About this Research Topic
The Intracluster light (ICL) is an important component in galaxy groups and clusters, made of stars not bound to any galaxy, including the brightest cluster galaxy (BCG). In the last decades, several studies attempted to understand the mechanisms that led to its formation, by looking at its properties such as the amount, colors, metallicity and ages. From the theoretical side, both numerical simulations and semi-analytic models have given a large contribution, by isolating the physical mechanisms responsible for the formation of the ICL, i.e., stellar stripping of satellite galaxies and mergers. Moreover, we now know the importance of the ICL in the context of the dynamical state of the host cluster, and we know that it is possible to make use of it as a visible tracer of the dark matter.
There are still open problems for which the scientific community has not reached a general agreement. In the context of observations, it is not trivial even to define the ICL and separate it from the BCG. The relative contribution of the ICL with respect to the total light in a cluster can indicate the evolutionary state of the cluster itself. The ICL fraction as a function of time, i.e., in clusters at different redshift, not only can show the hierarchical growth of the ICL, but its link with the growth of the BCG, once the growths of the two components are compared. Finally, the possibility of using the ICL as a visible tracer of the dark matter appears to be an extraordinary achievement.
The scope of this Research Topic is to collect both observational and theoretical studies that can focus on the most important properties of the ICL, or BCG+ICL, at different redshifts and in a large halo mass range. Is the ICL in groups different from the ICL in clusters? When and where did the ICL form? Through which mechanisms? Is stellar stripping more important than mergers? What kind of galaxies contribute the most to the formation of the ICL? When BCG and ICL are considered as a whole system, at what distance from the centre the ICL is becoming more important? Is there a universal profile that can be used to describe the ICL distribution?
The above questions are all influent in the context of this Research Topic. To summarize, all contributions that can achieve one or more of the following items are worth being part of this collection:
1) ICL fractions in groups and clusters at different redshifts as tracer of the evolutionary state of the host halo;
2) Colors, metallicity and age of BCG+ICL systems as tracers of the physical mechanism responsible for the ICL formation;
3) BCG+ICL surface brightness profiles to isolate the transition radius where the ICL dominates the distribution;
4) Do BCGs and ICL coevolve?
5) Can we link the ICL distribution to the dark matter one? Can the ICL trace the dark matter distribution?
Keywords: Galaxy Clusters, Galaxy Formation, Galaxy Evolution
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