The Concentration Dependence of the Galaxy-Halo Connection: Modeling Assembly Bias with Abundance Matching

TL;DR

This paper introduces a new parameterization for abundance matching that models assembly bias by interpolating between halo mass and circular velocity, enabling better galaxy-halo connection modeling.

Contribution

The authors develop a novel, smooth interpolation scheme for abundance matching that allows adjustable assembly bias based on halo concentration dependence.

Findings

The new model can reproduce observed galaxy clustering and satellite fractions.

SDSS data constrains the concentration dependence and scatter in the model.

Larger simulation volume reduces sample variance in measurements.

Abstract

Empirical methods for connecting galaxies to their dark matter halos have become essential for interpreting measurements of the spatial statistics of galaxies. In this work, we present a novel approach for parameterizing the degree of concentration dependence in the abundance matching method. This new parameterization provides a smooth interpolation between two commonly used matching proxies: the peak halo mass and the peak halo maximal circular velocity. This parameterization controls the amount of dependence of galaxy luminosity on halo concentration at a fixed halo mass. Effectively this interpolation scheme enables abundance matching models to have adjustable assembly bias in the resulting galaxy catalogs. With the new 400 Mpc/h DarkSky Simulation, whose larger volume provides lower sample variance, we further show that low-redshift two-point clustering and satellite fraction measurements from SDSS can already provide a joint constraint on this concentration dependence and the scatter within the abundance matching framework.