Galaxy-CMB and Galaxy-Galaxy Lensing on Large Scales: Sensitivity to Primordial Non-Gaussianity

A convincing detection of primordial non-Gaussianity in the local form of the bispectrum, whose amplitude is given by the ƒNL parameter, offers a powerful test of inflation. In this paper, we calculate the modification of two-point cross-correlation statistics of weak lensing—galaxy-galaxy lensing and galaxycosmic microwave background (CMB) crosscorrelation—due to ƒNL. We derive and calculate the covariance matrix of galaxygalaxy lensing, including cosmic variance terms. We focus on large scales (l < 100) for which the shape noise of the shear measurement becomes irrelevant and cosmic variance dominates the error budget. For a modest degree of non-Gaussianity, ƒNL = ±50 modifications of the galaxy-galaxy-lensing signal at the 10% level are seen on scales R ~ 300 Mpc, and grow rapidly toward larger scales as ∝ R2. We also see a clear signature of the baryonic acoustic oscillation feature in the matter power spectrum at ~ 150 Mpc, which can be measured by next-generation lensing experiments. In addition, we can probe the local-form primordial non-Gaussianity in the galaxy-CMB lensing signal by correlating the lensing potential reconstructed from CMB with high-z galaxies. For example, for ƒNL = ±50, we find that the galaxy-CMB lensing cross-power spectrum is modified by ~ 10% at l ~ 40, and by a factor of 2 at l ~ 10, for a population of galaxies at z = 2 with a bias of 2. The effect is greater for more highly biased populations at larger z; thus, high-z galaxy surveys cross correlated with CMB offer a yet another probe of primordial non-Gaussianity. Disciplines Physical Sciences and Mathematics | Physics Comments Suggested Citation: Jeong, D., E. Komatsu and B. Jain. (2009). "Galaxy-CMB and galaxy-galaxy lensing on large scales: Sensitivity to primordial non-Guassianity." Physical Review D. 80, 123527. © 2009 The American Physical Review. http://dx.doi.org/10.1103/PhysRevD.80.123527 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/physics_papers/44 Galaxy-CMB and galaxy-galaxy lensing on large scales: Sensitivity to primordial non-Gaussianity Donghui Jeong* and Eiichiro Komatsu Texas Cosmology Center and Department of Astronomy, University of Texas at Austin, 1 University Station, C1400, Austin, Texas 78712, USA