The clustering and halo occupation distribution of Lyman-break galaxies at $z\sim4$

TL;DR

This study models the clustering of $z\, ext{~}4$ Lyman-break galaxies using a semi-analytical approach with AGN feedback, matching observations and exploring halo occupation and feedback effects.

Contribution

It introduces the first semi-analytical model with AGN feedback predicting LBG clustering and halo occupation at high redshift, aligning with recent survey data.

Findings

Model reproduces observed clustering trends within $3\sigma$

LBGs mainly in $10^{11}-10^{12}h^{-1}M_{\odot}$ haloes

Fewer bright satellite LBGs than observed at small scales

Abstract

We investigate the clustering of Lyman-break galaxies (LBGs) at $z\sim4$. Using the hierarchical galaxy formation model GALFORM, we predict, for the first time using a semi-analytical model with feedback from active galactic nuclei (AGN), the angular correlation function (ACF) of LBGs and find agreement within $3\,\sigma$ with new measurements of the ACF from surveys including the Hubble eXtreme Deep Field (XDF) and CANDELS field. Our simulations confirm the conclusion reached using independent models that although the predicted ACFs reproduce the trend of increased clustering with luminosity, the dependence is less strong than observed. We find that for the detection limits of the XDF field central LBGs at $z\sim 4$ predominantly reside in haloes of mass $\sim 10^{11}-10^{12}h^{-1}M_{\rm \odot}$ and that satellites reside in larger haloes of mass $\sim 10^{12}-10^{13}h^{-1}M_{\rm \odot}$. The model predicts fewer bright satellite LBGs at $z\sim4$ than is inferred from measurements of the ACF at small scales. By analysing the halo occupation distribution (HOD) predicted by the model, we find evidence that AGN feedback affects the HOD of central LBGs in massive haloes. This is a new high-redshift test of this important feedback mechanism. We investigate the effect of photometric errors in the observations on the ACF predictions. We find that the observational uncertainty in the galaxy luminosity reduces the clustering amplitude and that this effect increases towards faint galaxies, particularly on small scales. To compare properties of model with observed LBGs this uncertainty must be considered.