Effectiveness of halo and galaxy properties in reducing the scatter in the stellar-to-halo mass relation

TL;DR

This study investigates how various halo and galaxy properties influence the scatter in the stellar-to-halo mass relation across different mass ranges and simulation models, highlighting the roles of concentration, formation time, and black hole mass.

Contribution

It provides a detailed quantitative analysis of the factors affecting SHMR scatter in multiple simulations, revealing the varying importance of properties like concentration, formation time, and black hole mass.

Findings

Halo concentration and formation time influence scatter in low-mass haloes.

Galaxy SFR and age are primary drivers of scatter in intermediate-mass haloes.

Black hole mass becomes significant in high-mass haloes, with AGN feedback affecting scatter.

Abstract

The stellar-to-halo mass relation (SHMR) is a fundamental relationship between galaxies and their host dark matter haloes. In this study, we examine the scatter in this relation for primary galaxies in the semi-analytic L-Galaxies model and two cosmological hydrodynamical simulations, \eagle{} and \tng{}. We find that in low-mass haloes, more massive galaxies tend to reside in haloes with higher concentration, earlier formation time, greater environmental density, earlier major mergers, and, to have older stellar populations, which is consistent with findings in various studies. Quantitative analysis reveals the varying significance of halo and galaxy properties in determining SHMR scatter across simulations and models. In \eagle{} and \tng{}, halo concentration and formation time primarily influence SHMR scatter for haloes with $M_{\rm h}<10^{12}~\rm M_\odot$, but the influence diminishes at high mass. Baryonic processes play a more significant role in \lgal{}. For halos with $M_{\rm h} <10^{11}~\rm M_\odot$ and $10^{12}~\rm M_\odot<M_{\rm h}<10^{13}~\rm M_\odot$, the main drivers of scatter are galaxy SFR and age. In the $10^{11.5}~\rm M_\odot<M_{\rm h} <10^{12}~\rm M_\odot$ range, halo concentration and formation time are the primary factors. And for halos with $M_{\rm h} > 10^{13}~\rm M_\odot$, supermassive black hole mass becomes more important. Interestingly, it is found that AGN feedback may increase the amplitude of the scatter and decrease the dependence on halo properties at high masses.