The faint light in groups and clusters of galaxies
  The diffuse light that spreads through groups and clusters of galaxies is
made of free-floating stars not bound to any galaxy. This is known as the
intracluster light (ICL) and holds important clues for understanding the
evolution of these large structures. The study of this light has gained
traction in the past 20 years thanks to technological and data processing
advances that have permitted us to reach unprecedented observational depths.
This progress has led to ground-breaking results in the field, such as
pinpointing the origin of the ICL and its potential to map dark matter in
clusters of galaxies. We now enter an era of deep and wide surveys that promise
to uncover the faint Universe as never seen before, adding to our growing
understanding of the properties of the ICL and, consequently, of the formation
of the largest gravitationally bound structures in the Universe. The goal of
this Review is to summarize the most recent results on ICL, synthesizing the
current knowledge in the field and providing a global perspective that may
benefit future ICL studies.
