OWLS Pipeline Status Report STEP 2007 Workshop, JPL Mon, Aug 20, 2007 MSS Gill, J.Young, P. Martini, K. Honscheid, D. Weinberg, C. Kochanek , E. Rozo + OWLS Team ( OWLS = OSU Weak Lensing Survey)

Outline Introduction to OWLS project Description of hybrid approach Our current results from this approach Cuts on various galaxy properties and their effects on results Plans

OWLS Project Goals Constraining cosmological parameters with cluster weak lensing Picture of Abell 611 taken with the LBT

LBT OWLS Projections Projections for LBT with several clusters by next Autumn Assumes lensing using 50 richest clusters in observed 250 degree squared field with all background (lensed) galaxies at z=0.6 Colors are 1,2,3 s contours Here: s8 vs. Wm (Plot: J. Yoo)

Progress over the year.. We initially started the project thinking we would be able to basically use the shapelets code ‘out of the can’ to extract cluster shear But haven’t yet been able to get minimal KSB estimator to give us the known shears for STEP2 fields; we now know it has some instability (help from RJM and JB) So we came up with our own method to extract shear, which works decently well In hindsight, we have derived relations for ellipticity from shapelets which should be identical to sextractor values (see backup slide for more detail)

‘Hybrid’ Approach Seems slightly unorthodox, but we do it in 2 steps: For sextractor, we need to make pstamp recompositions of each object from shapelets Then separately sextract them, getting ellipticity for each object Deconvolve using shapelets Extract ellipticity averages using sextractor

Deconvolving with Extracted PSF We used the STEP2 starfields for the 6 individual psfs Extract psf in the standard way: pick stars, decompose them, fix fwhm and max decomposition order, decompose again Constant psf not assumed We then deconvolved the galaxy field with this psf model psf

Example of Deconvolved Galaxy (From STEP2 field: psfD, file shear20, object #1)

From deconvolved fields to shear extraction Use standard approach of plotting the difference of extracted shear and the input shear, vs. the input shear, for a given field Fit this to a line, and extract output c (y-intercept) and m (slope) values Example (psfA): Ellipticity per object:

Our Current Results – ADE Avg Average of PSF’s A,D,E – compared with STEP2 groups Squares = rotation-matched Triangles = original only Red square = our result

Our Current Results – PSF A Squares = rotation-matched, Triangles = original only Red square = our result

Our Current Results – PSF D Squares = rotation-matched, Triangles = original only Red square = our result

Our Current Results – PSF E Squares = rotation-matched, Triangles = original only Red square = our result

Variation with Cuts Significant variation in resulting c and m With varying cuts Here: vary a*b from 2 to 5 in steps of 0.5 Interested in learning how other groups came to their optimal sets of cuts

Plans Next: go to Subaru A1689 images Then to LBT images – currently have 2 clusters in hand Plan to get many more clusters from LBT time this coming year Ultimately extract cosmological parameters

BACKUP Slides

Results with Known PSF We initially used PSFs sent to us by J. Berge’ to get our technique working Example Plot of rotation-matched averaged c, m for D compared to paper, Red = ours

Cut effects on results Made cuts on several quantities (sexarea, sexflux, a*b, shapelets error) and saw results improve Example: change in m as function of shapelets error cut: