Dark Energy Survey Motivation

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Dark Energy SurveyMotivation
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 no understanding
1998 and 2003 Science breakthroughs of the year
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Probes of Dark EnergyMap the cosmological
density field

• The rate of growth of structure is determined by
  the amount and distribution of dark matter, dark
  energy and by the expansion rate of the universe

zgt30
z0
Count the Galaxy Clusters as a function red
shift and cluster mass Measure the spatial
clustering of galaxies as a function of red shift
(angular power spectrum) Measure the distortion
in the apparent shape of galaxies due to
intervening galaxy clusters and associated clumps
of dark matter (weak lensing) Use supernovae as
standard candles to measure the expansion rate
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Cluster of Galaxies Largest gravitationally
bound objects Size 1025 cm Megaparsec (Mpc)
Mass 1015 Msun
What is the cluster redshift? What is the
cluster mass?
not completely different from jet clustering in
collider physics but also have depth (red shift)
info.
SDSS data
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The Dark Energy Survey (DES)

• Proposal
• Perform a 5000 sq. deg. survey of the southern
  galactic cap
• Measure dark energy with 4 complementary
  techniques
• New Instrument (DECam)
• Replace the PF cage with a new 2.2 FOV, 520 Mega
  pixel CCD camera optics
• Time scales
• Inst. Construction 2008-2011
• Survey 525 nights during Oct.Feb. 2011-2016
• Funding
• DOE, NSF, STFC (UK), Ministry of Education and
  Science (Spain), FINEP (Brazil), and the 11
  Collaborating Institutions

Use the Blanco 4M Telescope at the
Cerro-Tololo Inter-American Observatory (CTIO)
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The DES Instrument DECam

• To meet the DES science requirements, within the
  allocated time period DECam must have
• 3 sq. deg. field of view ( 0.5 meter diameter
  focal plane)
• excellent optical image quality
• red sensitive CCDs (from LBNL)
• g,r,i,Z,Y filters
• low noise electronics (readout with lt 10 e
  noise!)
• cryogenic cooling system

DECam Focal Plane
62 2kx4k Image CCDs 520 MPix 8 2kx2k
Alignment/focus CCDs 4 2kx2k Guide CCDs
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DES Timeline

• 2004 Fermilab and National Optical Astronomy
  Observatory (NOAO) approvals
• April 1st presentation to the FNAL PAC
• July Stage 1 approval by the FNAL director,
• September NOAO approved the DES proposal
• 2005 Nov. DOE approved CD-0 (Mission Need) for a
  ground based DE project
• 2006 P5 and the Dark Energy Task Force
• April DES presentations to P5
• July Dark Energy Task Force report recommended
  projects like DES
• July/Sept. P5 recommendation to proceed with DES.
  Reiterated this in 2008
• 2007 May CD-1 NSF/DOE Review of DES Oct. CD-1
  approval
• 2008 Jan. CD-2/3a NSF/DOE Review of DES
• CD-2 approval for DECam April 29th (Baseline cost
  and schedule)
• CD-3a approval for DECam May 19th (Construction
  start, long lead procurements)
• CD-3b review scheduled for Sept. 2008

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DECam overview

• CCD focal plane is housed in a vacuum vessel (the
  imager) which is supported by the barrel
• LN2 is pumped from the telescope floor to a heat
  exchanger in the imager cools the CCDs to -100 C
• CCD readout electronic crates are mounted to the
  outside of the Imager and are actively cooled
  (UIUC).
• Filter changer (8 filter capacity) and shutter
  form one mechanical unit (UMichigan).
• Hexapod provides focus and lateral alignment
  capability for the corrector-imager system
• Barrel supports the lenses and imager
• DECam weighs about 4 tons (load limit is 6
  tons)

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DECam Project Key People

• Wyatt Merritt is DECam deputy project manager
• Level 2 managers
• CCDs Tom Diehl and Juan Estrada
• Front End Electronics Terri Shaw, Spanish
  coordinator Manel Martinez (Barcelona)
• Optics Peter Doel (University College London)
• Opto-Mechanical Andy Stefanik
• SISPI ( DAQ) Jon Thaler (UIUC) and Klaus
  Honscheid (OSU)
• Survey Planning and Simulations Huan Lin and Jim
  Annis
• Andy and Terri are also the mechanical and
  electrical project engineers, respectively
• STFC has committed funds for polishing of the
  lenses ( 2.5M)
• Spanish funding agencies committed funds for the
  FEE the preproduction boards are already in
  fabrication
• All the universities kicked in cash for early RD
  and the lens blanks

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Current Work at Sidet CCD Packaging and Testing
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Future work at Sidet (Lab A) Telescope Simulator
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Conclusions

• April 2008
• 1 DECam CCD
• with prototype electronics
• in a small test dewar
• on the CTIO 1m (next to the Blanco)

• By April 2011 (lt 3 years from now!) we plan to
  have 62 DECam CCDs in a new camera on the Blanco

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Extras
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Cerro Tololo Inter-American Observatory
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DES Participating Institutions

• Fermilab
• University of Illinois at Urbana-Champaign
• University of Chicago
• Lawrence Berkeley National Laboratory
• University of Michigan
• NOAO/CTIO
• Spain-DES Collaboration
• Institut d'Estudis Espacials de Catalunya
  (IEEC/ICE), Institut de Fisica d'Altes Energies
  (IFAE), CIEMAT-Madrid
• United Kingdom-DES Collaboration
• University College London, University of
  Cambridge, University of Edinburgh, University of
  Portsmouth, University of Sussex
• The University of Pennsylvania
• Brazil-DES Consortium
• The Ohio State University
• Argonne National Laboratory
• 12 participating institutions and gt100
  participants
• DES Funding from DOE, NSF, STFC (UK), Ministry of
  Education and Science (Spain), FINEP (Brazil),
  and the Collaborating Institutions

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Baseline Obligations and Funding Tables for DOE
funds (overhead included, then yr )
Obligations
Funding

• FY07 Funding includes 0.77M of carry-over from
  the RD proposal and funds spent before Aug.1
  (EVMS reporting started)
• FY08 Funding is 5.5M from FNAL, 0.1M from UIUC
  Base Grant

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Blank inspection at Corning
C2
C1
The next step, polishing, will remove only 1
mm per side
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DES Forecasts Power of Multiple Techniques

w(z) w0wa(1a)
Assumptions Clusters ?80.75, zmax1.5, WL
mass calibration BAO lmax300 WL
lmax1000 Statisticalphoto-z systematic errors
only Spatial curvature, galaxy bias
marginalized, Planck CMB prior Factor 4.6
relative to Stage II

DETF Figure of Merit inverse area of ellipse

• geometric
• growth

Stage II not included here
geometric

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Forecast Constraints
DETF FoM

• DESStage II combined Factor 4.6 improvement
  over Stage II combined
• Large uncertainties in systematics remain, but
  FoM is robust to uncertainties in
• any one probe, and we havent made use of all the
  information.
• Further detail of these forecasts is contained
  in the Dark Energy Science Program.

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DES Photometric Redshifts
Elliptical galaxy spectrum

• Measure relative flux in grizY filters and track
  the 4000 A break
• Estimate individual galaxy
• redshifts with accuracy
• ?(z) lt 0.1 (0.02 for clusters)
• Good detector response in
• z band filter needed to reach z1.5