Transcript The Dark Energy Survey and the Need for DECam Josh Frieman DES Project Director Fermilab and University of Chicago DES/DECam Dedication CTIO November 9, 2012

The Dark Energy Survey and
the Need for DECam
Josh Frieman
DES Project Director
Fermilab and University of Chicago
DES/DECam Dedication
CTIO
November 9, 2012
Dark Energy
• Discovery of Cosmic Acceleration in 1998
Subsequent decade: confirmation of the discovery (Nobel Prize 2011)
• Coming decade(s): what physics causes cosmic acceleration?
Dark Energy or Modification of General Relativity? Cosmological constant?
• Requires new, powerful surveys: multiple probes of the history of
cosmic expansion and of the growth of large-scale structure
DES Genesis
• Conceived in early 2003 as optical follow-up for the South Pole
Telescope (SPT)
Provide photometric redshifts for SPT clusters found via the SunyaevZel’dovich (SZ) effect, enabling cluster probe of Dark Energy
• Early discussions at UIUC, U Chicago (KICP), and Fermilab
 Joe Mohr, Jim Annis, JF
 Wide, deep survey would require new instrument
 Discussions with UK about reviving optical imager for VISTA 4m (ESO)
• NOAO Announcement of Opportunity for wide-field instrument
for the CTIO 4-meter (Blanco) in Dec. 2003: perfect match!
• UIUC, FNAL, UC, LBNL formed collaboration to respond, with
John Peoples as Director
• Science case broadened from SPT clusters to 4 DE probes
 Clusters, Weak Lensing, Supernovae, Large-scale structure
• DES Proposal accepted by NOAO Sept. 2004, partnership
formed with CTIO and thereafter built international collaboration
The DES Collaboration
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Fermilab
University of Illinois at Urbana-Champaign/NCSA
Over 130 members
University of Chicago
plus students &
Lawrence Berkeley National Lab
postdocs
NOAO/CTIO
DES Spain Consortium
Funding: DOE, NSF;
DES United Kingdom Consortium
UK: STFC, SRIF;
University of Michigan
Spain Ministry of
Ohio State University
Science, Brazil:
University of Pennsylvania
FINEP, Ministry of
DES Brazil Consortium
Science, FAPERJ;
Argonne National Laboratory
Germany: Excellence
SLAC-Stanford-Santa Cruz Consortium
Cluster; collaborating
Universitats-Sternwarte Munchen
institutions
Texas A&M University
ETH-Zurich
plus Associate members at: Brookhaven National Lab,
U. North Dakota, Paris, Taiwan
The Dark Energy Survey
• Survey project using 4
complementary techniques:
I. Cluster Counts
II. Weak Lensing
III. Large-scale Structure
IV. Supernovae
• Two multiband imaging surveys:
5000 deg2 grizY to 24th mag
30 deg2 repeat griz (SNe)
• New 3 deg2 FOV camera
and Data management system
Survey 2012-2017 (525 nights)
Facility instrument for Blanco
www.darkenergysurvey.org
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Photometric Redshifts
Elliptical galaxy spectrum
• Measure relative flux in
multiple filters:
track the 4000 A break
• Estimate individual galaxy
redshifts with accuracy
(z) < 0.1 (~0.02 for clusters)
• Precision is sufficient
for Dark Energy probes,
provided error distributions
well measured.
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Clusters
Number of clusters above mass threshold
•Clusters are proxies for massive
dark matter halos and can be
identified optically to redshifts z>1
• Galaxy colors provide
photometric redshift estimates for
each cluster
• Observable proxies for cluster
mass: optical richness (DES), SZ
flux decrement (SPT), weak
lensing mass (DES)
Dark Energy
equation of state
dN(z)
dV

n z
dzd dzd

Mohr
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Volume
Growth
Synergy with South Pole Telescope
DES footprint: 5000 sq deg
DES survey area encompasses SPT Sunyaev-Zel’dovich Cluster Survey
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Synergy with South Pole Telescope
DES footprint: 5000 sq deg
SPT survey
Area:
2500
sq deg
DES survey area encompasses SPT Sunyaev-Zel’dovich Cluster Survey
SZ flux correlates well with cluster dark halo mass
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Weak Lensing: Cosmic Shear
Dark matter halos
Background
sources
Observer
•
•
•
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Spatially coherent shear pattern, ~1% distortion
Radial distances depend on expansion history of Universe
Foreground mass distribution depends on growth of structure
Weak Lensing Mass and Shear
Weak lensing: shear and mass
Takada
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Large-scale Structure
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LSS: Baryon Acoustic Oscillations
Galaxy angular
power spectrum
in photo-z bins
(relative to model
without BAO)
Fosalba & Gaztanaga
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B. Dilday
Supernovae
SDSS-II: 500 spectroscopically confirmed SNe I
Supernova Hubble Diagram
Kessler et al 2009
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Supernova Hubble Diagram
DES Simulation:
~4000 well-measured
SN Ia light curves
Kessler et al 2009
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DES Science Summary
Four Probes of Dark Energy
• Galaxy Clusters
Current Constraints on DE
Equation of State
• ~100,000 clusters to z>1
• Synergy with SPT, VHS
• Sensitive to growth of structure and geometry
• Weak Lensing
• Shape measurements of 200 million galaxies
• Sensitive to growth of structure and geometry
• Baryon Acoustic Oscillations
• 300 million galaxies to z = 1 and beyond
• Sensitive to geometry
• Supernovae
• 30 sq deg time-domain survey
• ~4000 well-sampled SNe Ia to z ~1
• Sensitive to geometry
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Sullivan, etal
DES Science Summary
Four Probes of Dark Energy
• Galaxy Clusters
• ~100,000 clusters to z>1
• Synergy with SPT, VHS
• Sensitive to growth of structure and geometry
Forecast Constraints on DE
Equation of State
DES
• Weak Lensing
• Shape measurements of 200 million galaxies
• Sensitive to growth of structure and geometry
• Baryon Acoustic Oscillations
• 300 million galaxies to z = 1 and beyond
• Sensitive to geometry
Planck prior assumed
• Supernovae
• 30 sq deg time-domain survey
• ~4000 well-sampled SNe Ia to z ~1
• Sensitive to geometry
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Factor 3-5 improvement over
Stage II DETF Figure of Merit
DES Science Summary
Four Probes of Dark Energy
• Galaxy Clusters
• ~100,000 clusters to z>1
• Synergy with SPT, VHS
• Sensitive to growth of structure and geometry
Forecast Constraints on DE
Equation of State
DES
• Weak Lensing
• Shape measurements of 300 million galaxies
• Sensitive to growth of structure and geometry
• Baryon Acoustic Oscillations
• 300 million galaxies to z = 1 and beyond
• Sensitive to geometry
Planck prior assumed
• Supernovae
• 30 sq deg time-domain survey
• ~4000 well-sampled SNe Ia to z ~1
• Sensitive to geometry
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Factor 3-5 improvement over
Stage II DETF Figure of Merit
DECam First Light
September 12, 2012
Covered in 258 publications in 36 countries, plus Jay Leno’s monologue
Fornax Cluster
NGC 1365
0.8” images recorded within
first few nights of first light!
Small Magellanic Cloud
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CTIO: great astronomical site with great telescope
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Many People Made this Possible
• Scientists, technicians, and engineers from all
the DES institutions around the globe
• Funding agencies and institutions in the US,
Spain, UK, Brazil, Germany, and Switzerland
• Special thanks to Brenna Flaugher, Alistair Walker,
Tim Abbott, Chris Smith, DES collaborators, CTIO
and FNAL technical staff
• Special shout-out to John Peoples, DES Director
2004-2010
The success of this project is the direct result of
hard work by many who cannot be here today:
please thank them when you see them!
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And Happy 50th Birthday CTIO!
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