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LSST and JDEM as Complementary Probes of Dark Energy Tony Tyson, Andy Connolly, Zeljko Ivezic, James Jee, Steve Kahn, Sam Schmidt, Don Sweeney, Dave Wittman, Hu Zhan JDEM SCG Telecon November 25, 2008 Outline Science drivers Hardware implementation Systematics Simulations Synergy with JDEM 2 LSST survey of 20,000 sq deg • 4 billion galaxies with redshifts • Time domain: 1 million supernovae 1 million galaxy lenses 5 million asteroids new phenomena 3 LSST Survey 6-band Survey: ugrizy 320–1100 nm Frequent revisits: grizy Sky area covered: >20,000 deg2 0.2 arcsec / pixel Each 10 sq.deg field reimaged ~2000 times Limiting magnitude: 27.6 AB magnitude @5s 25 AB mag /visit = 2x15 seconds Photometry precision: 0.005 mag requirement 0.003 mag goal Key LSST Mission: Dark Energy Precision measurements of all dark energy signatures in a single data set. Separately measure geometry and growth of dark matter structure vs cosmic time. Weak gravitational lensing correlations (multiple lensing probes!) Baryon acoustic oscillations (BAO) Counts of dark matter clusters Supernovae to redshift 0.8 (complementary to JDEM) Probe anisotropy 5 6 8 3200 megapixel camera 9 Relative system throughput (%) LSST six color system Includes sensor QE, atmospheric attenuation, optical transmission functions Wavelength (nm) 10 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) 11 LSST reconstruction pipeline simulator xi ( AT A) 1 AT f o xi Perturbations Get correction vector by solving Normal equation. (A: sensitive matrix, f0: error vector.) 2W I1 1 I1 I 2 z I 1 I 2 Wedge I2 n 0 x WCS processing: get the perturbation wavefronts Get intra and extra focal image intensities. * Tools used for simulations and calculations: Zemax Matlab 12 Active optics Correct for perturbations due to thermal and mechanical distortions Each optic has 6 dof (decenter, defocus, three euler angles) Perturbations are placed on the three mirrors using a Zernike expansion to simulate the possible residual control system errors each mirror can have an arbitrary amplitude code goes up to 5th order polynomials e.g. Mirror Defocus Perturbation spectrum 13 FWHM Allocation & Budget meets SRD Requirements Margin available Some Telescope Thermal Effects Included No Explicit Camera Allocation For Thermal Effects 14 The LSST CCD Sensor 16 segments/CCD 200 CCDs total 3200 Total Outputs 15 Flatness metrology 16 The LSST site in Chile photometric calibration telescope 17 Seeing distribution 18 There are 24 LSSTC US Institutional Members Brookhaven National Laboratory California Institute of Technology Carnegie Mellon University Columbia University Google Inc. Harvard-Smithsonian Center for Astrophysics Johns Hopkins University Las Cumbres Observatory Lawrence Livermore National Laboratory National Optical Astronomy Observatory Princeton University Purdue University Research Corporation Rutgers University Stanford Linear Accelerator Center Stanford University –KIPAC The Pennsylvania State University University of Arizona University of California, Davis University of California, Irvine University of Illinois at Champaign-Urbana University of Pennsylvania University of Pittsburgh University of Washington + IN2P3 in France Funding: Public-Private Partnership NSF, DOE, Private 19 20 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 imaging 21 10-year simulation: limiting magnitudes per 30s visit in main survey 1 visit = 2 x 15 sec exposures Opsim5.72 Nov 2008 22 10-year simulation: number of visits per band in main survey Opsim5.72 Nov 2008 23 LSST and Cosmic Shear Ten redshift bins yield 55 auto and cross spectra useful range baryons + higher order 24 2-D Baryon Acoustic Oscillations 25 LSST Precision on Dark Energy [in DETF language] Combining techniques breaks degeneracies. Joint analysis of WL & BAO is less affected by the systematics 26 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 27 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. Cosmic shear signal Stars Compare with expected cosmic shear signal. Conclusion: 200 exposures per sky patch will yield negligible PSF induced shear systematics. Wittman (2005) 28 HST ACS data LSST: Gold sample: 4 billion galaxies i<25 (S/N=25), out of 10 billion detected. 56/sq.arcmin ~40 galaxies per sq.arcmin used for WL 29 residual galaxy shear correlation Single 10 sq.deg field full depth Galaxy residual shear error is shape shot noise dominated. Averages down like 1/N fields to the systematic floor. Survey of 20,000 sq.deg will have N ~ 2000 fields in each red band r, i, z Simulation of 0.6” seeing. J. Jee 2008 30 IMAGE SIMULATIONS Extended Sources Milkyway Transients Solar System Generate the seed catalog as required for simulation. Includes: Metadata Size Position Color Type Brightness Proper motion Variability Introduce shear parameter from cosmology metadata All Sky Database Defects Base Catalog Cosmology Instance Catalog Generation Source Image Generation Atmosphere Telescope Photon Propagation Operation Simulation DM Data base load simulation Generate per FOV Operation Simulation Camera Defects Formatting Generate per Sensor DM Pipelines Calibration Simulation LSST Sample Images and Catalogs 31 Input catalog for simulations Millennium Simulations Kitzbichler and White (2006) o o o o o o o o 6 fields, 1.4x1.4 deg per field 6x106 source per catalog Based on Croton et al (2006) and De Lucia and Blaizot (2006) models r<26 magnitude limit z<4 redshift limit BVRIK Johnson and griz SDSS Estimated u and y passbands Type and size included 32 32 Photo-z Simulations Abdalla etal. 2008 J=23.4 10 sigma 33 34 Calibrating photometric redshifts Cross-correlation LSS-based techniques can reconstruct the true z distribution of a photo-z bin, even with spectroscopy of only the brightest galaxies at each z. These techniques meet LSST requirements with easily attainable spectroscopic samples, ~104 galaxies per unit z. Newman 2008 35 Combining four LSST probes 36 Testing more general DE models 37 Probe anisotropy 38 multiple probes of dark energy • WL shear-shear tomography • WL bi-spectrum tomography • Distribution of 250,000 shear peaks • Baryon acoustic oscillations • 1 million SNe Ia, z<1 per year • Low l, 2p sky coverage: anisotropy? 3x109 galaxies, 106 SNe • probe growth(z) and d(z) separately • multiply lensed AGNs and SNe 39 JDEM-LSST Complementarity JDEM+LSST in 20,000 sq.deg and in fifty 10 sq.deg deep drilling fields Estimated cosmological constraints using LSST+JDEM Optimum strategy for joint DE mission risk reduction Priorities for max complementarity and cost effectiveness 40 JDEM+LSST 41 JDEM-LSST Priorities 1. 2. 3. 4. 5. Two IR bands from space. Deep, wide. Helps photo-z plus lots of astronomy (galaxy evolution, stellar) JDEM spectroscopic BAO complements LSST 2-D BAO JDEM coverage of same 20,000 sq.deg (see #1) Four near IR bands from space, closing the zY gap JDEM WL coverage of some of LSST’s survey area Need quantitative modeling for joint design mission. It will be useful to simulate the increase in FoM for each priority 42 extra slides 43 Requirement of integrated 50 galaxies per sq.arcminute: green line in the following plot. The corresponding 10 sigma limiting magnitudes in r and i are: r=25.6 i=25.0 AB mag 44 WL shear power spectrum and statistical errors Signal LSST: fsky = 0.5, ng = 40 SNAP: fsky = 0.1, ng =100 RMS intrinsic contribution to the shear σg= 0.25 (conservative). No systematics! Noise SNAP LSST Jain, Jarvis, and Bernstein 2006 gastrophysics 45 Trade with depth and systematics LSST only 46 Comparing HST with Subaru ACS: 34 min (1 orbit) PSF: 0.1 arcsec (FWHM) 2 arcmin 47 Comparing HST with Subaru Suprime-Cam: 20 min PSF: 0.52 arcsec (FWHM) 48 Galaxy ellipticity systematics in the SRD Specification: The median LSST image (two per visit) must have the median E1, E2, and Ex averaged over the FOV, less than SE3 for 1 arcmin, and less than SE4 for 5 arcmin. No more than EF2 % of images will exceed values of SE5 for 1 arcmin, nor SE6 for 5 arcmin 49 DETF FoM vs Etendue-Time Separate DE Probes Combined JDEM+LSST will be even better 50