# Modelling the tightest relation between galaxy properties and dark matter halo properties from hydrodynamical simulations of galaxy formation

## TL;DR

This study identifies the stellar mass at peak circular velocity as the best predictor of galaxy properties, demonstrating that simple models like SHAM can effectively predict galaxy clustering despite inherent scatter.

## Contribution

It reveals that stellar mass at peak circular velocity provides the tightest galaxy-halo relation across all galaxy types, including satellites, and shows the minimal impact of scatter on clustering predictions.

## Key findings

- Stellar mass at peak circular velocity yields the tightest galaxy-halo correlation.
- Evolution correction reduces scatter in the galaxy-halo relation.
- Simple SHAM models can accurately predict galaxy clustering despite scatter.

## Abstract

We investigate how a property of a galaxy correlates most tightly with a property of its host dark matter halo, using state-of-the-art hydrodynamical simulations of galaxy formation EAGLE, Illustris, and IllustrisTNG. Unlike most of the previous work, our analyses focus on all types of galaxies, including both central and satellite galaxies. We find that the stellar mass of a galaxy at the epoch of the peak circular velocity with an evolution correction gives the tightest such correlation to the peak circular velocity $V_{\rm peak}$ of the galaxy's underling dark matter halo. The evolution of galaxy stellar mass reduces rather than increases scatter in such a relation. We also find that one major source of scatter comes from star stripping due to the strong interactions between galaxies. Even though, we show that the size of scatter predicted by hydrodynamical simulations has a negligible impact on the clustering of dense $V_{\rm peak}$-selected subhalo from simulations, which suggests that even the simplest subhalo abundance matching (SHAM), without scatter and any additional free parameter, can provide a robust prediction of galaxy clustering that can agree impressively well with the observations from the SDSS main galaxy survey.