A comparison of template vs. direct model fitting for redshift-space distortions in BOSS

TL;DR

This paper compares two leading methods for analyzing galaxy clustering data from BOSS to understand discrepancies in cosmological parameter estimates, highlighting the causes and implications for future surveys.

Contribution

It provides a detailed comparison of template fitting and direct modeling approaches for redshift-space distortions using BOSS data, clarifying their differences and impacts.

Findings

Differences in methods cause discrepancies in fluctuation amplitude estimates.

Isolating methodological causes helps improve future survey analyses.

Results inform best practices for modeling galaxy clustering.

Abstract

The growth of large-scale structure, as revealed in the anisotropic of clustering of galaxies in the low redshift Universe, provides a stringent test of our cosmological model. The strongest current constraints come from the BOSS and eBOSS surveys, with uncertainties on the amplitude of clustering of less than 10 per cent. A number of different approaches have been taken to fitting this signal, leading to apparently discrepant conclusions about the amplitude of fluctuations at late times. We compare in some detail two of the leading approaches, one based on a fitting a template cosmology whose amplitude and length scales are allowed to float with one based on a more traditional forward modeling approach, when fitting to the BOSS DR12 data. Holding the input data, scale cuts, window functions and modeling framework fixed we are able to isolate the cause of the differences and discuss the implications for future surveys.