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The Dark Energy Survey
DES:Two multi-band surveys:
5000 deg2 g, r, i, z
40 deg2 repeat (SNe)
DIRBE dust map
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
Blanco Telescope
• 4m diameter equatorial mount telescope.
• Located at altitude of 2200m at Cerro Tololo Inter-American
Observatory (CTIO) , Chile (Lat. 30o 10’ S, Long. 70 o 49’ W).
The Dark Energy Survey Camera: DECam
DECam will replace the prime focus cage
4m Blanco telescope
DeCam
Optical Lay Out
C1
C2
C3
C4
C5
978mm
Filter
1870mm
Expected performance of DECAM, Blanco, and
CTIO site
Blanco Primary Mirror - 80% encircled energy
0.25 arcsec
Optical Corrector Field of View
2.2 deg.
Corrector Wavelength Sensitivity
<350-1000 nm
Effective Area of CCD Focal Plane
3.0 sq. deg.
Image CCD pixel format/ total # pixels
2K X 4K/ 520 Mpix
Pixel Size
0.27 arcsec/ 15 μm
Readout Speed/Noise requirement
250 kpix/sec/ 10 e
Median Site Seeing Sept. – Feb.
0.65 arcsec
Median Delivered Seeing with Mosaic II on the
Blanco
0.9 arcsec
Limiting Magnitude: 10 in 1.5” aperture assuming g=24.6, r=24.1, i=24.3, z=23.9,
0.9” seeing
Y=20.5 (VHS J=20.4,
H=20.0, K=19.4)
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
DES Weak Lensing
Current DES WL Work
Science requirements:
• Image quality
• Photometric redshifts
Data management:
• Object selection
• PSF interpolation
• Shear measurement
Theoretical predictions:
• Higher order statistics, small scales
i zenith 0
Photo-z with ANNz
z = 0.13
Collister & Lahav
z input
DES + VISTA (YJHKs)
z output
z output
DES (griz) 5-yr alone
z=0.08
Collister & Lahav
z input
Requirements on photoz scatter from
intrinsic alignments
Bridle & King 2007
== scatter/(1+z)
Current DES WL Work
Science requirements:
• Image quality
• Photometric redshifts
Data management:
• Object selection
• PSF interpolation
• Shear measurement
Theoretical predictions:
• Higher order statistics, small scales
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
Expected galaxy power spectrum
Turnover
Baryon wiggles
Adapted from Wayne Hu’s website
Are wiggles visible in photo-z surveys?
Blake & Bridle 2005
Photo-z error = 0.05 (1+z)
(Realistically large)
Photo-z error = 0.01 (1+z)
(Unrealistically small)
Photo-z with ANNz
z = 0.13
Collister & Lahav
z input
DES + VISTA (YJHKs)
z output
z output
DES (griz) 5-yr alone
z=0.08
Collister & Lahav
z input
Are wiggles visible in photo-z surveys?
Photo-z error = 0.03 (1+z) ~0.06
~ DES griz + VISTA
Yes!
Blake & Bridle 2005
Photo-z error = 0.05 (1+z) ~0.1
~ DES griz
~DES+VISTA
kmax for
linear theory
Chris Blake
DES
~3.5
DES+VISTA
~5
Blake & Bridle 2005
• See also Dolney, Jain & Takada astro-ph/0409445
errors on w from photozs
Priors applied
Results obtained
~DES+VISTA
Chris Blake
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
Supernovae Ia
• Deep imaging in riz of 9 deg2
• 10% of survey time, plus a
larger fraction of nonphotometric time
• Cadence of 5 visits per lunation
• ~1000 well-measured SN Ia
lightcurves, z~1
• Improved photometric precision
via in-situ photometric response
measurements
SDSS
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
Clusters and Dark Energy
~170 000 clusters with >10 bright red-sequence
galaxies, M>~5x1013 Mo to z~1.5
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
DES Forecasts: Power of Multiple Techniques
Assumptions:
Clusters:
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,
8=0.75
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
DES Schedule Goals
• Last week (Jan 2008): Passed US CD2, CD3a approval
• September 2009: DECam maintenance facility operational
• January 2010: New Telescope Controls System operational
on the Blanco
• April 2010: Commission the DES DM at NCSA and transfer
simulated data through the DTS to NCSA.
• April 2010: Deliver a partial SISPI system to CTIO and
begin the integration of SISPI with the telescope controls
system, the DTS, and the DES DM system.
• July 2010: Deliver DECam to CTIO.
• July 2010: Deliver the Optical Corrector to CTIO.
• Complete commissioning and make the first science
observations while the South Galactic Cap is visible
between September 2010 and March 2011.
C1 Slumped
DES Schedule Goals
• Last week (Jan 2008): Passed US CD2, CD3a approval
• September 2009: DECam maintenance facility operational
• January 2010: New Telescope Controls System operational
on the Blanco
• April 2010: Commission the DES DM at NCSA and transfer
simulated data through the DTS to NCSA.
• April 2010: Deliver a partial SISPI system to CTIO and
begin the integration of SISPI with the telescope controls
system, the DTS, and the DES DM system.
• July 2010: Deliver DECam to CTIO.
• July 2010: Deliver the Optical Corrector to CTIO.
• Complete commissioning and make the first science
observations while the South Galactic Cap is visible
between September 2010 and March 2011.
DES Summary
• Weak Lensing
• Baryon Acoustic Oscillations
• Supernovae
• Cluster Counts
→ Build new 3 deg2 camera
– Survey 2010-2015 (525 nights)
– 300,000,000 photometric redshifts
END
Spectroscopic Redshift
Training Sets for DES
Redshift Survey
Overlap with DES
Number of Redshifts
Overlapping DES
Sloan Digital Sky Survey
Southern Equatorial Stripe 70,000, r<20
(Stripe 82)
median z=0.1–0.6
depending on the
sample
2dF Galaxy Redshift Survey
Most of SGP strip and SGP 90,000, bJ<19.45
random fields
median z = 0.1
VIMOS VLT Deep Survey
3 fields at RA/Dec = 2217+00, ~60,000, IAB<24
0226–04, 0332–28
median z ~ 0.8
DEEP2 Redshift Survey
2 fields at RA/Dec = 2330+00, ~30,000, RAB<24.1
0230+00
median z ~ 1