New Directions in Observational
Cosmology: A New View of our Universe
Tony Tyson
UC Davis
Berkeley May 4, 2007
Technology drives the New Sky
 Microelectronics
 Software
 Large Optics Fabrication
Wide+Deep+Fast: Etendue
Primary mirror
diameter
Field of view
(full moon is 0.5 degrees)
0.2 degrees
10 m
Keck
Telescope
3.5 degrees
LSST
Relative Survey Power
320
280
15 sec exposures
2000 exposures per field
2
Etendue (m deg )
240
2
200
160
120
80
40
0
LSST
PS4
PS1
Subaru CFHT
SDSS
MMT
DES
x0.3
4m
VST
VISTA
IR
SNAP
x2
Large Synoptic Survey Telescope
The LSST optical design: three large mirrors
The telescope design is complete
Camera and
Secondary assembly
Finite element
analysis
Carrousel dome
Altitude over azimuth configuration
The LSST site
1.5m photometric
calibration telescope
3.2 gigapixel camera
Raft Tower
L3 Lens
Shutter
L1/L2
Housing
Five Filters in stored location
Camera Housing
L1 Lens
L2 Lens
Filter in light path
Camera body with five filters and shutter
Back Flange
Filter
Changer
rail
Filter
Carousel
Shutter
Manual
Changer
access port
Filter
Changer
The LSST Focal Plane
Wavefront
Sensors (4
locations)
Guide
Sensors (8
locations)
Wavefront Sensor Layout
2d
Focal plane
Sci CCD
40 mm
Curvature Sensor Side View Configuration
3.5 degree Field of
View (634 mm
diameter)
Large CCD mosaics
1E+10
LSST
SNAP (space)
Pan-STARRS
1E+09
CFHT & SAO Megacam
GAIA (space)
Number of pixels
SLAC VXD3
SDSS
1E+08
ESO omegacam
UH4K
lots of 8K mosaics!
1E+07
NOAO4K
1E+06
1990
1992
1994
1996
1998
2000
2002
Year
2004
2006
2008
2010
2012
2014
basic building block: the raft tower
3 x 3 CCD Sensor Array
Raft Assembly
4Kx4K Si CCD Sensor
CCD Carrier
Thermal Strap(s)
SENSOR
Flex Cable &
Thermal Straps
Electronics Cage
Electronics
RAFT TOWER
The LSST thick CCD Sensor
16 segments/CCD
200 CCDs total
3200 Total Outputs
LSST Project
Partnership of government
(NSF and DOE) and private
support.
Milestones and Schedule
Cerro Pachón
2006
Site Selection
Construction Proposals
(NSF and DOE)
2007-2009
Complete Engineering
2010-2015
Construction
2015
Commissioning
The Data Challenge
 ~2 Terabytes per
hour that must be
mined in real time.
 More than 10 billion
objects will be
monitored for
important variations
in real time.
 Knowledge
extraction in real
time.
The LSST Corporation has 21 members
Brookhaven National Laboratory
California Institute of Technology
Columbia University
Google, Inc.
Harvard-Smithsonian Center for Astrophysics
Johns Hopkins University
Kavli Institute for Particle Astrophysics and Cosmology - Stanford University
Las Cumbres Observatory Global Telescope Network, Inc.
Lawrence Livermore National Laboratory
National Optical Astronomy Observatory
Princeton University
Research Corporation
Stanford Linear Accelerator Center
The Pennsylvania State University
Purdue University
The University of Arizona
University of California at Davis
University of California at Irvine
University of Illinois at Urbana-Champaign
University of Pennsylvania
University of Washington
LSST imaging & operations simulations
Sheared HDF raytraced +
perturbation + atmosphere +
wind + optics + pixel
Figure : Visits numbers per field for the 10 year simulated survey
LSST Operations, including real
weather data: coverage + depth
Performance verification using Subaru 15 sec imaging
Photometric Redshifts
LSST survey of 20,000 sq deg
• 4 billion galaxies with redshifts
• Time domain:
100,000 asteroids
1 million supernovae
1 million lenses
new phenomena
LSST Science Charts New Territory
Probing Dark Matter
And Dark Energy
Mapping the Milky Way
Finding Near Earth Asteroids
3-D Mass Tomography
2x2 degree mass map from Deep Lens Survey
Resolving galaxies
A given galaxy at high redshift should
appear smaller. But two effects oppose
this: cosmological angle-redshift relation,
and greater star formation in the past
(higher surface brightness).
Here are plots of galaxy surface
brightness vs radius (arcsec) in redshift
bins from z = 0.5 – 3.0 for 23-25 apparent
mag. At a surface brightness of 28 i
mag/sq.arcsec (horizontal dashed line)
most galaxies at z<3 are resolved in 0.6
arcsec FWHM seeing (vertical dashed
line).
HST/ACS GOODS, Ferguson 2007
Comparing HST with Subaru
ACS: 34 min (1 orbit)
PSF: 0.1 arcsec (FWHM)
2 arcmin
Comparing HST with Subaru
Suprime-Cam: 20 min
PSF: 0.52 arcsec (FWHM)
One quarter the diameter of the moon
DSS: digitized photographic plates
Sloan Digital Sky Survey
Deep Lens Survey
Massively Parallel Astrophysics
•
•
•
•
•
•
•
•
•
•
•
•
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Dark matter/dark energy via weak lensing
Dark energy via baryon acoustic oscillations
Dark energy via supernovae
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: unprecedented volume
Solar System Probes: Earth-crossing asteroids, Comets, TNOs
Key LSST Mission: Dark Energy
Precision measurements of all four dark energy
signatures in a single data set. Separately
measure geometry and growth of dark matter
structure vs cosmic time.
 Weak gravitational lensing correlations + CMB



(multiple lensing probes!)
Baryon acoustic oscillations (BAO) + CMB
Counts of dark matter clusters + CMB
Supernovae to redshift 1
(complementary to JDEM)
Critical Issues

WL shear reconstruction errors



Show control to better than required precision
using existing new facilities 
Photometric redshift errors

Develop robust photo-z calibration plan 

Undertake world campaign for spectroscopy ()
Photometry errors

Develop and test precision flux calibration
technique 
Distinguishing DE theories
Zhan
/0605696
Dark Energy Precision vs time
Separate DE Probes
Combined
Mass in CL0024
LSST will constrain
the nature of dark matter
in CL0024
LSST Mass
will measure
total neutrino mass
LSST WL+BAO+P(k) + Planck
LSST Science Collaborations
1. Supernovae: M. Wood-Vasey (CfA)
2. Weak lensing: D. Wittman (UCD) and B. Jain (Penn)
3. Stellar Populations: Abi Saha (NOAO)
4. Active Galactic Nuclei: Niel Brandt (Penn State)
5. Solar System: Steve Chesley (JPL)
6. Galaxies: Harry Ferguson (STScI)
7. Transients/variable stars: Shri Kulkarni (Caltech)
8. Large-scale Structure/BAO: Andrew Hamilton
(Colorado)
9. Milky Way Structure: Connie Rockosi (UCSC)
10. Strong gravitational lensing: Phil Marshall (UCSB)
http://www.lsst.org
LSST Ranked High Priority
• NRC Astronomy Decadal Survey
• NRC New Frontiers in the Solar System
• NRC Quarks-to-Cosmos
•
SAGENAP
• Quantum Universe
• Physics of the Universe
• Dark Energy Task Force + P5
sheared image
a = 4GM/bc2
DS
DLS
b
q
shear
DLS
g ~ q = D 4GM/bc2
S
Cosmology changes
geometric distance factors
Gravity & Cosmology change
the growth rate of mass
structure
Cosmic shear vs redshift
Shear Tomography
Shear spatial power spectra at redshifts to z  2.
0.01
z=0.2
0.001
Cosmology Fit Region
Linear regime
Non-linear regime
Needed shear sensitivity
CDM
z=3.2
Residual shear correlation
Test of shear systematics:
Use faint stars as proxies for
galaxies, and calculate the
shear-shear correlation after
correcting for PSF ellipticity
via a different set of stars.
Compare with expected
cosmic shear signal.
Conclusion: 200 exposures
per sky patch will yield
negligible PSF induced shear
systematics. Wittman (2005)
Cosmic shear signal
Stars
Cosmic Microwave Backgound
WMAP reveals a picture of the
fireball at the moment of
decoupling: redshift z = 1080
Temperature
Power 
• Characteristic
oscillations in
the CMB power
 Angular scale
Baryon Acoustic Oscillations
CMB (z = 1080)
RS~140 Mpc
Standard Ruler
Two Dimensions on the Sky
Angular Diameter Distances
Three Dimensions in Space-Time
Hubble Parameter
BAO (z < 3)