The Large Synoptic Survey Telescope

1. The Large Synoptic Survey Telescope LSST Philip A. Pinto Steward Observatory University of Arizona & The LSST Collaboration

2. A Window on New Physics Cosmological observations provide evidence for physics beyond the standard model: • 96% of the mass-energy of the universe is non-baryonic • 2/3 of the mass-energy is “dark energy” • Most of the rest is non-baryonic “cold dark matter” Observations provide two (related) lines of evidence: • Expansion history of the universe • Clustering history of the universe

3. Expansion History Hubble’s diagram: (E. Hubble 1929, Proc. Nat. Acad. Sci. 15, p. 168.)

4. “Who blows up the ball? What makes the universe expand, or swell up? That is done by the Lambda. Another answer cannot be given.” - Prof. Dr. W. de Sitter

5. Blowing up the ball… Because pressure contributes stress-energy, the expansion rate is We have acceleration if Lorentz invariance of the vacuum stress-energy tensor requires Vacuum energy density has

6. Take the simplest expression for the cosmic equation of state, As the universe expands, Regular matter: Relativistic matter: Cosmological constant: Today’s expansion rate: Fraction of component i:

7. In a Friedman-Robertson-Walker universe, luminosity distance is

8. Cosmological constant, or… A cosmological constant has w = -1, constant in time. If dark energy were, e.g., to be associated with a new scalar field, then w might be a function of the cosmic scale factor. Current work parameterizes this as w(a) = w0 + wa (1-a) At present, data are consistent with w0 = -1 to 10-20%, and cannot meaningfully constrain wa. There are many other possibilities…

9. Clustering History The initial conditions of the universe were quite smooth, with small fluctuations in density (Δ/10-3) Denser regions collapse, attracting the material around them, leading to the formation of structure. Initial “blue” Pk spectrum smoothed by diffusion of hot components. The nature of the structure is determined by Competition between gravitational collapse and cosmic expansion The nature of the expanding fluid(s)

10. Clustering History Measuring the properties of the clustering thus give a different way to measure the expansion history (albeit less directly). Clustering properties and evolution also provides information on the nature of the fluid: e.g.: is dark matter really a collisionless fluid?

11. LSST: Windows on the Dark Sector LSST is a facility which can address all of these questions through multiple, complimentary techniques, using the same set of data, acquired in the same survey. (Neat astronomy, too!)

12. Science Goals Survey system Site Designing an all-purpose survey Basic figure of merit for surveys is the number of objects detected, per unit time, to a given S/N:

13. Science Potential Detailed operational simulations show that a survey with AΩ > 300, operating for 10 years, can simultaneously provide major improvements on a wide variety of fronts. • Probe dark energy and dark matter • 2% constraints on (current!) DE parameters by many independent means: multiple weak lensing, BAO, supernovæ • Open the time domain by a factor of > 1000 • Faint transient sources: SNe, GRB afterglows, … • Variable sources: stars, AGN, strong lensing, … • Solar system probes, esp. of faint, fast-moving objects • NEAs, KBOs, comets, debris

14. Science Potential THE UNKNOWN Such a system will gather many times more optical data than all previous astronomical images combined. Finding now-rare events will become commonplace. Finding the truly singular will be possible.

15. The LSST System AΩ = 319 m2 deg2 Data Management ~30 TB/night 50 PB in ten years 8.4m Telescope 3.5° field of view 3.2 Gigapixel Camera 2 second readout

16. The LSST System LSST is designed to go wide – deep – fast • ~10 deg2 per field • ~6.5m effective collecting aperture • 24.5 AB r-band mag per 15 sec. exposure (2 per pointing) (~30 photons, ~10 eV from a source perhaps 1028 cm distant) • wide coverage > 20,000 square degrees of sky • multiple UV, optical, near-IR filters: ugrizy • 1100 epochs in each of >2000 fields, over ten years • accumulated depth of 24-26 AB magnitude (10 σ) in each filter

17. A qualitatively different regime

18. Optical Design • Modified Paul-Baker 3-Mirror Telescope • F/1.23 with <0.20 arcsec FWHM images in ugrizy • 3.5 ° FOV and Etendue = 319 m2deg2 • All Optics Manufacturing Within State of the Art

19. Telescope 5 second slew + settle Altitude of Azimuth Configuration Compact Stiff Structure Camera and Secondary Mirror in Top End

20. 6 x Hexapod Actuator (Grey) 102 x Axial Actuator (Green) Mirror Cell (Yellow) 6 x Tangent Actuator (Red) Primary Surface 8.4 Meters Secondary Mirror (Light Blue) Baffle (Black) Tertiary Surface 0.9 Meters Challenging Large Optics • Unique Monolithic Mirror: Primary and Tertiary Surfaces Polished Into Same Substrate • Cast Borosilicate Design • Thin Meniscus Low Expansion Glass Design for Secondary Mirror • 102 Support Actuators

21. Construction has already begun… The contract for the primary mirror: privately funded awarded to the Steward Observatory Mirror Lab. LBT1 primary

22. Camera 64 cm diameter active area 3 Gigapixels with 2 second read-out Five filters in camera Inner dewar w/ FPA Lenses larger than Yerkes refractor Curtain shutter 106 duty cycle 0.74m filters

23. Bay 14 Bay 04 Bay 19 Bay 19 Bay 09 Bay 24 Bay 23 Bay 18 Bay 13 Bay 08 Bay 03 Bay 18 Bay 07 Bay 17 Bay 12 Bay 22 Bay 17 Bay 02 Bay 16 Bay 06 Bay 16 Bay 11 Bay 21 Bay 01 Bay 10 Bay 15 Bay 15 Bay 05 Bay 00 Bay 20 Focal Plane Layout 201 4x by 4x CCDs Wavefront Sensors (4 locations) Guide Sensors (8 locations) 3.5 degree Field of View (634 mm diameter) CCS +Y CCS +X CCS +Z

24. Camera Assembly

25. LSST Data System 30 Gbps peak from camera 6 Gbps sustained rate to DP system 30 TBytes/night In ten years, 50 Petabyte, time-tagged imaging database 100 Terabyte photometric catalog real-time processing: 40 TeraFlop data distribution system(s) Data management is LSST’s greatest challenge

26. LSST Data System Infrastructure Archive Computing Center 50 PB disk 25 TFLOP Mirror Sites 103 to 4 km 3 Gb/s GRID, Internet 2 GRID, Internet 2 Portal User Portal Users 103 to 4 km 3 Gb/s Portal Users 10-1 km, 5 Gb/s Telescope Site Base Camp Center Focal plane 150 TB disk 10 TFLOP 101 to 2 km 10 Gb/s 15 TB disk, 5 TFLOP Notes: B = bytes, b = bits

27. LSST Data System Data Acquisition Image Processing Pipeline Detection Pipeline Association Pipeline Alerts Image Archive Detection Catalog Object Catalog VO Compliant Interface

28. LSST Data Calibrated Image Data • Deep co-added images • >20,000 square degrees to 24-26 AB mag (10σ) • six filters ugrizy • Individual images to 24.5 AB mag (10σ, r-band) • Difference images • Metadata • control system • automated quality assessment • world coordinate system

29. LSST Data Calibrated Object Database • Raw source detections • Object data • Photometry • Lightcurves • Parallax/proper motion • Shape parameters • Classification Alert notification system • Automated alerts based upon selected criteria • Notification w/in 1 minute of observation

30. ALL DATA ARE PUBLIC Project is committed to a completely “open-data” mode of operation, once science operations commence. No proprietary data. No proprietary data periods. Period. Data will appear in the public archives within hours of acquisition. Methods of accessing the data will likely evolve over time, depending on the evolution of the international data infrastructure.

31. Site: CerroPachón, Chile

32. Overview LSST Site(El Peñón) Gemini SOAR

33. LSST Key Science • The “Dark Sector” * • weak lensing, supernovae, BAO, cluster counting • Finding and Exploiting Optical Transients • Novæ, SNe, GRB’s, μ-lensing, variables, AGN • Mapping the Solar System • NEA, KBO, TNO, comets, debris • The Structure of our Galaxy • Structure & formation of the halo • Mapping the dark halo through dynamical tracers • Survey of the solar neighborhood

34. Lensing sheared image galaxy b intervening mass shear: Cosmology changes the growth rate of mass structure Cosmology changes geometric distance factors

35. Sheared galaxies…

36. Cluster detection via WL shear 2-degree by 2-degree mass map of one of five DLS fields. All four clusters examined in this field have been verified with spectroscopy and X-ray observations.

37. Mass in CL0024 Stuff

38. Disagrees with CDM models. Is the Dark Sector complicated? Are there interactions?

39. Cluster Counts Precision and accuracy are increased by using optimal filter and S/N threshold rather than mass threshold for cluster determination. LSST 10 yr survey: 3x109 galaxies after Wang et al., 2004

40. Correlation Tomography 2- and 3-point correlation tomography with LSST’s billions of source galaxies plus Planck. A statistically independent and complementary constraint on dark energy. after Takada & Jain, 2004 Photometric Redshifts!

41. Photometric Redshifts

42. Baryon Acoustic Oscillations

43. BAO Detection: SDSS red galaxies Eisenstein et al. (2005)

44. BAO as a Standard Ruler CMB + RS~150 Mpc Angular diameter distance & Hubble parameter (Sound horizon at recombination) (Angular & radial scales)

45. Prospects: Power Spectrum 0.2 < z < 3, 7 redshift bins LSST Errors are dominated by sample variance (volume) at low-z and shot noise (number density) at high-z. For photo-z surveys, szreduces the number of modes. See alsoBlake & Bridle (2005).

46. Comparison of probes • CMB priors & WK=0 • BAO constraints are competitive. • A large rms photo-z error is tolerable; the key is the uncertainty in sz. Zhan & Knox (astro-ph/0509260)

47. CMB + BAO + Shear Tomography

48. Curvature? The Need for High-z Data • CMB priors • High-z data not critical if WK is fixed • High-z data crucial if WK unknown • Behavior of the constraints depends on the survey and redshift errors • See also Weller & Albrecht (2001) and Linder (2005) for discussions on SNe data 1000 sq deg spectroscopic survey: w0—wa degrades quite a bit if no high-z data; even worse if WK is unknown.

49. Supernova Cosmology 1 million SNe Ia lightcurves will allow discovering systematic effects in the luminosity-width relation. ~10,000 SNe Ia are sufficient to measure w to 1%. → provide w along 250 independent directions New physics? Tilted Universes? SN SNe Ia measurements of H(z) complement those from weak lensing and CMB: WL

50. -0.9 w0 -1.0 -1.1 0.26 0.30 0.34 Ωm Supernova Cosmology 10 min./night on one field will measure >6000 type Ia supernovæ per year to z>1 using photo-z’s from SNe and galaxies