Day 1179

Monday.  Tuesday.

1610.09410
Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS
Alam, Miyatake, More, Ho, Mandelbaum

Measure a combination of gravitational lensing, galaxy clustering, and z-space distortions called E_G.  The quantity E_G probes both parts of metric potential and is insensitive to galaxy bias and sigma_8.  These properties make it an attractive statistic to test LCDM, GR and its alternate theories.  Combined CMASS DR11 with CFHTLenS and recent measurements of beta from RSD analysis, and find E_G(z=0.57)=0.42±0.056, a 13% measurement in agreement with the prediction of general relativity E_G(z=0.57)=0.396±0.011 using the Planck 2015 cosmo parameters.  Corrected the measurement for various observational and theoretical systematics.  The measurement is consistent with the first measurement of E_G using CMB lensing in place of galaxy lensing (Pullen+2015) at small scales, but shows 2.8 sigma tension when compared with their final results including large scales.  This analysis with future surveys will provide improved statistical error and better control over systematics to test GR and its alternate theories.


1610.09828
Testing PSF interpolation in weak lensing with real data
Lu, Zhang, et al

Reconstruction of the PSF is a critical process in WL measurement.  Develop a real-data based and galaxy-oriented pipeline to compare the performances of various PSF reconstruction schemes. Making use of a large amount of CFHTLenS data, the performances of 3 classes of interpolating schemes - polynomial, Kriging, and Shepard - are evaluated.  Find that polynomial interpolations with optimal orders and domains perform the best.  Quantify the effect of the residual PSF reconstruction error on shear recovery in terms of the multiplicative and additive biases, and their spatial correlation using the shear measurement method of Zhang+2015.  Find that the impact of PSF reconstruction uncertainty on the shear-shear correlation can be significantly reduced by cross correlating the shear estimators from different exposures.  It takes only 0.2 stars (SNR>100) per square arcmin on each exposure to reach the best performance of PSF interpolation, a requirement that is generally satisfied in the CFHTLenS data.