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The Large Synoptic Survey Telescope and Precision Studies of Cosmology

The Large Synoptic Survey Telescope and Precision Studies of Cosmology. The LSST Collaboration. Brookhaven National Laboratory California Institute of Technology Google Corporation Harvard-Smithsonian Center for Astrophysics Johns Hopkins University Las Cumbres Observatory

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The Large Synoptic Survey Telescope and Precision Studies of Cosmology

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  1. The Large Synoptic Survey Telescopeand Precision Studies of Cosmology The LSST Collaboration 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 David L. Burke SLAC C2CR07 Granlibakken, California February 26, 2007

  2. Outline • The LSST Mission • The LSST Telescope and Camera • Precision Cosmology and Dark Energy • Schedule and Plans

  3. Concordance and Consternation Is LCDM 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?

  4. 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).

  5. Telescope and Camera 3.4m Secondary Meniscus Mirror 3.5° Photometric Camera 8.4m Primary-Tertiary Monolithic Mirror

  6. Primary mirror diameter Field of view 0.2 degrees 10 m 3.5 degrees Keck Telescope LSST Aperture and Field of View

  7. All facilities assumed operating100% in one survey Optical Throughput – Eténdue AΩ

  8. Telescope Optics 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.

  9. Similar Optical Mirrors and Systems SOAR 4.2m meniscus primary mirror Large Binocular Telescope f/1.1 optics with two 8.4m primary mirrors.

  10. Camera and Focal Plane Array Filters and Shutter ~ 2m Wavefront Sensors and Fast Guide Sensors 0.65m Diameter Focal Plane Array 3.2 Giga pixels “Raft” of nine 4kx4k CCDs.

  11. CCD Thickness (100mm) PSF Silicon Displacement: +10 mm 0 mm -10 mm Focal Plane Metrology Simulated LSST photon beam in silicon. Assembly-stage adjustment to achieve tolerance of 10 microns peak-to-valley surface flatness.

  12. Cerro Pachón LSST Site LSST Facility Sketch El Peñón Gemini South and SOAR

  13. More LSST Cosmology Highlights • Weak lensing of galaxies to z = 3. • Tomographic shear correlations in linear and • non-linear gravitational regimes. • Supernovae to z = 1. • Lensed supernovae and time delays. • Galaxies and cluster number densities as function of z. • Power spectra on very large scales k ~ 10-3h Mpc-1. • Baryon acoustic oscillations. • Power spectra on scales k ~ 10-1h Mpc-1.

  14. 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.

  15. Strong Lensing Galaxy at z =1.7 multiply imaged by a cluster at z = 0.4. A complete Einstein ring. Multiply imaged quasar (with time delays).

  16. Distortion matrix ( ) Distorted Image Source ξj with the co-moving coordinate along the geodesic, and a function of angular diameter distances.  ξi Convergence and Shear “Convergence” k and “shear” gdetermine the magnification and shape (ellipticity) of the image.

  17. Weak Lensing of Distant Galaxies Simulation courtesy of S. Colombi (IAP, France). Source galaxies are also lenses for more distant galaxies. Sensitive to cosmological distances, large-scale structure of matter, and the nature of gravitation.

  18. 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.

  19. 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.)

  20. 0.01 Needed Shear Sensitivity 0.001 Linear regime Non-linear regime Shear Power Spectra Tomography ΛCDM LSST designed to achieve 0.001 or better residual shear error.

  21. 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.

  22. Multi-Epoch Data Archive Average down instrumental and atmospheric statistical variations. Large dataset allows systematic errors to be addressed by subdivision.

  23. Multi-Epoch Data Archive Average down instrumental and atmospheric statistical variations. Large dataset allows systematic errors to be addressed by subdivision.

  24. LCDM shear signal Typical separation of reference stars in LSST exposures. Residual Shear Correlations Data from Subaru.

  25. Photometric Measurement of Redshifts “Photo-z’s” Galaxy Spectral Energy Density (SED) Moves left smaller z. Moves right larger z. “Balmer Break”

  26. Simulation photo-z calibration. Simulation of 6-band photo-z. sz 0.05 (1+z) sz 0.03 (1+z) Photo-z Calibration Calibrate with 20,000 spectroscopic redshifts. Need to calibrate bias and width to 10% accuracy to reach desired precision

  27. Precision on Dark Energy Parameters Measurements have different systematic limits. Combination is significantly better than any individual measurement.

  28. Project Schedule • Site Selection • Primary Mirror Contract (Arizona Mirror Lab) • Construction Proposals (NSF and DOE) • 2007-2009 Complete Engineering and Design • Long-Lead Procurements • 2010-2013 Construction and First Light • 2014 Commissioning and Science Done

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