huan lin 1fnal eccmbc workshop 26 may 2006 the dark energy survey (des) huan lin experimental...

Huan Lin1FNAL ECcmbC Workshop 26 May 2006

The Dark Energy Survey (DES)

Huan LinExperimental Astrophysics Group

Fermilab

On behalf of the Dark Energy Survey Collaboration


The Dark Energy Survey (DES)

Study Dark Energy using 4 complementary techniques:

Galaxy clusters Weak lensing Baryon acoustic oscillations Type Ia supernovae

2 Multiband Surveys: 5000 deg2 griz survey of the

Southern Galactic Cap 40 deg2 repeated for supernovae 525 nights (2009-2015) on the CTIO

4m Blanco telescope Build:

Large 3 deg2 mosaic CCD camera and optical corrector for the Blanco

Data management system Response to NOAO AO

Blanco 4m Telescope at the Cerro-TololoInter-American Observatory (CTIO)

Image credit: Roger Smith/NOAO/AURA/NSF

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The DES CollaborationFermilab: 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. WesterUniversity of Illinois at Urbana-Champaign: C. Beldica, R. Brunner, I. Karliner, J. Mohr, R. Plante, P. Ricker, M. Selen, J. ThalerUniversity of Chicago: J. Carlstrom, S. Dodelson, J. Frieman, M. Gladders, W. Hu, S. Kent, R. Kessler, E. Sheldon, R. WechslerLawrence Berkeley National Lab: N. Roe, C. Bebek, M. Levi, S. PerlmutterUniversity of Michigan: R. Bernstein, B. Bigelow, M. Campbell, D. Gerdes, A. Evrard, W. Lorenzon, T. McKay, M. Schubnell, G. Tarle, M. TecchioNOAO/CTIO: T. Abbott, C. Miller, C. Smith, N. Suntzeff, A. WalkerCSIC/Institut d'Estudis Espacials de Catalunya (Barcelona): F. Castander, P. Fosalba, E. Gaztañaga, J. Miralda-EscudeInstitut de Fisica d'Altes Energies (Barcelona): E. Fernández, M. MartínezCIEMAT (Madrid): C. Mana, M. Molla, E. Sanchez, J. Garcia-BellidoUniversity 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, W. PercivalUniversity of Sussex: A. Liddle, K. Romer plus students


Basic Survey Parameters

5000 deg2 Survey Area 4000 deg2 of overlap with South

Pole Telescope (SPT) survey area Also includes SDSS Southern

Equatorial Stripe + deep galaxy redshift survey fields

Limiting Magnitudes Galaxies: 10σ griz = 24.6, 24.1,

24.3, 23.9 Point sources: 5σ griz = 26.1,

25.6, 25.8, 25.4 Observation Strategy

Multiple tilings/overlaps (in units of 100 sec exposures) to optimize photometric calibrations

2 survey tilings/filter/year 1% photometry goal

SPT overlap area

SDSS SouthernEquatorial Stripe

Tie region


The Dark Energy Camera (DECam) 5-element optical corrector

4 filters: g,r,i,z

2k x 4k LBNL CCDs

0.27”/pixel

62 CCD, 520 Megapixel mosaic camera

3 deg2 field of view

3556 mm

1575 mm

Hexapod

Optical Lenses

F8 Mirror

CCDRead out

Filters Shutter


DES CCDs

LBNL CCDs High quantum efficiency in the

red: QE > 50% at 1000 nm 250 m thick, 15 m pixels 17 sec readout time Optimal for z-band observations

needed by DES for galaxies and clusters at redshifts ~ 1 and above

DES CCD wafers First lots have been delivered by

Dalsa and finished by LBNL

First devices are now being packaged, tested, and characterized at Fermilab

DECam / Mosaic II QE comparison

0

10

20

30

40

50

60

70

80

90

100

300 400 500 600 700 800 900 1000 1100

Wavelength (nm)

QE, LBNL (%)QE, SITe (%)

DES CCD QE

Current Mosaic II QE


DES Data Management U. Illinois and NCSA lead the DM project DM System Requirements

Reliably transfer ~300GB/night for 525 nights from CTIO to U. Illinois/National Center for Supercomputing Applications (NCSA)

Automatically process data with built-in quality assurance Archive the data products and serve the processed data to collaboration Provide community access to the archive 1 year after images were collected

DM Team U. Illinois/NCSA, Fermilab and NOAO Additional DES collaborators

Deliverables to DES and astronomical community DM System (High Performance Computing platforms and workstations)

Pipeline middleware Astronomy modules Catalog database Image Archive

Archived science ready DES data


DES Simulations

Yearly cycles of simulations provide data for development of data reduction pipelines and science analysis codes

Completed Level 1 Simulations 500 deg2 galaxy catalog 500 GB of science images; shapelets-based

Ongoing Level 2 Simulations 5000 deg2 galaxy catalog ~5 TB of science images Use collaboration computing resources,

including FermiGrid and Barcelona Marenostrum supercomputer

Recovery of input cosmology from catalogs Future Level 3 Simulations

Suite of full-DES catalogs 1 year of DES imaging data Synergy with DOE SciDAC proposal to

produce large cosmological simulations for dark energy studies

Recovery of input cosmologies from catalogs and images

gri color composite of example Level 1 simulation image

Parent N-body box for Level 2 catalog simulation


DES: Galaxy Clusters Galaxy cluster abundance, mass

function, and correlations sensitive to cosmology via effects on volume and on growth rate of perturbations

Complementary cluster samples DES optical data provide accurate cluster

photometric redshifts South Pole Telescope (SPT) Sunyaev-

Zel’dovich effect (SZE) data provides robust cluster masses

Tens of thousands of clusters in 4000 deg2 area of DES-SPT overlap

Multiple cluster mass estimators (optical richness, SZ, lensing) and cross-checks of sample selection effects

from J. Mohr


Cluster Mass-Observable Calibration

Simulations indicate robust cluster mass vs. SZE flux decrement relationship

Nagai, Motl, et al.

SZE

flu

x

Adiabatic∆ Cooling+Star Formation

small (~10%) scatter

Johnston, Sheldon, et al., in preparation

SDSS DataPreliminaryz<0.3

Lensing will be used to calibrate cluster mass vs. optical richness relationship; cf. SDSS


DES: Weak Lensing

Measure shapes for ~300 million source galaxies

Average galaxy redshift ~0.7 Effective galaxy surface

density of ~10 per arcmin2

Shear-shear and galaxy-shear correlations probe distances and growth rate of perturbations

Also provides independent calibration of cluster masses from D. Huterer

cosmic shear angular power spectrum in 4 redshift bins


DES: Weak Lensing

Red: expected signal

Results from 75 sq. deg. WL Survey with Mosaic II and BTC on the Blanco 4-m (Bernstein et al.)DES: comparable depth: source galaxies well resolved & bright: low-risk

(improved systematic)

(signal)

(old systematic)

• Cerro Tololo Image Quality Sept-Feb

– site median PSF 0.65” FWHM

– Prime Focus (PF) delivered median PSF 0.9” FWHM (used in all DES constraint forecasts)

• DES/CTIO upgrades will stabilize the PSF and should improve the median FWHM:

• DES

– focus and alignment sensors on focal plane: generate focus and lateral alignment information with each image

– active control of camera position: hexapods will provide focus and lateral adjustments of corrector + camera system

– improved thermal environment: heat dissipation will be actively controlled

• CTIO is upgrading the primary mirror radial supports to reduce mirror motions


DES: Baryon Acoustic Oscillations

Angular power spectrum of 300 million galaxies over 5000 deg2

Measured in photo-z bins out to redshifts of 1 and above

Features in the angular power spectrum (e.g. horizon scale at matter-radiation equality, baryon oscillations) provide physically calibrated “standard rods”

Allows measurement of angular diameter distances as a function of redshift to constrain cosmology

SDSS galaxycorrelation function

Acoustic series in P(k) becomes a single peak in (r)

Eisenstein et al.


DES: ISW

8=1.0

8=0.9

w/ photo-z w/o photo-z

from Gaztanaga, Cabre et al.

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DES: Type Ia Supernovae

• Repeat observations of 40 deg2 , using 10% of survey time

• ~1900 well-measured SN Ia lightcurves, 0.25 < z < 0.75

• Larger sample, improved z-band response compared to ESSENCE, SNLS; address issues they raise

• Use a combination of photometric redshifts and spectroscopic redshifts (~25%)

• Develop supernova photo-z and color typing techniques; better host galaxy photo-z’s via stacking of repeat images SDSS


DES Photometric Redshifts

Galaxies: 68% photo-z scatter < 0.1 using optimal neural network or nearest-neighbor polynomial methods

Clusters: robust photo-z’s to redshifts ~1.3, with 68% scatter of 0.02 or less


DES Photometric Redshifts

Normalized photo-z error distribution and best-fit gaussian

Accurate photo-z errors computed using nearest-neighbor error estimator

Large completed and ongoing redshift surveys (SDSS, 2dFGRS, VVDS, DEEP2, …) will provide ~250,000 spectroscopic redshifts to DES depths for accurate photo-z calibrations

Pursuing adding VISTA near-IR data to reduce photo-z errors at z > 1 by factor of 2 to enhance science reach

Actively working to o Optimize photo-z’so Understand photo-z errors o Improve mock galaxy and cluster catalogso Optimize filter bandpasseso Derive photo-z requirements set by

cosmological parameter analyses


Example DES Photo-z Requirements

Weak lensing tomography: want uncertainty in photo-z bias and scatter at the 10-3 level

Supernovae: robust to DES photo-z error, given existing lower-z SDSS spectro-z supernova sample

from D. Hutererfrom Z. Ma

DES Forecasts: Power of Multiple Techniques

Ma, Weller, Huterer, et al.

Assumptions:Clusters: 8=0.75, zmax=1.5,WL mass calibration(no clustering)

BAO: lmax=300WL: lmax=1000(no bispectrum; gal-massincluded in combined)

Statistical+photo-z systematic errors 0.002 only

Spatial curvature, galaxy biasmarginalized

Planck CMB prior

w(z) =w0+wa(1–a) 68% CL

geometric

geometric+growth

Clustersif 8=0.9


Summary DES will measure dark energy using 4 complementary probes

(clusters, weak lensing, BAO, supernovae), using a 5000 deg2 griz survey (to 24th mag) with well-calibrated photometry and photo-z’s

New 3 deg2 DECam mosaic camera provides order of magnitude improvement in survey power over current CTIO Mosaic II camera

The DES plans to start observing in late 2009, assuming DOE project approval

The DES will serve as a valuable legacy data set for cosmology and astrophysics studies for the community

DES is in unique international position to synergize with SPT and VISTA on DETF Stage III time scale; precursor to more ambitious Stage IV projects like LSST and JDEM

huan lin 1fnal eccmbc workshop 26 may 2006 the dark energy survey (des) huan lin experimental...

Documents

wavelength nmdecam mosaic

des data managementu

processed data

data products

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des collaborationfermilab

wavelength nmmosaic

photometry goalhuan