Formation channels of the diffuse lights in the groups and clusters over time

TL;DR

This study uses cosmological simulations to investigate the origins and evolution of diffuse intragroup and intracluster light from redshift 1.5 to the present, highlighting the roles of progenitor mass, dynamical state, and merging processes.

Contribution

It introduces a novel simulation approach with galaxy replacement to trace the formation channels of diffuse light in groups and clusters over cosmic time.

Findings

Diffuse light mainly originates from progenitors with stellar mass 10^10 to 10^11 solar masses.

Stripping of satellite galaxies is the primary formation mechanism for diffuse light.

Diffuse light fraction decreases with redshift but is already significant at z=1.5.

Abstract

We explore the formation of the intragroup light (IGL) and intracluster light (ICL), representing diffuse lights within groups and clusters, since $z=1.5$. For this, we perform multi-resolution cosmological N-body simulations using the ``galaxy replacement technique" (GRT) and identify the progenitors in which the diffuse light stars existed when they fell into the groups or clusters. Our findings reveal that typical progenitors contributing to diffuse lights enter the host halo with the massive galaxies containing a stellar mass of $10 < \log M_{\rm{gal}}~[M_{\odot}]< 11$, regardless of the mass or dynamical state of the host halos at $z=0$. In cases where the host halos are dynamically unrelaxed or more massive, diffuse lights from massive progenitors with $\log M_{\rm{gal}}~[M_{\odot}]> 11$ are more prominent, with over half of them already pre-processed before entering the host halo. Additionally, we find that the main formation mechanism of diffuse lights is the stripping process of satellites, and a substantial fraction ($40-45\%$) of diffuse light stars is linked to the merger tree of the BCG. Remarkably, all trends persist for groups and clusters at higher redshifts. The fraction of diffuse lights in the host halos with a similar mass decreases as the redshift increases, but they are already substantial at $z=1.5$ ($\sim10\%$). However, it's crucial to acknowledge that detection limits related to the observable radius and faint-end surface brightness may obscure numerous diffuse light stars and even alter the main formation channel of diffuse lights.