1. 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)

2. 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

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

4. 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)

5. 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)

6. ‘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

7. 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

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

9. 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:

10. 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

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

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

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

14. 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

15. 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

16. BACKUP Slides

17. 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

18. 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: