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Galaxy Cluster Weak Lensing Pipeline Analysis Overview

Explore detailed processes of processing galaxy cluster weak lensing data. Includes image analysis, star selection, mass profile estimation, and comparison plan. Current work and previous mass estimates discussed with examples.

erica-nolan
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Galaxy Cluster Weak Lensing Pipeline Analysis Overview

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  1. OWLS Update OWLS Team January, 28 , 2008

  2. Overview • Last we met, we had presented parallel pipelines for the two methods • Since then we have been working back through each step in more detail • Today we zoom in on the first stage, and give a tentative plan to results we can compare against each other

  3. Diagrammatic Overview (FITS file) Image (Sextractor) Star Selection + Color Cut (IDL or command line tools) (PSF removal step) Imcat Shapelets Mass Profile (Final Result)

  4. Current Work • - Established zero point of magnitudes so we can understand exactly where we're making the cut • - Making 2D shear circulation pattern plots • - Running all 3 color filters all the way through (u,g,r) • - Making object match in WCS, so we can make color comparison and then color cut (A611: z=0.288, angular diam distance of 0.9 Gpc away in a flat cosmology, 4.30 kpc / arcsec  1Mpc ~ 233 arcsec ~ 4’  970 pixels for 0.24”/pixel)

  5. Some Previous A611 Mass Estimates “Cosmological constraints from the local X-ray luminosity function of the most X-ray-luminous galaxy cluster” by S.W. Allen, R. W. Schmidt, A.C. Fabian and H. Ebeling, MNRAS 2003 z= 0.288, r200= 2.56 +1.04 -.43 ( Mpc/h50), M200 = 13.1 +23.3 -5.5 (10^14 Msolar/h50) “CALIBRATION OF THE MASS–TEMPERATURE RELATION FOR CLUSTERS OF GALAXIES USING WEAK GRAVITATIONAL LENSING“, Pedersen and Dahle , ApJ 2007 M500c = 3.83+2.99 -2.79 (10^14 Msolar/h100)

  6. Example of previous WL analysis • Ran sextractor on 3 color filters (B,R,I) • Separated stars and galaxies • Make cuts on galaxies, trying to exclude cluster and foreground members (mag, color) • Clean stars (reject ellipticity > 0.2, and those very different from neighbors) and use these to estimate psf • Interpolate psf (using 5 nearest stars) • Correct for psf (using Im2Shape) (Bardeau et. al. 2005, A&A)

  7. Previous WL analysis, cont. • Estimate a mean bkgd galaxy redshift distribution (by matching to HDF-N catalog) • Use avg of psf-corrected ellipticity to estimate avg of shear • Make a 2D shearmap • Make a mass map (with lensent2) • Make radial profiles, fit to 3 models (SIS, power law, NFW) • Extract mass

  8. Brightest Pixel Magnitude vs. Object Magnitude Mu_Max vs Magnitude Mu_Max A1689, R band A611, G band

  9. Selecting Stars vs. Galaxies A611, G band A1689, R band (Bardeau et. al. 2005, A&A)

  10. Example of published red sequence (Bardeau et. al. 2007, A&A) Large circles are objects within 250” of cluster center – dominated by cluster members

  11. OurCluster Red Sequence (5751 matched objects in G and R filters; Squares are within 500 pixels of center)

  12. Magnitude Cut on galaxies Faint line: galaxies within 300’’ of cluster center, thick line, all galaxies.

  13. Sizes of stars after psf correction

  14. 2D Sextractor Ellipticity Plot Ellipticity Map before Deconvolution, from Sextractor

  15. 2D Shearmap post-psf deconvolution Shear Map After Deconvolution from Shapelets Shear Map After Deconvolution from Imcat

  16. Current Plan • Get common star / galaxy files to run through pipelines • Process separately, using same cuts • Make mass profiles • Fit to NFW curve, extract mass, radius, and concentration

  17. Conclusions • We understand initial inputs more thoroughly • Are currently working through getting a common sample of stars + galaxies to process through the 2 pipelines • Will detail those next steps carefully and compare pipeline results

  18. BACKUP SLIDES

  19. U-band star map U-band psf corrected star map

  20. G-band star map G-band psf corrected star map

  21. R-band star map R-band psf corrected star map

  22. Sextractor E-mode Sextractor B-mode Imcat B-mode Imcat E-mode

  23. Further parts of TDL • (At various stages of being done/implemented) • - Sort out dif in how shlets and imcat get orig ellip • - Implement bootstrap error and compare vs. ellip dispersion error • - Make profiles in shlets and imcat on non-matched objects separately • - Vary the center point we're taking profiles around, see how profiles vary ( moving 50 pixels in both x and y, changes first bin value by less than 0.01, similarly in all other bins, but changing just x by 100 pixels by 100 pixels makes the profile look like B-mode) • - Vary other cuts (radius, flux etc.) • - Make psf maps from stars for both pipelines, and compare • ----- Shlets • - Clean star selection for psf, excluding obviously bad stars • ----- Imcat • - Use a higher order psf interpolation

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