Large Synoptic Survey Telescope

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Large Synoptic Survey Telescope

• EDEN Workshop on Dark Energy
• 7-9 December 2005
• Kirk Gilmore
• Stanford/SLAC/KIPAC
• for the LSST Collaboration

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LSST Concept
Design Telescope and Camera as a Single
Instrument

• 8.4 Meter Primary Aperture
• 3.4 M Secondary
• 5.0 M Tertiary
• 3.5 degree Field Of View
• 3.2 Gigapixel Camera
• 4k x 4k CCD Baseline
• 200 detectors
• 65 cm Diameter
• Six Filters
• 30 Second Cadence
• Highly Dynamic Structure
• Highly Parallel Readout
• Accumulated depth 27 mag. in each filter over
  10y
• Data Storage and Pipelines 18Tb/night!
• Etendue 270

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LSST Management Structure
Board of Directors
President John Schaefer
14 Institutions 95 people
Director Anthony Tyson Steve Kahn, Deputy
Project Manager Donald Sweeney Victor Krabbendam,
Deputy
Science Advisory Committee (SAC) Michael Strauss
System Engineering William Althouse
System Scientist Chair of Science
Council Zeljko Ivezic
Ed Pub Outreach Suzanne Jacoby
Simulation Data Phil Pinto
System Calibration David Burke
Camera Steven Kahn, Sci. Kirk Gilmore, Mgr.
Telescope/Site Charles Claver, Sci. Victor
Krabbendam, Mgr.
Data Management Timothy Axelrod, Sci. Jeffrey
Kantor, Mgr.
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Principle LSST Science Missions

• Dark Energy / Matter
• Weak lensing - PSF Shape/ Depth / Area
• Super Novae Photo z Filters /
• Map of Solar System Bodies
• NEA Cadence
• KBO -
• Optical Transients and Time Domain
• GRB Afterglows Image Differencing
• Unknown transients -
• Assembly of the Galaxy and Solar Neighborhood
• Galactic Halo Structure and Streams from proper
  motions

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Massively Parallel Astrophysics

• Dark matter/dark energy via weak lensing
• Dark matter/dark energy via supernovae
• Dark Energy via Baryon Acoustic Oscillations
• Galactic Structure encompassing local group
• Dense astrometry over 20000 sq.deg rare moving
  objects
• Gamma Ray Bursts and transients to high redshift
• Gravitational micro-lensing
• Strong galaxy cluster lensing physics of dark
  matter
• Multi-image lensed SN time delays separate test
  of cosmology
• Variable stars/galaxies black hole accretion
• QSO time delays vs z independent test of dark
  energy
• Optical bursters to 25 mag the unknown
• 5-band 27 mag photometric survey
• Solar System Probes Earth-crossing asteroids,
  Comets
• Extragalactic stars

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LSST probes of dark energy

• WL shear-shear tomography
• WL bi-spectrum tomography
• Distribution of 250,000 shear peaks
• Baryon acoustic oscillations
• 2.5 million SNe Ia, zlt0.8
• 60,000 SNe Ia, zlt1.2
• Low l, 2p sky coverage
• 3x109 galaxy sources
• probe g(z) and d(Z) separately
• multiply lensed AGNs and SNe

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Why is the LSST unique?
Primary mirror diameter
Field of view (full moon is 0.5 degrees)
0.2 degrees
10 m
3.5 degrees
Keck Telescope
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LSST Reference Optical Design
6.39m
3.42m CA OD
8.36m CA OD
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Sample Simulator Run Output
Weak Lensing w/SRD visit requirements NEA
w/Ivezic-Harris cadence SuperNova w/ 5 band
colors, primary light curve in r 188,447
visits 649 WL fields 48 SN field-seqs 1858 NEA
field-seqs
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Science Simulator Overview
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LSST Filter Bandpass Definitions

• SDSS
• Band-pass Transition
• Half Maximum Transmission Wavelength
  (nm)
• g r i z
  
• Blue side 402 552 693 840
• Red side 548 693 851 -
• Successful because it has demonstrated
• Photometric redshifts of galaxies
• Separation of stellar populations
• Photometric selection of quasars

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LSST Filter Bandpass Definitions
SDSS Band-pass Transition Half Maximum
Transmission Wavelength (nm)
g r i z Blue side
402 552 693 840 Red side 548 693
851 - LSST Band-pass Transition Half
Maximum Transmission Wavelength (nm)
u g r i z
Y Blue side 350 400 552 691 818 948
Red side 400 552 691 818 922
1060
G-Balmer break _at_400 R-matches SDSS I-red
side short of sky emission _at_826 Z-red
side stop before H2O bands Y-Red cutoff
before detector cutoff
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G-Band
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LSST filter set

• System optical throughput analysis
• Meets filter complement, performance
  requirements
• Meets image depth, image quality requirements
  

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Number of Filters
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Filter Set Simulations Summary
Filter Depth (in 20s) u 22.5 g
24.3 r 24.2 I 23.4 z
22.4 Y 21.5
Input SEDs valid for zlt1 photoz relation for
I-band single pass lt 23.4 200 passes lt
25.0 400 passes lt 26.65 all S/N10

• Some basic conclusions
• u-band reduces the scatter for z lt 0.5 sources
• y-band keeps the scatter tight to z1.6

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Science Requirements Document

• http//www.lsst.org
• Baseline Configuration

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LSST and Dark Energy

• LSST will measure 250,000 resolved high-redshift
  galaxies per square degree! The full survey will
  cover 18,000 square degrees.
• Each galaxy will be moved on the sky and slightly
  distorted due to lensing by intervening dark
  matter. Using photometric redshifts, we can
  determine the shear as a function of z.

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The Lensing Pipeline

• Object detection, star-galaxy classification
• PSF measurement from stars
• PSF interpolation onto galaxy positions
• Galaxy shape measurement and PSF deconvolution
• Shear correlation measurement Photo-z binning
  Lensing tomography ? cosmological parameters
• Systematic errors enter at all stages. Steps 3
  and 4 are critical
• PSF interpolation and deconvolution, as errors in
  these lead to
• systematic errors in the shear correlations.
• For a detailed disscussion see Jain, Jarvis,
  Bernstein 2005, astro-ph/0510231

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Error Forecasts for w0 and wa
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Baryon Acoustic Oscillations A Standard Ruler
Constraints on
Hubble Parameter
Hu Zhan UC Davis 2005
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Need for High-z Data Curvature

• CMB priors flatness
• 4 low-z bins (0.2 z 1.4)

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Science Objectives Drive System
Requirements

• Image Quality
• f/1.25 beam
• Large focal Plane
• Construction
• Techniques

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Telescope Development
LSSTs Ohara E-6 Glass
Facility and Dome Definition
M2
Camera interface
LBTs are Done GMT In Casting, LSST Cast Nov 05
Structural Analysis Mode 1 10.0 Hz
M1/M3 Evaluation
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Optical design
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Camera Development
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Focal plane array
3.5 FOV ? 64 cm dia
Strawman CCD layout 4K x 4K, 10 µm pixels 32
output ports
201 CCDs total
Raft 9 CCDs 1cm x 1cm reservedfor wavefront
sensors
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LSST Final Three Sites
San Pedro Martir
Cerro Pachon
Las Campanas
Site Evaluation
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LSST Data to Public The New Sky

• LSST Transforms the Sky
  to Disk Farms
• Entire static co-adds 20,000 sq.deg 6-band 21TB
  FITS.gz
• Lower res color JPG 177GB (0.4 arcsec res)
• Download in 30 min on 1Gb link
  3 billion galaxies
• Overlay graphics xray, radio, mass, other
• Dynamic sky
• Alerts, overlay animation graphics, orbits,
  postage stamp images
• LSST_at_Home many small images downloaded,
• gt10k ops
  per pixel for load balance
• Celestial cinematography movies of
  patches of sky
• Photometric catalog 10 TB

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LSST System extends beyond LSST

• Worldwide follow-up
• OIR photometry, spectroscopy of selected
  objects
• Deep spectroscopic calibration of photo-z
• Drill down in selected areas
• Spitzer IR HST 10-band deep photo-z
• VLT Keck Subaru spectroscopy (WFMOS)
• Understand sample selections

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Project Baseline Schedule Plans
NSF D D Phase
MREFC Construction Phase
CommScience
First Light
Submit MREFC
Mirror Fabrication/ Cell Assembly
Telescope
Site Preparation
Mount/Dome
System Integration
Camera fabrication integration
Camera Design
Camera
Sensor Devl and protoype
Sensor Fabrication
Software Preliminary Design
Software Final Design
Data Mngt
SoftwareValidation
Software Integration
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