Transcript Transparencies - Rencontres de Moriond

Precision Studies of Dark Energy with the
Large Synoptic Survey Telescope
David L. Burke
SLAC
for the
LSST Collaboration
Rencontres de Moriond
Contents and Structures of the Universe
The LSST Collaboration
Brookhaven National Laboratory
Harvard-Smithsonian Center for Astrophysics
Johns Hopkins University
Las Cumbres Observatory
Lawrence Livermore National Laboratory
National Optical Astronomy Observatory
Ohio State University
Pennsylvania State University
Research Corporation
Stanford Linear Accelerator Center
Stanford University
University of Arizona
University of California, Davis
University of Illinois
University of Pennsylvania
University of Washington
Outline
• The LSST Mission
• The LSST Telescope and Camera
• Dark Energy Science
• Schedule and Plans
The LSST Mission
Photometric survey of half the sky ( 20,000 square degrees).
Multi-epoch data set with return to each point on the sky
approximately every 3 nights for up to 10 years.
Prompt alerts (within 60 seconds of detection) of transients to
observing community.
Fully open source and data.
Deliverables
Archive 3 billion galaxies with photometric redshifts to z = 3.
Detect 250,000 Type 1a supernovae per year (with photo-z < 1).
LSST Performance Specifications
Cadence of two 15 second exposures with 2 second read-out followed
by 5 second slew (open-loop active optics) to new (nearby) pointing.
FOV = 3.5 degrees diameter.
Single-exposure Depth = 24.5 AB mag. (r-band)
Stacked (300-400 exposures) Depth = 27.8 AB mag. (r-band)
Median Image PSF (FWHM) = 0.7 arc-sec.
Broad-band (ugrizy; 350nm-1050nm) internal photometric accuracy of
0.010 mag (zero-point across the sky).
Relative astrometric accuracy of 10 mas.

Fast, Wide, Deep, and Precise
Telescope and Camera
3.4m Secondary
Meniscus Mirror
3.5° Photometric Camera
8.4m Primary-Tertiary
Monolithic Mirror
Telescope Optics
PSF controlled over full FOV.
Polychromatic diffraction energy collection
Paul-Baker Three-Mirror Optics
8.4 meter primary aperture.
3.5° FOV with f/1.23 beam
and 0.20” plate scale.
Image diameter ( arc-sec )
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
80
160
240
320
Detector position ( mm )
U 80%
G 80%
R 80%
I 80%
Z 80%
Y 80%
U 50%
G 50%
R 50%
I 50%
Z 50%
Y 50%
Similar Optical Mirrors and Systems
Large Binocular Telescope
f/1.1 optics with two 8.4m primary mirrors.
SOAR 4.2m meniscus
primary mirror
Camera
Filters and
Shutter
Cryostat
Focal Plane Array
(at 153 K)
Refractive Optics
Focal Plane Array (FPA)
Pixels: 3.2  109 on 10 mm pitch.
Plate Scale: 0.200 arc-sec.
FPA Flatness: 10 mm peak-valley.
“Raft” of nine
4k4k CCDs
3.5° Field of View
(634 mm diameter)
Shack-Hartmann
Wavefront Sensors and
Fast Guide Sensors
Survey Power
320
280
Etendue (m2 deg2)
240
200
160
120
80
40
0
LSST
PS4
PS1
Subaru CFHT
SDSS
MMT
DES
4m
VST
VISTA SNAP
IR
Opt+IR
Multi-Epoch Data Archive
Average down instrumental
and atmospheric statistical
variations.
Large dataset allows
systematic errors to be
addressed by subdivision.
Multi-Epoch Data Archive
Average down instrumental
and atmospheric statistical
variations.
Large dataset allows
systematic errors to be
addressed by subdivision.
LSST Dark Energy Highlights
o
Weak lensing of galaxies to z = 3.
Two and three-point shear correlations in linear and non-linear
gravitational regimes.
o
Supernovae to z = 1.
Discovery of lensed supernovae and measurement of time
delays.
o
Galaxies and cluster number densities as function of z.
Power spectra on very large scales k ~ 10-3 h Mpc-1.
o
Baryon acoustic oscillations.
Power spectra on scales k ~ 10-1 h Mpc-1.
Disclosure and Agreement
Unless stated otherwise, error forecasts are not marginalized over unspecified parameters.
Generally, flat-space ΛCDM values are assumed for unspecified parameters.
Do you accept the terms and conditions of this agreement?

I accept.
I do not accept.
Weak Lensing Geometry
Sheared Image
a = 4GM/bc2
q
DS
Impact Parameter b
DLS
Shear
DLS
g~q=
4GM/bc2
DS
Cosmology changes
geometric distance factors.
Gravity & Cosmology
change the growth rate of
mass structure.
Shear Power Spectra Tomography
Measure
• Shear spatial auto-correlation binned in z.
• Cross correlations between different bins in z.
Differing sensitivities to
cosmology and gravity.
0.01
0.001
Linear regime
Needed Shear Sensitivity
CDM
Non-linear regime
 LSST expects well below 0.001 in residual shear error ….
Weak Lensing Through the Atmosphere
Data from Prime-Cam on 8-m Subaru
Single 10 sec exposure in 0.65 arcsec seeing.
Raw
De-trailed
<shear>
<shear>
= 0.04
0.07
PSF Corrected
<shear>
= 0.000013
0.000007
LSST Goal: Residual shear  0.0001.
Train on
random half of
the stars;
measure
residual shear
on other half.
Residual 2-Point Shear Correlations
LSST multi-epoch survey provides sensitivity well below target signal.
LCDM shear
signal
Typical separation of reference
stars in LSST exposures.
Photometric Redshifts and
Weak Lensing
Contours of constant error in w and wa as
functions of statistical and systematic
photo-z errors.
Ma, Hu, Huterer (2005)
Need to know bias and
resolution in z with good
accuracy. LSST goal …
 zbias  0.002  (1 + z)

 Z
 0.003  (1 + z)
… will match systematic
errors in cosmological
parameters to statistical
errors for z  3 .
Photo-z Calibration Campaign
Together
with angular
correlations
• Transfer fields - 200,000 galaxies with 12-band
photo-z
redshifts.
of galaxies, this training set
• Calibrate 12-band photo-z with subset of 20,000
redshifts.
enablesspectroscopic
LSST 6-band photo-z
error calibration to better than
required for LSST statistics limit
Simulation of 12-band
Simulation of 6-band
precision cosmology
photo-z calibration field
photo-z distribution for
at 26 AB mag.
LSST dataset.
z  0.05 (1+z)
z  0.03 (1+z)
Need to calibrate transfer photo-z to 10%
accuracy to reach desired precision
Studies of Supernovae with LSST
LSST Supernovae Data Sets
Survey cadence will detect 250,000
supernovae per year (to z  0.8), and
provide photometry every three days in
rotating colors (primarily r, i, and z).
Simulated light curves from the
LSST deep field survey.
z = 0.8
Nightly deep-field survey will detect and
follow supernovae to z  1.2.
Simulated Hubble diagram from
30,000 supernovae detected over
three years of observing in the LSST
deep-field survey.
photo-z
Weak Lensing and SNe-Ia Forecasts
JDEM
SNe
wa
LSST
WL
Combined
w
Combination of distance
measurements from SNe with
parameters from weak lensing
….
Complementary probes of
cosmology and gravity.
Principal component analysis [Huterer and
Starkman (2003)] of expected sensitivity to
dark energy equation of state.
Baryon Acoustic Oscillations (BAO)
CMB
BAO
RS~140 Mpc
Standard Ruler
Two Dimensions on the Sky
Angular Diameter Distances
Three Dimensions in Space-Time
Hubble Parameter
Baryon-DM Gravitational Effects
Mode Coupling
Clustering In-Fall
Velocity Dispersion along Line-of-Sight
BAO Power Spectra
Two-dimensions on the sky.
3 billion galaxies.
Combination yields accuracy <
~ 2 % on w0.
Three-Dimensional BAO and Hubble
Suppression of line-of-sight modes by photo-z errors.
Pphoto-z(k,μ) = Pz(k,μ) 

exp  c 2 k32 z2 / H 2

Present error on H.
Accuracy needed for LSST WL and SNe.
May do better. We will see.
LSST Project Milestones
and Schedule
2006
Site Selection
Construction Proposals (NSF and DOE).
2007-2008
Complete Engineering and Design
Long-Lead Procurements
2009-2012
Construction and First Light
2013
Commissioning
LSST Site Selection – Two Proposals
Final Selection – 14 April 2006
San Pedro Mártir
Cerro Pachón
Summary
• The LSST will be a significant step in survey capability.
Optical throughput ~ 100 times that of any existing facility.
• The LSST is designed to control systematic errors.
We know how to make precise observations from the ground.
We know how to accurately calibrate photo-z measurements.
Multi-epoch with rapid return to each field on the sky – advantages
likely not yet fully appreciated.
• The LSST will enable multiple simultaneous studies of dark energy.
Complementary measurements to address degeneracy and
theoretical uncertainty in a single survey.
• The LSST technology is ready.