Emulating galaxy clustering and galaxy-galaxy lensing into the deeply nonlinear regime: Methodology, information, and forecasts

Benjamin D. Wibking, Andrés N. Salcedo, David H. Weinberg, Lehman H. Garrison, Douglas Ferrer, Jeremy Tinker, Daniel Eisenstein, Marc Metchnik, Philip Pinto

Research output: Contribution to journalArticlepeer-review


The combination of galaxy-galaxy lensing (GGL) with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low redshifts. We show that extending clustering+GGL analyses from the linear regime down to ∼0:5 h-1 Mpc scales increases their constraining power considerably, even after marginalizing over a exible model of non-linear galaxy bias. Using a grid of cosmological N-body simulations, we construct a Taylor-expansion emulator that predicts the galaxy autocorrelation Ξgg(r) and galaxy-matter cross-correlation Ξgm(r) as a function of σ8,Ωm, and halo occupation distribution (HOD) parameters, which are allowed to vary with large scale environment to represent possible effects of galaxy assembly bias. We present forecasts for a fiducial case that corresponds to BOSS LOWZ galaxy clustering and SDSS-depth weak lensing (effective source density ∼0:3 arcmin-2). Using tangential shear and projected correlation function measurements over 0:5 ≤ rp ≤ 30 h-1 Mpc yields a 1.8% constraint on the parameter combination σ80:58 Ωm , a factor of two better than a constraint that excludes non-linear scales (rp > 2 h-1 Mpc, 4 h-1 Mpc for t; wp). Much of this improvement comes from the non-linear clustering information, which breaks degeneracies among HOD parameters that would otherwise degrade the inference of matter clustering from GGL. Increasing the effective source density to 3 arcmin-2 sharpens the constraint on _80:58 m by a further factor of two. With robust modeling into the non-linear regime, low-redshift measurements of matter clustering at the 1-percent level with clustering+GGL alone are well within reach of current data sets such as those provided by the Dark Energy Survey.

Original languageEnglish (US)
JournalUnknown Journal
StatePublished - Sep 20 2017


  • Cosmology
  • Large scale structure
  • Weak lensing

ASJC Scopus subject areas

  • General

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