Dark Energy Survey

www.darkenergysurvey.org Dark Energy Survey

Bob Nichol

Based on talk from Josh Frieman The Dark Energy Survey Blanco 4-meter at CTIO • Survey project using 4 complementary techniques: I. Cluster Counts II. Weak Lensing III. Large-scale Structure IV. Supernovae • Two multiband surveys: 5000 deg2 grizY to 24th mag 30 deg2 repeat (SNe) • Build new 3 deg2 FOV camera and Data management system Survey 2012-2017 (525 nights) Facility instrument for Blanco

The DES Collaboration Fermilab University of Illinois at Urbana-Champaign/NCSA University of Chicago Over 120 members Lawrence Berkeley National Lab plus students & NOAO/CTIO postdocs DES Spain Consortium DES United Kingdom Consortium Funding: DOE, NSF; University of Michigan UK: STFC, SRIF; Ohio State University Spain Ministry of University of Pennsylvania Science, Brazil: DES Brazil Consortium FINEP, Ministry of Argonne National Laboratory Science, FAPERJ; SLAC-Stanford-Santa Cruz Consortium Germany: Excellence Universitats-Sternwarte Munchen Cluster; collaborating Texas A&M University institutions plus Associate members at: Brookhaven National Lab, U. North Dakota, Paris, Taiwan

3 Project Structure & Timeline • 3 Construction Projects: • DECam (hosted by FNAL; DOE supported) • Data Management System (NCSA; NSF support) • CTIO Facilities Improvement Project (NSF/NOAO) • NOAO Blanco Announcement of Opportunity 2003 • DECam R&D 2004-8 • Camera construction 2008-11 • Final testing, integration now on-going • Shipping components to Chile this year • Installation on telescope begins early 2012 • First light DECam on telescope mid-2012 • Commissioning and Science Verification: summer/Fall 2012 • Survey operations begin: Fall 2012

4 Dark Energy Camera

Mechanical Interface of CCD DECam Project to the Blanco Readout

Optical Hexapod: Filters & Corrector optical Shutter Lenses alignment

5 DECam CCDs

• 62 2kx4k fully depleted CCDs: 520 Megapixels, 250 micron thick, 15 micron (0.27”) pixel size • 12 2kx2k guide and focus chips • Excellent red sensitivity Developed by LBNL • Roughly twice the number of science-grade CCDs packaged DECam / Mosaic II QE comparison and tested 100

60 50 QE, LBNL (%) 40 QE, SITe (%)

0 300 400 500 600 700 800 900 1000 1100 Wavelength (nm)

6 DECam CCDs

• 62 2kx4k fully depleted CCDs: 520 Megapixels, 250 micron thick, 15 micron (0.27”) pixel size • 12 2kx2k guide and focus chips • Excellent red sensitivity • Roughly twice the number of g r i z Y science-grade CCDs packaged DECam / Mosaic II QE comparison and tested 100

60 50 QE, LBNL (%) 40 QE, SITe (%)

0 300 400 500 600 700 800 900 1000 1100 Wavelength (nm)

7 Asahi filters Optics

• Field of view: 2.2o diameter Attachment ring • Good image quality across FOV Bipods • Optical elements being aligned in Focal plane barrel at UCL, will ship to CTIO Nov. C5, vacuum window C4

Filters & Shutter

C2 - C3

S. Kent (FNAL) C1

8 • DECam mounted on Telescope Simulator at Fermilab in early 2011

9 DES: Recent Progress

• 4 of 5 filters (rizY) delivered to CTIO despite earthquake, tsunami • Prime focus cage, hexapod, filter changer, shutter, cooling system components all safely arrived on the mountain, tested, and many components installed, including extensive work on cooling system. DAQ computers, RASICAM (cloud cam), new flat screen installed. • DECam imager with full complement of science-grade CCDs completed, will ship to Chile Nov. • Lenses aligned in their cells. Cells being aligned in barrel (UCL). Ship to Chile Dec. • CTIO glycol system overhauled, clean room nearly ready for DECam • Data Management secured major NSF grant for operations; major progress on astronomy codes, processing capability, database; release of latest Data Challenge simulation outputs to DES collaboration last week.

10 DECam

C4 in its cell (UCL)

New flat-field Screen (CTIO)

Completed Imager (FNAL)

11 Blanco Telescope Upgrades

• CTIO Facilities Improvement Project – – Primary mirror radial supports redesigned & swapped out – Telescope Control System being upgraded – Telescope Environmental Control System improved – Various other Facility Improvements completed or underway: • Clean Room built inside the Blanco Coudé Room • Upgrades to the building glycol system • Relocated and enlarged Control Room & Computer Room • Installation of utility & cryogen lines for DECam and NEWFIRM • Enhanced bandwidth from La Serena to the USA • Data Transport System for reliable data transfer DES Observing Strategy

• Sept-Feb observing seasons Survey Area 5000 sq deg • 80-100 sec exposures • 2 filters per pointing • gr in dark time Overlap with SDSS equatorial • izy in bright/grey time Stripe 82 for calibration (200 sq deg) • Photometric calibration: overlap tilings, standard stars, spectrophotometric calibration system, preCAM • 2 survey tilings/filter/year 2 tilings 3 tilings • Interleave 10 SN fields in griz if non-photometric or bad seeing or time gap (aim for ~5 day cadence) • Overlap SPT, VISTA surveys 13

DES Calibration Plan

1. Instrumental Calibration (Nightly & Periodic): Create biases, dome flats, linearity curves, cross-talk coefficients, system response maps. 2. Photometric Monitoring: Monitor sky with new 10µm All-Sky Cloud Camera. 3. Nightly and Intermediate Calibrations: Observe standard star fields with DECam during evening and morning twilight and at least once in the middle of the night; fit photometric equation; apply the results to the data. 4. Global Relative Calibrations: Use the extensive overlaps between exposures over multiple tilings to tie together the DES photometry onto an internally consistent system across the entire DES footprint. 5. Global Absolute Calibrations: Use DECam observations of spectrophotometric standards in combination with periodic measurements of the full DECam system response map to tie the DES photometry onto an AB magnitude system. 6. PreCam Survey: Use grizy standards from PreCam Survey for nightly calibrations and calibrated PreCam fields to improve the DES Global Relative Calibrations. 14 DES Science Summary

Four Probes of Dark Energy Current Constraints on DE • Galaxy Clusters Equation of State • ~100,000 clusters to z>1 • Synergy with SPT, VHS • Sensitive to growth of structure and geometry • Weak Lensing • Shape measurements of 300 million galaxies • Sensitive to growth of structure and geometry • Large-scale Structure • 300 million galaxies to z = 1 and beyond • Sensitive to geometry • Supernovae • 30 sq deg time-domain survey • ~4000 well-sampled SNe Ia to z ~1 • Sensitive to geometry Sullivan, etal 15 DES Science Summary Forecast Constraints on DE Four Probes of Dark Energy Equation of State

• Galaxy Clusters DES • ~100,000 clusters to z>1 • Synergy with SPT, VHS • Sensitive to growth of structure and geometry • Weak Lensing • Shape measurements of 300 million galaxies • Sensitive to growth of structure and geometry • Large-scale Structure • 300 million galaxies to z = 1 and beyond Planck prior assumed • Sensitive to geometry • Supernovae • 30 sq deg time-domain survey • ~4000 well-sampled SNe Ia to z ~1 Factor 3-5 improvement over • Sensitive to geometry Stage II DETF Figure of Merit 16 DES Science Summary Forecast Constraints on DE Four Probes of Dark Energy Equation of State

• Governing documents for the collaboration: – MOU between Fermilab, NCSA, NOAO: construction & operations – Membership Policy: DES institutions & people – Publication Policy: authorship, procedures for internal vetting of papers before submission – Science Committee Charter: sets up Science Working Groups to organize/coordinate science analyses, including Supernova Working Group

http://www.darkenergysurvey.org/reports

18 DES Management Structure Science Committee comprises co-coordinators of Science Working Groups Collaboration with Community

• External Collaborators (Membership Policy): • Scientists from non-DES institutions who can provide DES with either special expertise or access to resources not otherwise available to the collaboration • Access to DES data for focused project or broader set of projects. Broader scope in exchange for more substantial technical contributions to DES. • Sponsored by & collaborate with DES scientists, abiding by DES Publication Policy • EC proposals vetted by Working GroupsàMembership Committeeàapproved by Management Committee

21 Conclusion

• DES poised to take the next step in understanding the nature of dark energy, with survey operations starting next year. • DES data processed through DES Data Management system will be available to the public 12 months after it’s taken (raw and processed images), with periodic releases of co-added images and catalogs. Immediate release of transients. • DECam, with its associated Community Pipeline, will be a powerful imaging instrument for community use. • There are opportunities for synergistic observations with community participation (e.g., extension of time domain observations throughout the year).