Perturbation theory models for LSST-era galaxy clustering: tests with
  sub-percent mock catalog measurements in Fourier and configuration space
  We analyze the clustering of galaxies using the z=1.006 snapshot of the
CosmoDC2 simulation, a high-fidelity synthetic galaxy catalog designed to
validate analysis methods for the Large Synoptic Survey Telescope (LSST). We
present sub-percent measurements of the galaxy auto-correlation and galaxy-dark
matter cross correlations in Fourier space and configuration space for a
magnitude-limited galaxy sample. At these levels of precision, the statistical
errors of the measurement are comparable to the systematic effects present in
the simulation and measurement procedure; nevertheless, using a hybrid-PT
model, we are able to model non-linear galaxy bias with 0.5% precision up to
scales of $k_{\rm max}= 0.5 \ h/{\rm Mpc}$ and $r_{\rm min}= 4 \ {\rm Mpc}/h$.
While the linear bias parameter is measured with 0.01% precision, other bias
parameters are determined with considerably weaker constraints and sometimes
bimodal posterior distributions. We compare our fiducial model with lower
dimensional models where the higher-order bias parameters are fixed at their
co-evolution values and find that leaving these parameters free provides
significant improvements in our ability to model small scale information. We
also compare bias parameters for galaxy samples defined using different
magnitude bands and find agreement between samples containing equal numbers of
galaxies. Finally, we compare bias parameters between Fourier space and
configuration space and find moderate tension between the two approaches.
Although our model is often unable to fit the CosmoDC2 galaxy samples within
the 0.1% precision of our measurements, our results suggest that the hybrid-PT
model used in this analysis is capable of modeling non-linear galaxy bias
within the percent level precision needed for upcoming galaxy surveys.
