins assumed • Repeat observations of 40 deg2 , 10% of survey time • ~1900 well-measured riz SN Ia lightcurves, 0.25 < z < 0.75 SN constraints `orthogonal’ to the other methods Huterer

  28. Forecast DES Constraints on w Key Priors: • Constant w, spatially flat, power-law, adiabatic, Gaussian initial fluctuations,w/ CDM, massless neutrinos • Marginalize over 3-parameter SZ(M) with no scatter • 5 halo model bias parameters per photo-z bin • WL: l<1000 • SN: sys. error floor, (m)=0.25, 300 low-z SNe to anchor Hubble diagram Flaugher, Walker, Abbott...

  29. Dark Energy: 2009-2014 DES+SPT next step in dark energy measurements: • Will measure constant w to ~ 0.02–0.1 statistical accuracy* using multiple complementary probes, and begin to constrain dw/dz • Survey strategy delivers substantial DE science after 2 years • Scientific and technical precursor to the more ambitious and costly Dark Energy projects to follow: LST and JDEM • DES in unique position to synergize with SPT on this timescale *accuracy on each probe separately, with Planck priors

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