Welcome to the DES Weak Lensing Working Group

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## Welcome to the DES Weak Lensing Working Group

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**Welcome to the DES Weak Lensing Working Group**www.sarahbridle.net/deswlwiki deswlwiki Usual DES password (# eat with fish in UK)**Cosmic Lensing**gi~0.2 Real data: gi~0.03**Probes of Dark Energy**Cosmic Shear Evolution of dark matter perturbations Angular diameter distance Growth rate of structure Baryon Wiggles Standard ruler Angular diameter distance Supernovae Standard candle Luminosity distance Cluster counts Evolution of dark matter perturbations Angular diameter distance Growth rate of structure CMB Snapshot at ~400,000 yr Angular diameter dist to z~1000 Growth of structure (from ISW)**Surveys to measure Dark Energy**2020 2005 2010 KIDS Imaging CFHTLS DES LSST Euclid SKA SDSS VISTA JDEM SUBARU Pan-STARRS Euclid Wiggles DES SKA WiggleZ SDSS ATLAS WFMOS FMOS VISTA Supernovae CSP ESSENCE DES LSST CFHTLS JDEM Pan-STARRS Xeus Clusters AMI APEX SPT DES XCS SZA AMIBA ACT JDEM CMB WMAP3 WMAP5 Planck 2005 2010 2020**Actual schedule (I)**• 1.05pm Mike Jarvis • The point spread function of the Blanco Telescope • 1.45pm Mandeep Gill • LBT cluster lensing observations and DES cluster simulations • 2.10pm David Bacon • A flexion analysis of the DES PSF • 2.30pm Fabian Schmidt/Eduardo Rozo • Magnification effects in lensing measurements with DES • 2.50pm Coffee break**Actual schedule (II)**• 3.20pm Tom Diehl • DES CCDs • 3.45pm pm Bhuv/Sarah • Overview of recent activities • Interface with other working and study groups • Future activities of the Weak Lensing Working Group • 4pm Mike Jarvis, Erin Sheldon • The DES weak lensing pipeline • 5pm • Data Challenge 4 • Survey strategy**Overview of recent WLWG activities**• See previous talks • Science requirements document (many people) • Pipeline integration, image sims (esp Erin and Mike) • Survey strategy • Relevant more recent work by WLWG members • BCS – Tao, Mike • Forecasts including systematics – Gary • Non-Gaussian contributions – Bhuv • GREAT08, FLIP – several people**www.great08challenge.info**www.great08challenge.info**Future work of the WLWG (I)**• Improving and adding to the pipeline • New statistics • 3d mass maps via tomography • two-point statistics (including tomography): shear-shear correlations, Map2, Cl • three-point correlations: Map3? Others? • galaxy-shear cross-correlations (diagnostics?) • flexion • cluster mass maps • cluster counts: peaks? two point functions? • magnification/isw cross-correlations • topology measures**Future work of the WLWG (II)**• Questions: • Which of these topics has the best ability to test/fit for systematics? • Map2 and Map3 are useful in current measurements, how about other stats? • What do we want to test on image simulations for each of the next three years (i.e. before the start of the survey)? • N-body+ray tracing simulations. Barcelona group has some nice results already. High resolution sims? Calibrating analytical predictions?**Interface with other working and study groups**• The aim is to list areas that fall near the intersections with neighboring groups and to work out how to move forward on the most important of these e.g. by identifying the relevant contact people within other groups: • N-body Simulations • Combined Probes and Theory • Strong Lensing • Clusters • Photometric Redshifts • Large-scale Structure**N-body Simulations (Bhuv) Gus Evrard, Andrey Kravtsov**• People at the interface • Pablo Fosalba • Enrique Gaztanaga • Andrey Kravstov (official liason) • Topics at the interface • Multiple realisations to get covariance matrices • Non-linear theory as fn of cosmological parameters • Effects of baryon physics – mitigation techniques**Combined probes and theory Wayne Hu, Jochen Weller**• People at the interface • Jochen Weller • Topics at the interface • Covariance with other probes • Large scale structure • Clusters –defns of cluster mass • Inclusion of higher order statistics**Strong Lensing Liz Buckley-Geer, Martin Makler**• People at the interface • Lindsay King • Eduardo Cypriano • Martin Makler (official liason) • Topics at the interface • Cluster lensing using both strong and weak • Flexion • Combined tools within pipeline? • Common simulations?**Clusters (Sarah)Tim Mckay, Joe Mohr**• People at the interface • Erin Sheldon, Eduardo Cypriano, Vic Scarpine, Mandeep Gill, Tao Qian • Topics at the interface • Cluster masses and profiles from weak lensing • What do do with the masses – e.g. cosmology : cluster wg ? • What is the defn of mass that is used? • We use e.g. WL M_200 from NFW fit • Shear peak statistics**Photometric RedshiftsHuan Lin, Francisco Castander**• People at the interface • Filipe Abdalla • Zhaoming Ma • Erin Sheldon • Huan Lin (official liason) • Topics at the interface • Photoz accuracy – impact on cosmic shear • Knowledge of photoz accuracy**Large Scale Structure Enrique Gaztanaga, Will Percival**• People at the interface • Eduardo Rozo, Fabian Schmidt, Fernando Simoni, Erin Sheldon • Topics at the interface • Magnification bias • Galaxy-shear correlation function • Knowing the selection functions (masks) - STOMP • Cluster-shear correlation function • Constraints on photoz errors from galaxy clustering • Constraints on galaxy bias from combining with lensing**How will the WLWG access DC4?**• Testers • Tao Qian • Mandeep Gill • Donnacha Kirk (tbc) • Use web form interface?**What functionality is expected/required from the portal? (I)**• Positions • Shears • for each single image (and 2x2 error matrix), • multi exposure shear estimate per band (and errors) • Photozs: • P(z) per galaxy, • Error on P(z) (full matrix?) • Deconvolved shapelet coefs for 6th order fit (and errors) • Will derive flexions etc from these**What functionality is expected/required from the portal?**(II) • For Quality checks: • PSF shape and size • Multi-band magnitudes • Nearest neighbor distance • S/N • Deconvolved shapelet coefs for 6th order fit • Chisq from shapelet fit • Shear confidence flag (32 bits)**What functionality is expected/required from the portal for**DC-4? • Positions • Shears • for each single image • Photozs • Value and error • S/N • Deconvolved shapelet coefs for 6th order fit**What are our analysis plans for DC-4?**• Smoothed shear map • Shear estimate vs input galaxy shape • Shear estimate for each area with a continuous shear • As a function of magnitude, size • Shear correlation function (E, B) • Systematics checks • Star-galaxy shear correlation fns**Survey Strategy**• Effective number density as a function of position on sky • Inputs: exposure depth (10 sigma magnitude?) and psf fwhm • Output: neff • Erin has neff as function of seeing • http://sdss.physics.nyu.edu/esheldon/des/sensitivity/2007-11-21/des-s2n-predict-2007-11-21.pdf , Fig 3 bottom figures • We need to come up with a formula for how this scales with limiting magnitude – based on Gary’s simulations**Survey Strategy – Potential Plan I**Ingredients: • Formula for getting uncertainty on shear for given S/N, psf size, galaxy size – Gary? • Catalogue of galaxies: size, magnitude, z – COSMOS? - Gary?? (actually I have a version from Alexie Leathaud for Euclid too, but not sure the status of this) Intermediate data: • One augmented catalogue for each point on a grid of psf size, image depth • Catalogue now contains: size, mag, z, S/N, shear uncertainty**Survey Strategy – Potential Plan II**What Jim does for a given point on the sky • make a new combined catalogue which contains: • size, mag, z, total S/N, total ellipticity uncertainty where • total S/N is the quadrature sum of all bands • total ellipticity uncertainty is 1/(sum(1/sigma_i)) (i.e. usual weighted uncertainty) • neff is the number of galaxies meeting these criteria: • Total S/N (quadrature sum of all bands) >= 25 • Size >=1.1x PSF size (as measured by half-light radii) • Ellipticity uncertainty <=0.5**WLWG Plenary**• Random thoughts: • Summary of recent activities • CCD effects – our comments/ plans • Pre-DES WLWG projects draft list? • Show slides on interactions between wgs??**Draft Pre-DES WLWG Projects list**• Comparison of methods for getting 2 point function from a simulated shear catalogue • Shear catalogue is from simswg, of size~= DES • Includes different methods for mitigating systematics • Systematics checks e.g. star-galaxy 2 pt fn • 2 point statistics from DC-5 (warm up on DC-4) • As above for higher order statistics • Impact of DES CCD effects on measured shears • Mess up images in various ways • Use one or more shear measurement codes • Quality of DES optics (shear, flexion of psf) The above may lead to spin-off papers on new methods, which would not be “Pre-DES WLWG Projects”)**DES WLWG Key Projects**• 2 point function and standard LCDM cosmology constraints**DES WLWG Non-Key Project Science papers**• 3 point function and cosmological constraints • Tomographic density peak statistics • …**DES Key Projects with strong WLWG involvement, led by**another working group • Cosmological constraints from cluster counts, calibrated by cluster masses from lensing