Tidal streams of intracluster light

Abstract

Using N-body simulations, we have modeled the production and evolution of substructures in the intracluster light (ICL) of a simulated galaxy cluster. We use a density-based definition of ICL, where ICL consists of luminous particles which are at low densities, to identify ICL particles and track their evolution. We have implemented a friends-of-friends-type clustering algorithm which finds groups of particles correlated in both position and velocity space to identify substructures in the ICL, hereafter referred to as "streams." We find that 40% of the cluster's ICL is generated in the form of these massive (M ≥ 7.0 × 108 M 2), dynamically cold streams. The fraction of the ICL generated in streams is greater early in the cluster's evolution, when galaxies are interacting in the group environment, than later in its evolution when the massive cluster potential has been assembled. The production of streams requires the strong tidal fields associated with close interactions between pairs of galaxies, and is usually associated with merging pairs of galaxies, or fast, close encounters with the cluster's central galaxy. Once streams are formed, they begin to decay as they are disrupted by the tidal field of the cluster. We find that streams have decay timescales which are 1.5 times their dynamical time in the cluster. © 2009. The American Astronomical Society. All rights reserved.