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					                                         Dark Energy Survey
                                             Motivation
                                                           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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Brenna Flaugher FNAL All Experimenters Meeting June 2008
                             Probes of Dark Energy:
                        Map 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
z>30                                                                                 z=0




          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
                                                                                      2
  Brenna Flaugher FNAL All Experimenters Meeting June 2008
            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   3
   Brenna Flaugher FNAL All Experimenters Meeting June 2008
                             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                                     Use the Blanco
• Funding:                                                    4M Telescope
    – DOE, NSF, STFC (UK),                                    at the Cerro-Tololo
      Ministry of Education and                               Inter-American
      Science (Spain), FINEP                                  Observatory (CTIO)
      (Brazil), and the 11
      Collaborating Institutions                                           4
   Brenna Flaugher FNAL All Experimenters Meeting June 2008
                             The DES Instrument: DECam


• To meet the DES science requirements,                           DECam Focal Plane
  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 <
     10 e noise!)                                            62 2kx4k Image CCDs: 520 MPix
   • cryogenic cooling system                                8 2kx2k Alignment/focus CCDs
                                                             4 2kx2k Guide CCDs



                                                                                            5
  Brenna Flaugher FNAL All Experimenters Meeting June 2008
                                         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 29 th (Baseline cost and schedule)
        – CD-3a approval for DECam May 19 th (Construction start, long lead procurements)
        – CD-3b review scheduled for Sept. 2008


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    Brenna Flaugher FNAL All Experimenters Meeting June 2008
                                           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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    Brenna Flaugher FNAL All Experimenters Meeting June 2008
                                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 R&D and the lens blanks
                                                                              8
Brenna Flaugher FNAL All Experimenters Meeting June 2008
               Current Work at Sidet: CCD Packaging
                           and Testing




                                                           9
Brenna Flaugher FNAL All Experimenters Meeting June 2008
                               Future work at Sidet (Lab A):
                                   Telescope Simulator




                                                               10
Brenna Flaugher FNAL All Experimenters Meeting June 2008
                                                    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 (< 3 years from now!) we plan to have 62 DECam CCDs
   in a new camera on the Blanco
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                                                Extras




                                                           12
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            Cerro Tololo Inter-American Observatory




                                                           13
Brenna Flaugher FNAL All Experimenters Meeting June 2008
                           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 >100 participants
DES Funding from DOE, NSF, STFC (UK), Ministry of Education and
  Science (Spain), FINEP (Brazil), and the Collaborating Institutions
                                                                                        14
Brenna Flaugher FNAL All Experimenters Meeting June 2008
                 Baseline Obligations and Funding Tables for
                  DOE funds (overhead included, then yr $)
    Obligations




 Funding




• FY07 Funding includes $0.77M of carry-over from the R&D
  proposal and funds spent before Aug.1 (EVMS reporting started)

• FY08 Funding is $5.5M from FNAL, 0.1M from UIUC Base Grant
                                                                   15
 Brenna Flaugher FNAL All Experimenters Meeting June 2008
                                Blank inspection at Corning




C2




                                                             C1

                                                            The next step, polishing, will remove
                                                            only ~ 1 mm per side                    16
 Brenna Flaugher FNAL All Experimenters Meeting June 2008
             DES Forecasts: Power of Multiple Techniques


w(z) =w0+wa(1–a)

Assumptions:
Clusters:
8=0.75, zmax=1.5,
WL mass calibration
                                                       DETF Figure of
                                                       Merit: inverse
BAO: lmax=300
                                                       area of ellipse
WL: lmax=1000

Statistical+photo-z               geometric+
                                  growth
systematic errors only

Spatial curvature, galaxy
                                  Stage II not
bias marginalized,
                                  included here   geometric
Planck CMB prior

Factor 4.6 relative to Stage II
                                Forecast Constraints

                                                                  DETF FoM




•DES+Stage 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 haven’t made use of all the information.
• Further detail of these forecasts is contained in the Dark Energy Science
Program.                                                                18
Brenna Flaugher FNAL All Experimenters Meeting June 2008
                          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) < 0.1 (~0.02 for clusters)

• Good detector response in
  z band filter needed to reach z~1.5




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