Mike,
I have been having another look at your image of the IC 4765 galaxy cluster. Small galaxies here, but they are nicely seen in your image.
This is, for me, one of your very most interesting images, as this cluster is very very rarely imaged by anybody, and there is hardly anything known about it, even by the "pros".
(in fact, the galaxies in Pavo are the least known in the sky, judging from the tiny number of scientific papers written about them)
The halo of the giant dominant elliptical galaxy is not symmetrical,
if I am correct in my interpretation of your image....
it seems to stretch outwards a lot further along the upper side of the major axis of this galaxy.
I don't know whether the extremely faint luminous background which I seem to see extending away from this galaxy is the intracluster (inter-galaxy) light or whether it more properly belongs to the halo of this galaxy.
There are a number of cases in the literature where the exceedingly faint luminous halo of a big elliptical in the middle of a galaxy cluster essentially merges, at some radius, with the intracluster light;
so the distinction may be somewhat academic.
( a good example of this is M86.....if you measure the total magnitude of M86 to successively greater radii, the total brightness of this galaxy just keeps on increasing.....there is no radius at which the magnitude stops getting brighter!!!)
[ The intracluster light in galaxy clusters is not unusual in terms of its composition, in that its light just comes from plain ordinary stars....but the stars
belong to the cluster of galaxies rather than to any individual galaxy]
cheers,
Robert
I don't suppose that these giant Elliptical galaxies are the most exciting looking galaxies in the sky, but they are often the most luminous galaxies in the universe; some examples get two magnitudes more luminous than even the most luminous spiral galaxy.
They do have sort of subtle "layered" structure, sort of "onion-like", as has been very evident to all of us who have followed your NGC 5128 imaging project, in that the shape and position angle of one of these galaxies can change two or more times, depending upon the radius to which the galaxy image is displayed.
One of my favourite examples is NGC 6876, which has a centralmost or nuclear feature, surrounded by an oval distribution light, surrounded by a spherical distribution of light, surrounded by a probably-off- centre very-extended distribution of light. Some hint of this structure in these isophotes:
Attachment 152708