Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Probes of Dark Energy

Cluster/Halo abundances volume, structure growthGalaxy Clustering standard rulers, structure Type Ia Supernovae standard candles Weak Lensing geometry, structure

Complementarity: of systematic errors and of cosmological parameter degeneracies

Our collaboration has substantial, practical experience in all 4 key project areas

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004Refregier

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

DES Weak Lensing

• Measure shapes for ~300 million

source galaxies with z = 0.7

• Shear-shear & galaxy-shear

correlations probe distances &

growth rate of perturbations

• Mass Power spectrum determined

by CMB (WMAP)

Marginalized 68% CL DES constraints

Sky area, depth, photo-z’s, image quality & stability

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Evolution of Dark Energy

• Planck CMB priors

• Cosmic shear to l=3000

• Galaxy-shear to l=1000

• Lens galaxies in halos above 1012.5 Msun in bins of z=0.1 to z=1

• Source galaxies in bins of z=0.28 to z=1.1 plus 1 high-z bin

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Weak Lensing Systematics

• Residual PSF anisotropy (telescope, atmosphere)

• Optical design --> PSF map• Pixel size requirement• Systematic Photo-z errors

(under study)

Refregier

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Cluster WeakLensing MassMap(BTC on Blanco)

Optical survey independently calibrates SZcluster mass estimates through WL and richness

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Type Ia SNeas calibrated`Standard’ Candles

Peak brightnesscorrelates with decline rate(Phillips)

After correction, dispersion in peak brightness ~ 0.12-0.15 mag

Lum

inos

ity

Time

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Type Ia SupernovaeAdvantages:• small dispersion in peak brightness (std. candles)• single objects (simpler than galaxies) • can be observed over wide redshift range (bright)

Challenges/Systematic concerns:• dust extinction in host galaxy• chemical composition variations/evolution• evolution of progenitor population• photometric calibration• Malmquist bias• environmental differences• K correction uncertainties

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

DES Supernovae• Repeat observations of 40 deg2 , 10% of

survey time

• ~1900 well-measured riz SN Ia lightcurves, 0.25 < z < 0.75

• Larger sample, improved z-band response compared to ESSENCE, CFHTLS

• Combination of spectroscopic (~25%) and photometric redshifts

• Develop color typing and SN photo-z’s (critical for LSST)

DES constraints (assuming = 0.2 mag)

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

• Connecting Quarks with the Cosmos, Beyond Einstein, Quantum Universe, Physics of the Universe, HEPAP, DOE OS Facility Plan, …

• All identified Dark Energy as one of the most profound questions in fundamental physics, ripe for experimental progress

• Endorsed a multi-pronged approach to dark energy from ground- and space-based telescopes

• To make progress in understanding Dark Energy, we must reach greater precision: determine DE, w = p/, and its evolution

The Dark Energy Survey in Context

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

• Coherent program aimed at increasing Dark Energy precision over the next ~15 years desirable

• Sequence of logical, incremental steps of increasing scale, technical complexity, and scientific reach

• Increase precision in w from ~20% today* to ~ few % (robustly) over this period. Determine evolution dw/dz to ~20% (current constraints very weak).

• DES as logical next step in Dark Energy measurements beyond current surveys

*Note: all quoted (1) errors on w assume it does not evolve (and beware priors)

The Dark Energy Survey in Context:Toward A U.S. Dark Energy Program

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Dark Energy: where we are now (w) ~ 0.15*, w < –0.76 (95%)

assuming w = –1assuming w constant Tegmark, etal

95% constraints

Key priors: scale-free spectrum, no

gravity waves, massless neutrinos, simple bias Additional prior: flat Universe

*from CMB+LSS+SNe; no single dataset constrains w better than ~30%

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004Riess, etal

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Dark Energy: 2004-2008 (w) ~ 0.1*

• Supernovae:

ESSENCE, CFHTLS, HST, SNF, SDSS,…

many 100’s of SNe Ia over z ~ 0.1-0.8

• Weak Lensing:

Deep Lens, CFHTLS, RCS II, …

~200-1000 sq. deg. deep multi-band imaging

• Cluster SZ:

APEX, ACT, SPT,… ~200 --> 4000 sq. deg.

*SNE+WMAP combined

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

Logical next step in dark energy measurements:• Will measure w to ~ 0.05–0.15 statistical accuracy* using

multiple complementary probes, and begin to constrain dw/dz

• Scientific and technical precursor to the more ambitious Dark Energy projects to follow: LSST and SNAP

• DES in unique position to synergize with SPT on this timescale

• Cannot be done with any existing facility: Blanco+DECAM ~5 times faster survey instrument than CFHT+Megacam, >10x faster than any current U.S. facility, ~2x faster than PanSTARRS I

• Complementarity: DUO (X-ray Clusters), KAOS

*accuracy on each probe separately, with at most weak priors

The Dark Energy Survey in Context:2009-2013

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

• • Ground: LSST Dedicated 8m telescope with wide FOV imager

• Space: JDEM 2m optical/NIR wide-field telescope in space

• Goals: w to few %, dw/dz to ~20%

• Designed as `ultimate’ Dark Energy experiments, they must have exquisite control of systematic errors to reach the next level of cosmological precision

• Timescales and costs reflect this

Dark Energy: 2012/3 and Beyond

Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004

A National Wide-Field Imaging Facility

• Blanco+DECAM will be a unique resource for the astronomy community.