Day 925

Wednesday.


1507.03584
Improving reconstruction of the baryon acoustic peak: the effect of local environment
Achitouv, Blake

Precise measurements of he BAO scale as a standard ruler in the clustering pattern of LSS is a central goal of current and future galaxy surveys.  The BAO peak may be sharpened using the technique of density-field reconstruction, in which the bulk displacements of galaxies are estimated using Zel'dovich approximation.  Use numerical sims to demonstrate how the accuracy of this approximation depends strongly on local environment, and how this information may be used to construct an improved BAO measurement through environmental re-weighting and using higher-order perturbation theory.  Outline further applications of the displacement field for testing cosmo models.


1507.03906
Contamination of early-type galaxy alignments to galaxy lensing-CMB lensing cross-correlation
Chisari, Dunkley, Miller, Allison

Galaxy shapes are subject to distortions due to the tidal field of the Universe.  The cross-correlation of galaxy lensing with the lensing of CMB cannot easily be separated from cross-correlation of galaxy intrinsic shapes with CMB lensing.  Previous work suggested that the intrinsic alignment contamination can be 15% of this cross-spectrum of the CFHT Stripe 82 and ACT surveys.  Re-examine these estimates using up-to-date observational constraints of IA at a redshift more similar to that of CD82 galaxies.  Find a ~10% contamination of the cross-spectrum from red galaxies, with ~3% uncertainty due to uncertainties in the redshift distribution of source galaxies and the modeling of the spectral energy distribution.  Blue galaxies are consistent with being unaligned, but could contaminate the cross-spectrum by an additional 9.5% within current 95% CL.  While the fiducial estimate of alignment contamination is similar to previous work, the work suggests that the relevance of alignments for CMB lensing-galaxy lensing cross-correlation remains largely unconstrained.  Little information is currently available about alignment at z>1.2.  Consider the upper limiting case where all z>1.2 galaxies are aligned with the same strength as low z luminous red galaxies, finding as much as ~60% contamination.