probes of dark energy
DESCRIPTION
Probes of Dark Energy. Cluster/Halo abundances volume, structure growth Galaxy Clustering standard rulers, structure Type Ia Supernovae standard candles Weak Lensing geometry, structure Complementarity: of systematic errors and of cosmological - PowerPoint PPT PresentationTRANSCRIPT
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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
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Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004Refregier
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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
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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
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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
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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
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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
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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
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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)
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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
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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
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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%
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Josh Frieman for the DES Collaboration BIRP Meeting, August 12, 2004Riess, etal
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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
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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
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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
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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.