The dependence of subhalo abundance matching on galaxy photometry and selection criteria

TL;DR

This paper investigates how the choice of galaxy photometry and selection criteria affect subhalo abundance matching (SHAM) results, introducing a new parametrisation and providing best-fit parameters to improve model accuracy.

Contribution

The study introduces a new SHAM parametrisation and derives best-fit parameters based on various galaxy selection and photometric definitions, enhancing model robustness.

Findings

Scatter in galaxy-halo connection increases at the faint end.

SHAM performs better with luminosity than stellar mass.

Optically- and HI-selected galaxy SHAM parameters are mutually exclusive.

Abstract

Subhalo abundance matching (SHAM) is a popular technique for assigning galaxy mass or luminosity to haloes produced in N-body simulations. The method works by matching the cumulative number functions of the galaxy and halo properties, and is therefore sensitive both to the precise definitions of those properties and to the selection criteria used to define the samples. Further dependence follows when SHAM parameters are calibrated with galaxy clustering, which is known to depend strongly on the manner in which galaxies are selected. In this paper we introduce a new parametrisation for SHAM and derive the best-fit SHAM parameters as a function of various properties of the selection of the galaxy sample and of the photometric definition, including S\'ersic vs Petrosian magnitudes, stellar masses vs r-band magnitudes and optical (SDSS) vs HI (ALFALFA) selection. In each case we calculate the models' goodness-of-fit to measurements of the projected two-point galaxy correlation function. In the optically-selected samples we find strong evidence that the scatter in the galaxy-halo connection increases towards the faint end, and that AM performs better with luminosity than stellar mass. The SHAM parameters of optically- and HI-selected galaxies are mutually exclusive, with the latter suggesting the importance of properties beyond halo mass. We provide best-fit parameters for the SHAM galaxy-halo connection as a function of each of our input choices, extending the domain of validity of the model while reducing potential systematic error in its use.