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Testing the Shear Ratio Test: (More) Cosmology from Lensing in the COSMOS Field

Testing the Shear Ratio Test: (More) Cosmology from Lensing in the COSMOS Field. James Taylor University of Waterloo (Waterloo, Ontario, Canada). DUEL Edinburgh,

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Testing the Shear Ratio Test: (More) Cosmology from Lensing in the COSMOS Field

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  1. Testing the Shear Ratio Test: (More) Cosmology from Lensing in the COSMOS Field James Taylor University of Waterloo (Waterloo, Ontario, Canada) DUEL Edinburgh, Summer Conference July 18-23 2010

  2. The COSMOS SurveyP.I. Nick Scoville

  3. The COSMOS Survey • 2 square degree ACS mosaic • lensing results from 1.64 square degrees (~600 pointings) • 2-3 million galaxies down to F814WAB = 26.6 (0.6M to 26) • 30-band photometry, photo-zs with dz ~ 0.012(1+z) to z = 1.25 and IF814W = 24 • follow-up in X-ray, radio, IR, UV, Sub-mm, …

  4. WL Convergence Maps(cf. Rhodes et al. 2007; Massey et al. 2007; Leauthaud et al 2007) • cut catalogue down to 40 galaxies/arcmin2 to remove bad zs • correct for PSF variations, CTE • Get lensing maps, low-resolution 3D maps, various measures of power in 2D and restricted 3D • results compare well with baryonic distributions (e.g. galaxy distribution)

  5. The Final Result: E-modes (left) versus B-modes (right)

  6. The Final Result: 3-D constraints on the amplitude of fluctuations: recent updates: - improved photo-zs - improved CTE correction in images - new shear calibration underway + updated group catalog(s) so expect stronger signal around peaks in lensing map, and cleaner dependence on source and lens redshift  time for some 2nd generation tests of the lensing signal Massey et al 2007

  7. Measuring Geometry: Shear Ratio Test (Jain & Taylor 2003, Bernstein & Jain 2004, Taylor et al. 2007) Take ratio of shear of objects behind a particular cluster, as a function of redshift Details of mass distribution & overall calibration cancel  clean geometric test Can extend this to continuous result by fitting to all redshifts Z(z)  DLS/DS Relative Lensing Strength Z(z) Your cluster goes here Bartelmann & Schneider 1999

  8. But how big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Use strength of signal behind cluster as a function of redshift to measure DA(z):

  9. How big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Lens at z = 0.2 Use strength of signal behind cluster as a function of redshift to measure DA(z): weak but distinctive signal; relativechange (change in distance ratio)is only 0.5% 0.5% relative change

  10. How big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Lens at z = 0.3 Use strength of signal behind cluster as a function of redshift to measure DA(z): weak but distinctive signal; relativechange (change in distance ratio)is only 0.5% 0.5% relative change

  11. How big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Lens at z = 0.5 Use strength of signal behind cluster as a function of redshift to measure DA(z): weak but distinctive signal; relativechange (change in distance ratio)is only 0.5% 0.5% relative change

  12. How big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Lens at z = 0.7 Use strength of signal behind cluster as a function of redshift to measure DA(z): weak but distinctive signal; relativechange (change in distance ratio)is only 0.5% 0.5% relative change

  13. How big is the signal? Base: h = 0.73, m = 0.27 ( or X = 1 - m) Variants (different curves): m = 0.25,0.30,0.32 w0 = -1,-0.95,-0.9,-0.85,-0.8 w(z) = w0 + wa(1-a) with w0 = -1, wa = 0.05, 0.1 h = 0.7, 0.75 Signal weak but distinctive Lens at z = 1.0 Use strength of signal behind cluster as a function of redshift to measure DA(z): weak but distinctive signal; relativechange (change in distance ratio)is only 0.5% 0.5% relative change

  14. Previous detections with massive clusters Signal has been seen previously behind a few clusters: e.g. Wittman et al. 2001 ~3e14 Mo cluster in DLS; detection, mass and redshift all from weak lensing (source photo-zs from 4 bands)

  15. Previous detections with massive clusters Signal has been seen previously behind a few clusters: e.g. Gavazzi & Soucail (2008): cluster Cl-02 in CFHTLS-Deep (cf. also Medezinski et al. submitted: 1.25 M galaxies behind 25 massive clusters, in a few bands)

  16. So why try this in COSMOS ? Less signal (groups only, no truly massive clusters), but far better photo-zs can push techniques down to group or galaxy scales nice test of systematics in catalogue selection, effect of photo-z errors test/confirm error forecasts for future surveys Percival et al .2007: interesting indication of possible mismatch in distance scales in BAO?

  17. The sample of COSMOS Groups and Clusters (X-ray derived Mass) Log(volume) (plot from Leauthaud et al. 2009)

  18. ~67  in top 14 objects? The sample of COSMOS Groups and Clusters (X-ray derived Mass) Log(volume) (plot from Leauthaud et al. 2009)

  19. could get another ~60  from less massive groups? The sample of COSMOS Groups and Clusters (X-ray derived Mass) Log(volume) (plot from Leauthaud et al. 2009)

  20. Shear vs. photo-z around peaks, along promising lines of sight

  21. Shear vs. photo-z around peaks, along promising lines of sight

  22. How to stack clusters? Tangential shear goes as: so redshift dependence enters via critical surface density: Thus if we define (assumes flat models) and then independent of cosmology

  23. We see the signal! Stack of regions within 6’ of ~200+ x-ray groups good fit in front of/behind cluster significance still unclear; seems less than expected effect of other structures along the line of sight decreases chi2, but hard to quantify

  24. A Caveat In a field this small, a few redshifts dominate the distribution of structure  systematics in shear ratio

  25. Signal detected, well behaved, significance slightly lower than expected? • Still studying noise versus radial weighting, catalogue cuts, path weighting • Results roughly consistent with w0 ~ -1.0 +/- 1.0 • Future predictions for large surveys + CMB + BAO (Taylor et al. 2007): • w0 = 0.047, wa = 0.111 and 2% • measurement of dark energy at • z ~ 0.6 • Or use CMB as an extra slice? • (cf. Hu, Holz & Vale 2007; • Das & Spergel 2009) Prospects error forecasts from 20,000 deg2 survey (Taylor et al. 2007)

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