Here is an extremely deep image of the Virgo Cluster of Galaxies showing the extremely faint inter-galaxy (intracluster) light between the member galaxies.
It was taken with the Burrell Schmidt by Chris Mihos and Paul Harding of CWRU.
Here is another version of the same image, at higher contrast. It was also made by these two professional astronomers.
The depth of this image is to a V-band surface brightness of 28.5 magnitude per square arcsec.
Strange to think that an appreciable fraction of the total number of stars in the Virgo Cluster of Galaxies is located
in between its galaxies.
However, as Obi Wan Kenobi said, "these are the truths that we must cling to".
The intracluster (inter-galaxy) light can contribute 10-20 Percent of the total light in certain clusters of galaxies!
See:
http://astroweb.case.edu/hos/Virgo
for more about how this image was made.
The associated scientific paper is:
Mihos et el., (2005), ApJ,
631, 41
In the scientific literature, you will find that the Intracluster Light is shortened to "ICL"
(Yet another obscure acronym!)