Tracing the Formation History of Intrahalo Light with Horizon Run 5

TL;DR

This study uses the Horizon Run 5 simulation to trace the origins and formation history of intrahalo light, revealing dominant channels and their evolution over cosmic time.

Contribution

It provides a detailed classification of IHL origins, highlighting the dominant role of BHG mergers and the evolution of stripping and pre-processing channels.

Findings

Over 60% of IHL originates from BHG mergers.

Pre-processing accounts for over 20% of IHL.

Stripping becomes significant at redshift z<4.

Abstract

We investigate the formation history of intrahalo light (IHL) using the high-resolution (~1 kpc), large-scale (~Gpc) cosmological hydrodynamical simulation, Horizon Run 5 (HR5). IHL particles are identified by carefully considering both their binding energies and positions with respect to the tidal radii of individual galaxies. By analyzing more than 1,200 galaxy groups and clusters with $\geq 10^{13} M_{\odot}$ and tracing their individual IHL particles back in time, we classify the origin of each IHL particle at each epoch based on the status of the originating galaxy into three categories: brightest halo galaxy (BHG) formation/merger, satellite galaxy stripping, and pre-processing. Our study reveals that the IHL production through BHG formation/merger is the predominant production channel, contributing over 60\% of the total IHL mass across all redshifts. The second most significant IHL production channel is pre-processing, providing more than 20\% in the final HR5 snapshot. Stripping is negligible at $z>4$ but becomes gradually more important as halos mature at $z<4$. Finally, we verify that IHL production through the disruption of dwarf galaxies and in-situ formation is negligible, contributing less than ~3\% and ~0.5\% to the total IHL production, respectively.