The Large Synoptic Survey Telescopeand Precision Studies of Cosmology

David L. BurkeSLAC

C2CR07Granlibakken, California

February 26, 2007

Brookhaven National Laboratory

California Institute of Technology

Google Corporation

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

Princeton 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

The LSST Collaboration

Outline

• The LSST Mission

• The LSST Telescope and Camera

• Precision Cosmology and Dark Energy

• Schedule and Plans

Concordance and Consternation

Is CDM all there is?

Is the universe really flat?

What is the dark matter? Is it just one thing?

What is driving the acceleration of the universe?

What is inflation?

Can general relativity be reconciled with quantum mechanics?

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 4 nights for up to 10 years.

A new 10 square degree field every 40 seconds.

Prompt alerts (within 60 seconds of detection) to transients.

Deliverables

Archive over 3 billion galaxies with photometric redshifts to z = 3.

Detect 250,000 Type 1a supernovae per year (with photo-z < 0.8).

Telescope and Camera

8.4m Primary-TertiaryMonolithic Mirror

3.5° Photometric Camera

3.4m Secondary Meniscus Mirror

Aperture and Field of View

Primary mirror diameter

Field of view

KeckTelescope

0.2 degrees10 m

3.5 degrees

LSST

Optical Throughput – Eténdue AΩ

0

40

80

120

160

200

240

280

320

Ete

nd

ue

(m

2 de

g2 )

LSST PS4 PS1 Subaru CFHT SDSS MMT DES 4m VST VISTAIR

All facilities assumed operating100% in one survey

Telescope Optics

Polychromatic diffraction energy collection

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 80 160 240 320

Detector position ( mm )

Imag

e di

amet

er (

arc-

sec

)

U 80% G 80% R 80% I 80% Z 80% Y 80%

U 50% G 50% R 50% I 50% Z 50% Y 50%

PSF controlled over full FOV.

Paul-Baker Three-Mirror Optics

8.4 meter primary aperture.

3.5° FOV with f/1.23 beam and 0.20” plate scale.

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 and Focal Plane Array

Filters and Shutter

Focal Plane Array3.2 Giga pixels

~ 2mWavefront Sensors and

Fast Guide Sensors

“Raft” of nine 4kx4k CCDs.

0.65m Diameter

Focal Plane Metrology

Silicon Displacement:CCD Thickness (100m)

+10 m

0 m

-10 m

PSF

Assembly-stage adjustment to achieve tolerance of 10 microns peak-to-valley surface flatness.

Simulated LSST photon beam in silicon.

LSST Site

El Peñón

Cerro Pachón

Gemini South and SOAR

LSST Facility Sketch

LSST Cosmology Highlights

o Weak lensing of galaxies to z = 3. Tomographic shear correlations in linear and

non-linear gravitational regimes.

o Supernovae to z = 1. Lensed supernovae and 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.

More

Propagation of Light Rays

Can be several (or even an infinite number of) geodesics along which light travels from the source to the observer.

Displaced and distorted images.

Multiple images.

Time delays in appearances of images.

Observables are sensitive to cosmic distances and to the structure of energy and matter (near) line-of-sight.

A complete Einstein ring.

Strong Lensing

Galaxy at z =1.7 multiply imaged by a cluster at z = 0.4.

Multiply imaged quasar (with time delays).

Distorted Image

Source

ξi

ξj

Convergence and Shear

“Convergence” and “shear” determine the magnification and shape (ellipticity) of the image.

Distortion matrix

with the co-moving coordinate along the geodesic, and a function of angular diameter distances.

( )

Simulation courtesy of S. Colombi (IAP, France).

Weak Lensing of Distant Galaxies

Sensitive to cosmological distances, large-scale structure of matter, and the nature of gravitation.

Source galaxies are also lenses for more distant galaxies.

Observables and Survey Strategy

Galaxies are not round!

g ~ 30%

The cosmic signal is 1%.

Must average a large number of source galaxies.

Signal is the gradient of , with zero curl.

“B-Mode” must be zero.

Weak Lensing Results

Discovery (2000 – 2003) 1 sq deg/survey 30,000 galaxies/survey

CFHT Legacy Survey (2006) 20 sq deg (“Wide”) 1,600,000 galaxies

“B-Mode”

Requires Dark Energy (w0 < -0.4 at 99.7% C.L.)

Shear Power Spectra Tomography

LSST designed to achieve 0.001 or better residual shear error.

0.01

0.001

Ne

ede

d S

he

ar Se

nsitivity

Linear regime Non-linear regime

CDM

LSST Postage Stamp(10-4 of Full LSST FOV)

Exposure of 20 minutes on 8 m Subaru telescope. Point spread width 0.52 arc-sec (FWHM). Depth r < 26 AB.

Field contains about 10 stars and 100 galaxies useful for analysis.

1 arc-minute

LSST will see each point on the sky in each optical filter this well every 6-12 months.

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.

Residual Shear Correlations

CDM shear signal

Typical separation of reference stars in LSST exposures.

Data from Subaru.

Photometric Measurement of Redshifts “Photo-z’s”

Galaxy Spectral Energy Density (SED)

Moves right larger z.Moves left smaller z.

“Balmer Break”

Photo-z Calibration

Calibrate with 20,000 spectroscopic redshifts.

Need to calibrate bias and width to 10% accuracy to reach desired precision

Simulation of 6-band photo-z.

z 0.05 (1+z)

Simulation photo-z calibration.

z 0.03 (1+z)

Precision on Dark Energy Parameters

Measurements have different systematic limits.

Combination is significantly better than any individual measurement.

Project Schedule

2006 Site SelectionPrimary Mirror Contract (Arizona Mirror Lab)

Construction Proposals (NSF and DOE)

2007-2009 Complete Engineering and DesignLong-Lead Procurements

2010-2013 Construction and First Light

2014 Commissioning and Science

Done