Dark Energy Survey DES Collaboration

8/6/2019 Dark Energy Survey DES Collaboration

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9th UCLA Symposium on Sources and Detection ofDark Matter and Dark Energy in the Universe

John Peoples forthe DES CollaborationFebruary 24, 2010


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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 ofPortsmouth, University of Sussex, University of Nottingham

The University of Pennsylvania

Brazil-DES Consortium

The Ohio State University Argonne National Laboratory

South Bay Consortium: University of California at Santa Cruz, SLAC, Stanford

13 participating institutions and >100 participants


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The DES Approach toProbe Dark Energy

DES will probe Dark Energy by measuring the expansion history ofthe Universe through (i) the redshift dependence of the luminosity distance, angular

diameter distance, and volume element and

(ii) the growth rate of structure

DES will use four techniques, each of which will provide a good testof the nature of the dark energy. Three will measure the spatial distribution of 300 M galaxies in

five bands to ~24th magnitude over the main DES Survey Area. The fourth technique will exploit the nearly standard luminosities

of the type 1a SNe that will be found in the DES SN Survey. They are complementary and will provide insight into systematic

errors through their complementarity.


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I Galaxy Cluster Survey

DES will measure the spatial density of galaxy clustersover an area of 5000 deg2 and make estimates of theirmasses. The number count of galaxies per unit volumeand mass is sensitive to dark energy through its effect on

the angular-diameter distance versus redshift relation andthe growth of structure.

DES will use three methods for cluster selection and

mass estimation: Optical galaxy concentration Sunyaev-Zeldovich effect (SZE) with SPT data Weak Lensing of galaxies behind each selected cluster


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II The Weak Lensing Survey

Strong lensing is apparent in the dramatic distortion of theshapes of individual galaxies behind Abell 2218 causedby the strong gravitational field of the cluster.

Weak lensing is much more subtle.


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II Weak Lensing

Weak lensing is the small distortion of individual galaxy images dueto the bending of light as it passes by galaxies and clusters ofgalaxies. It can be measured statistically. The correlations of thegravity induced distortions of the galaxy shapes are sensitive to dark

energy through its effect on the angular diameter distance versusredshift relation and on the growth of structure.

Measurements of weak lensing are sensitive to the systematicdistortions of the optical system point spread function. The techniquerequires excellent control of the systematic errors that contribute to

the observed shapes of the galaxies. DES is placing great emphasison understanding and controlling both hardware and softwarecontributions to these errors.


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III Large Scale Structure fromthe Galaxy Survey

Baryon Acoustic Oscillations are imprinted on the large-scalestructure of the spatial distribution of the 300 M galaxies in the DESvolume. They are sensitive to dark energy through its effect on theangular-diameter distance versus redshift.

SDSS Data (Eisenstein et al)


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IV The Supernovae Survey

The luminosity distance measurement oftype 1a SNe as a function of redshift isdirectly affected by dark energy and iscurrently the most proven technique.

The DES SN Survey will produce ~2000well-measured SNe Ia light curves in therange 0.3 < z < ~1. This will allow a moreextensive exploration of systematic errorsthan will be possible before DES.

Improved photometric precision via in-situ photometric responsemeasurements.

SDSS


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Photometric Redshifts

Measure relative flux in

grizY filters and track the

4000 A break

Estimate individual galaxy

redshifts to an accuracy of(z) < 0.1 (~0.02 for clusters)

Sufficient precision for

Dark Energy probes, provided

error distributions are well

measured.

Good detector response in

zband filter needed to reach z~1.5

Elliptical galaxy spectrum


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DESgriz filters10 Limiting Magnitudes

g 24.6r 24.1

i 24.0

z 23.9

+2% photometric calibration

error added in quadrature

Key: Photo-z systematic errors

under control using existing

spectroscopic training sets to

DES photometric depth

Galaxy Photo-z Simulations

+VISTA VHS+ J, K, H

DES

Cunha, etal

DES + VHS on

ESO VISTA 4-m

enhances science reach


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Elements of the Dark Energy Survey

3 deg2 CCD camera (DECam)

Data Management System(DES DM)

Improvements to the CTIO-Blanco infrastructure (CFIP)

Two multiband surveys:

- Main Survey: 5000 deg2

- SNe 1a survey: 5 fields (3 deg2

)- Filters: g, r, i, z, Y, from DESand

J, H & K from VHS- Duration 2011-2016 (525 nights)

Blanco 4-meter at CTIO


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THE DECAM PRIME FOCUS CAGE

Replaces the existing prime focus cage on the Blanco13


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The Blanco Telescope

Commissioned in 1974 primary mirrorquality (D80 = 0.25 arcsec) definedstate-of-the-art.

The new Telescope Control System willbe complete in August 2010

CTIO is building a clean room and willprovide cryogens for cooling DECam.

CTIO has repaired the primary mirrorsupports thereby eliminating anastigmatism problem.

Site Seeing:-Mean site seeing at 5m above ground = 0.65arcsec

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Blanco Primary Mirror

High-quality primary, D80 atmanufacture: 0.25

Radial supports rebuild has

fixed the astigmatism problem Active Optics

33-pad system, LUT driven,updated every few months

DECam will provide in-lineupdates (via donut); closed

loop during observationspossible

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CCD Layout on the Focal Plane

On the Focal plane

62: 2k x 4k science

CCDs

4: 2k x 2k guide CCDs

Off the Focal Plane

8: 2k x 2k focus and

alignment CCDs

Required Spare CCDs 10: 2k x 4k science

4: 2k x 2k

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DES CCDs

LBNL Design: fully depleted 2kx4k CCDs QE> 50% at 1000 nm, 250 microns thick

15 m pixels, 0.27/pixel

readout 250 kpix/sec, readout time ~17sec

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25

50

75

100

300 400 500 600 700 800 900 1,000 1,100

DECam / Mosaic II QE comparison

Wavelength (nm)

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

LBNL CCDs are 5 timesmore efficient than the Mosaic IICCDs at 1000 nm

DES will spend 46% of surveytime in z band to reach

redshifts of ~1.3

LBNL procures CCD wafers from DALSA, thins, finishes and dicesthe wafers. CCDs are sent to Fermilab for packaging

z band

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CCD packages

Fermilab builds and tests the CCDpackages, each of which includes an indewar cable, JFET and preamp.

Package production line has fabricatedand tested ~ 200 packages.

75 2k x 4k science packages have beentested and qualified. 72 required.

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Imager Vessel and Cart

Imager vessel will be complete in

April 2010

Install engineering grade CCDs in

the Imager in May 2010

Install Imager in in TelescopeSimulator in June 2010

Major systems test of DECam with

the Telescope Simulator from July

to November 2010

Install science grade CCDs in the

Imager in December and performacceptance tests through Q1 2011

Deliver to CTIO in April 2011

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Barrel Corrector and Imager

Lenses are being polished by SESO, cells are being fabricated byUCL and the barrel is being designed and built by Fermilab. Cellsare in fabrication. Complete Corrector in March 2011 and deliver toCTIO in April 2011.


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DECam Optical Blanks at Corningin Jan. 2008

C2

Polishing is in progress at SESO,will finish in June 2010.

C1

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Filter Changer Test Setup atMichigan

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This grid-based, modular data management system wasdeployed and tested in annual Data Challenges (DC) 1-5. DC-5

will be distributed to Science teams on March 1. DC-6a, DC6b


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Telescope Simulator and

Prime Focus Cage Tests

Mechanical fittingand performance

CryogenicPerformance

CCD systemperformance

SISPI (DAQ)performance

DECam systemperformance w/o

optics. Some acceptance

tests at FNAL

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Telescope Simulator underConstruction in Lab A

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Schedule for Completionof the DECam System

Start DECam integration and acceptance tests on theTelescope Simulator: April 2010

Deliver DECam subsystems to CTIO: January to May 2011 Complete integration and acceptance tests at CTIO: Q2 2011 Complete DC-7 with DESDM hardware August 2011 Deliver Community Pipeline to NOAO Q1 2011 Install DECam on the Blanco: Q3 2011 Commission DECam on Blanco on the night sky: Q4 2011

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DES Outlook

By measuring Dark Energy with four, complementarytechniques, DES will advance these techniques and exploretheir systematic error floors.

The Science Working Groups are active. The survey strategy

will deliver substantial science after 2 years. DES is in a unique position to complement the observing

programs of SPT and VISTA Hemisphere Survey (VHS).

DES Data will be available to the community. The DECamSystem will be scheduled for community observations by

NOAO. The 525 nights of scheduled DECam operations should begin

in the fourth quarter of 2011 soon after commissioning iscomplete.


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DES at CTIO


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The Deliverables

From the Collaboration to NOAO1) The DECam instrument itself, a facility-class wide-field optical imager tobe installed at the prime focus of the CTIO Blanco 4m telescope andintegrated into both the telescope system and the standard operation ofCTIO instrumentation, allowing for efficient community use.

2) A data processing pipeline, the Community Pipeline, which will removethe instrumental signatures and provide astrometric and rough photometriccalibration for images taken under a broad, but well defined, set ofobserving modes. This pipeline will be integrated into E2E, the NOAO datamanagement system, and it will comply with appropriate interfaces in thatsystem, and be operational as part of that system.

From NOAO to the Collaboration

3) The Parties agree that the DES Science Program goals can be achievedwith up to 525 scheduled nights with the typical weather conditions that arelikely to be encountered at CTIO over a five year period. NOAO will makethis time available to the Collaboration.


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Forecast Constraints

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 havent made use of all the information.Further detail of these forecasts is contained in the Dark Energy SurveyScience Program (DES-d0c # 1204).

DETF FoM


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Blanco Performance

Primary mirror repositioned 2.3mm in z-direction

Primary mirror is now centered in cell Coma was dominant and variable, is now the third most

significant aberration and stable.

0

50

100

150

200

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

Frequency

arcsec

Image Quality obtained by theSuperMacho program, 2005B,airmass corrected, VR filter.

Dates: 2005-09-05 to 2005-12-31,Blue: pre-shutdown, red: post-shutdown, approx equal number(~580) exposures each.

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CCD Requirements

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Survey Image System - Process Integration

(Mountaintop Software)

Mostly written in Python (some C code) Shared variables used forcommunication betweensubsystems Python implementation of

German's SML software ICS is Labview withCompact-Rio controllerPrototypes beingused at Fermilab inMCCDTV readout

Some testing atCTIO in June 09


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2k x 4k CCD Production

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Dark Energy Survey DES Collaboration

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