Transcript Slide 1

The Dark Energy Survey (DES)
Sarah Bridle, UCL
On behalf of the DES Collaboration
The Dark Energy Survey
Study Dark Energy using
4 complementary techniques:
Blanco 4-meter at CTIO
I. Cluster Counts
II. Weak Lensing
III. Baryon Acoustic Oscillations
IV. Supernovae
Two multi-band surveys
5000 deg2 g, r, i, z
40 deg2 repeat (SNe)
Build new 3 deg2 camera
and data management system
Survey 2010-2015 (525 nights)
Response to NOAO AO
300,000,000 photometric redshifts
The Dark Energy Survey
Study Dark Energy using
4 complementary techniques:
Blanco 4-meter at CTIO
I. Cluster Counts
II. Weak Lensing
III. Baryon Acoustic Oscillations
IV. Supernovae
Two multi-band surveys
5000 deg2 g, r, i, z
40 deg2 repeat (SNe)
Build new 3 deg2 camera
and data management system
Survey 2010-2015 (525 nights)
Response to NOAO AO
300,000,000 photometric redshifts
The DES Collaboration
Fermilab: J. Annis, H. T. Diehl, S. Dodelson, J. Estrada, B. Flaugher, J. Frieman,
S. Kent, H. Lin, P. Limon, K. W. Merritt, J. Peoples, V. Scarpine, A. Stebbins,
C. Stoughton, D. Tucker, W. Wester
University of Illinois at Urbana-Champaign: C. Beldica, R. Brunner, I. Karliner,
J. Mohr, R. Plante, P. Ricker, M. Selen, J. Thaler
University of Chicago: J. Carlstrom, S. Dodelson, J. Frieman, M. Gladders,
W. Hu, S. Kent, R. Kessler, E. Sheldon, R. Wechsler
Lawrence Berkeley National Lab: N. Roe, C. Bebek, M. Levi, S. Perlmutter
University of Michigan: R. Bernstein, B. Bigelow, M. Campbell, D. Gerdes, A. Evrard,
W. Lorenzon, T. McKay, M. Schubnell, G. Tarle, M. Tecchio
NOAO/CTIO: T. Abbott, C. Miller, C. Smith, N. Suntzeff, A. Walker
CSIC/Institut d'Estudis Espacials de Catalunya (Barcelona): F. Castander, P.
Fosalba, E. Gaztañaga, J. Miralda-Escude
Institut de Fisica d'Altes Energies (Barcelona): E. Fernández, M. Martínez
CIEMAT (Madrid): C. Mana, M. Molla, E. Sanchez, J. Garcia-Bellido
University College London: O. Lahav, D. Brooks, P. Doel, M. Barlow, S. Bridle,
S. Viti, J. Weller
University of Cambridge: G. Efstathiou, R. McMahon, W. Sutherland
University of Edinburgh: J. Peacock
University of Portsmouth: R. Crittenden, R. Nichol, R. Maartnes, W. Percival
University of Sussex: A. Liddle, K. Romer
plus postdocs and students
The Dark Energy Survey UK Consortium
(I) PPARC funding:
O. Lahav (PI), P. Doel, M. Barlow, S. Bridle, S. Viti, J. Weller (UCL),
R. Nichol (Portsmouth), G. Efstathiou, R. McMahon, W. Sutherland (Cambridge)
J. Peacock (Edinburgh)
Submitted a proposal to PPARC requesting £ 1.7M for the DES optical design.
In March 2006, PPARC Council announced that
it “will seek participation in DES”.
PPARC already approved £220K for current R&D.
(II) SRIF3 funding:
R. Nichol, R. Crittenden, R. Maartens, W. Percival (ICG Portsmouth)
K. Romer, A. Liddle (Sussex)
Funding the optical glass blanks for the UCL DES optical work
These scientists will work together through the UK DES Consortium.
Other DES proposals are under consideration by
US and Spanish funding agencies.
The Dark Energy Survey
Camera: DECam
DECam will replace the prime focus cage
4m Blanco telescope
Expected performance of DECAM,
Blanco, and CTIO site
Blanco Effective Aperture/ f number @ prime focus
4 m/ 2.7
Blanco Primary Mirror - 80% encircled energy
0.25 arcsec
Optical Corrector Field of View
2.2 deg.
Corrector Wavelength Sensitivity
<350-1000 nm
Filters
SDSS g, r, i, z (400-1000 nm)
Effective Area of CCD Focal Plane
3.0 sq. deg.
Image CCD pixel format/ total # pixels
2K X 4K/ 520 Mpix
Guide, Focus & Wavefront Sensor CCD pixel format
2K X 2K
Pixel Size
0.27 arcsec/ 15 μm
Readout Speed/Noise requirement
250 kpix/sec/ 10 e
Survey Area
SPT overlap
SDSS stripe 82
Connection region
5,000 sq. deg. total
RA -60 to 105, DEC -30 to -65
RA -75 to -60 , DEC -45 to -65
RA -50 to 50, Dec -1 to 1
RA 20 to 50, Dec -30 to -1
Survey Time/Duration
525/5 (nights/years)
Median Site Seeing Sept. – Feb.
0.65 arcsec
Median Delivered Seeing with Mosaic II on the Blanco
0.9-1.0 arcsec (V band)
Limiting Magnitude: 10 in 1.5” aperture assuming 0.9” seeing
g=24.6, r=24.1, i=24.3, z=23.9
Limiting Magnitude: 5 for point sources assuming 0.9” seeing
g=26.1,r=25.6, i=25.8, z=25.4
DeCam
Optical Lay Out
C1
C2
C3
C4
C5
978mm
Filter
1870mm
i zenith 0
DES and VISTA synergy
DES (griz)
DES+VISTA(JK)
VISTA J (<21) and K (<19) would improve photo-z
by a factor of 2 for z> 1
F. Abdalla, M. Banerji, OL, H. Lin, et al.
DES Forecasts: Power of Multiple
Techniques
Assumptions:
Clusters:
8=0.75, zmax=1.5,
WL mass calibration
w(z) =w0+wa(1–a)
BAO: lmax=300
WL: lmax=1000
(no bispectrum)
Statistical+photo-z
systematic errors only
Spatial curvature, galaxy bias
marginalized,
Planck CMB prior
Factor 4.6 improvement over Stage II
DETF Figure of
Merit: inverse
area of ellipse
68% CL
DES Forecast
Constraints
DETF FoM
•DES+Stage II combined = Factor 4.6 improvement over Stage II combined
•Consistent with DETF range for Stage III DES-like project
•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