OUTLINE

1. OUTLINE • Science Motivatio n and Methods • Dark Energy via the cluster mass function, weak lensing, SNe, galaxy angular power spectrum • Survey Design • 4-band, 5000 Sq. Degrees • Multiple-pass tilings - - - > towards an LSST data mode • The Instrument • New optics, new detector package • Archive Plans • Context and Status Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

2. MOTIVATION:Dark Energy and Dark Matter Dark Energy is the dominant constituent of the Universe. Dark Matter is next. 95% of the Universe is in Dark Energy and Dark Matter, for which we have little or no detailed understanding. 1998 and 2003 Science breakthroughs of the year Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

3. METHODS:The Cluster Mass Function: Masses N(M,z) is sensitive to dark energy both through the impact of dark energy on the growth of structure, and its effect on dV/dz • Mass Estimators: multiple calibrators • Count galaxies (or luminosity) in a cluster • Weak lensing • Sunyaev-Zeldovich (SZ) • hot electrons in clusters scatter CMB photons; proportional to cluster mass • insensitive to redshift • The South Pole Telescope (SPT) • 4000 sq. deg. survey Southern Galactic cap • measures cluster masses using SZ effect • funded and in construction – first “light” 2006 Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

4. METHODS:The Cluster Mass Function: Redshifts • DES data will enable cluster photometric redshifts with dz~0.02 for clusters out to z~1.3, for all masses relevant to the SPT Survey. • DES main survey will yield photo-z’s on approximately 300 million galaxies extending beyond a redshift of z~1. Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

5. METHODS:Weak Lensing and Galaxy Angular Power Spectrum • Weak Lensing: • Measure shapes for ~300 million source galaxies with z = 0.7 • Direct measure of the distribution of mass in the universe, as opposed to the distribution of light, as in other methods (eg. galaxy surveys) • Galaxy Angular Power Spectrum: • We can study the angular clustering within redshift bins to z~1 • Peak of the angular power spectrum represents a standard rod and hence is a measure of the angular diameter distance to each redshift shell (i.e. Cooray et al 2001). DES constraints from galaxy w0 (Hu 2004) Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

6. METHODS:SN Ia: “Standardizable” Candles • Type Ia Supernovae magnitudes and redshifts provide a direct means to probe dark energy • Standardizable candles • Dark Matter dominates for z> ~0.75 • Dark Energy dominates at low z • DES will make the next step: • Image 40 sq-degree repeatedly • 2000 supernovae at z= 0.3-0.8 • Well measured light curves • photo-z’s for all, + some spectroscopic redshifts (this must work for LSST…) Figure from Riess et al 2004 Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

7. SURVEY DESIGN:The Dark Energy Survey (DES) • Proposal: • Perform a 5000 sq. deg. survey of the southern galactic cap • constrain the Dark Energy parameter w to ~ 5% with 4 complementary techniques • begin to constrain dw/dz • New Equipment: • Replace the PF cage on the CTIO Blanco 4m telescope with a new 2.2 deg. FOV optical CCD camera • Time scale: • Instrument Construction 2005-2009 • Survey: • 30% of the telescope time from 2009-2013 Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

8. SURVEY DESIGN:The Dark Energy Survey (DES) SPT Area Tie region SDSS Stripe 82 Science Program Survey Description • Survey Basics: • Survey Area 5000 sq. deg. in Southern Galactic Cap with connection to SDSS stripe 82 for photo-z calibration • SDSS g,r,i,z :10 Limiting mag: 24.6, 24.1, 24.3, 23.9 • Primary: Multiple tilings (5+) in nominally 100sec units • Secondary: 40 deg2 synoptic Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

9. SURVEY DESIGN:Critical Cluster Complementarity • Combination of SPT mass measurements and DES redshifts place joint constraints on w and Wm : • Fiducial cosmology parameters from WMAP: s8=0.84, Wm=0.27, w = -1 • 29000 clusters in the 4000 deg2 DES+SPT survey area • Curvature free to vary (dashed); one sigma uncertainty on w is 0.071 • Curvature fixed @ 0 (solid); one sigma uncertainty on w is 0.04 DES + SPT: Majumdar & Mohr 2003 SNAP: Perlmutter & Schmidt 2003 WMAP: Spergel et al 2003 Parameter degeneracies are complementary Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

10. 3556 mm Camera 1575 mm Shutter Filters 2.2 deg. FOV Corrector Cage THE INSTRUMENT:The Dark Energy Camera (DECam) Survey Description  Instrument Design • Instrument Basics: • 3 sq-degree camera with ≥ 2.2 deg FOV • 62 CCDs, 2kx4k – 0.5G pixel focal plane • SDSS g,r,i,z filters • Pixel size 15 microns, 0.27” /pix • Readout time ~17 sec. Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

11. THE INSTRUMENT:Corrector and Focal Plane • 2.2 Degree Corrector: • 5-element fused-silica,1 asphere • scroll shutter + flip filter (4 loaded) • excellent images: 0.22” RMS, <0.38” • low distortion <1% • explicit control of ghosting • Focal Plane: • 62 2k x 4k CCDs for main image, 4-side buttable, 15 micron pixels • 8 1k x 1k guide and focus CCDs • baseline LBNL ultra-red chips Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

12. ARCHIVE PLANS: • Data Archive: • Automatic ingest of data from CTIO • Pipeline processing using thoroughly vetted pipelines – data “challenges” developed as part of simulation effort: build effort on pipelines and data management commensurate with instrument build effort • Fast re-processing supported via the Grid • Public data access supported using search and retrieval tools baselined on existing projects • Single pointing images released ~1 year after acquisition • Science products (processed and mosaiced images, and object catalogs) released twice, at the midway point and the end of the survey Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

13. CONTEXT AND STATUS:A Near-Term Dark Energy RoadMap Present to 2008:(w) ~ 0.1 (SNE+WMAP combined , ~0.3 alone) Dark Energy Survey: 2009-2013 • Will measure w using multiple complementary probes with statistical accuracy*: • Cluster counts: (w) ~ 0.05 • Weak lensing: (w) ~ 0.05 • Angular power spectrum: (w) ~ 0.10 • SN Ia : (w) ~ 0.15 • *statistical accuracy on each probe separately, with at most weak priors • DES will be in a unique position to provide constraints on the Dark Energy parameter w and start to constrain the time evolution dw/dz • DECam will be a community instrument, with up to 70% of CTIO time available to the community even during DES operations Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO

14. CONTEXT AND STATUS:Next Steps for DES • A Joint DOE-NSF Program: • Fermilab has given Stage I approval of the DES. • Fermilab Stage II approval is contingent on several criteria, and a review process in 2005. The DES has asked Fermilab and the university partners to fund 80% of the instrument costs. • NOAO’s external BIRP panel was presented with the DES project in August and has recommended awarding of 525 nights in 2009-2013, contingent upon delivery of a complete instrument and archive package. • The DES plans to submit a multi-disciplinary proposal to the NSF to fund the data management, the archive, and 20% of the instrument costs. Mike Gladders for the DES Collaboration; LSST Meeting, September 21, 2004, Seattle, WA Fermilab, U. Illinois, U. Chicago, LBNL, CTIO/NOAO