Emulating galaxy clustering and galaxy-galaxy lensing into the deeply non-linear 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

41 Scopus citations


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 flexible 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 2 per cent constraint on the parameter combination σ8Ω0.6m, a factor of two better than a constraint that excludes non-linear scales (rp > 2 h-1 Mpc, 4 h-1 Mpc for γt, wp). Much of this improvement comes from the non-linear clustering information, which breaks degeneracies among HOD parameters. Increasing the effective source density to 3 arcmin-2 sharpens the constraint on σ8Ω0.6m by a further factor of two. With robust modelling into the non-linear regime, low-redshift measurements of matter clustering at the 1-per cent 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)
Pages (from-to)989-1006
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Mar 21 2019


  • Arge-scale structure of Universe
  • Cosmological parameters
  • Gravitational lensing: weak

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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