Day 1311

Friday.

1709.07099
Emulating galaxy clustering and galaxy-galaxy lensing into the deeply nonlinear regime: methodology, information, and forecasts
Wibking, et al

The combination of GGL with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low z.  Show that extending clustering+GGL analyses from the linear regime down to ~0.5 Mpc/h 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 sims, construct a Taylor-expansion emulator that predicts the galaxy autocorrelation xi_gg(r) and galaxy-matter cross-correlation xi_gm(r) as a function of sigma8, Omega_m, and halo occupation distribution parameters, which are allowed to vary with large scale environment to represent possible effects of galaxy assembly bias.  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<=r_p<=30 Mpc/h yields a 1.8% constraint on the parameter combination of sigma8 Omega_m^0.58, a factor of two better than a constraint that excludes non-linear scales (r_p>2Mpc/h, 4Mpc/h for gamma_t, w_p).  Much of the improvement comes from the non-linear clustering information, which break 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 sigma8 Omega_m^0.58 by a further factor of two.  With robust modeling into the non-linear regime, low redshift measurements of matter clustering at the 1% level with clustering+GGL alone are well within reach of current data sets such as those provided by the DES.