Interesting thing, this...
Why should the 'baby' be 'overweight'?
Perhaps a time will come (or - in this case - has already gone by) when astronomers will consider the possibility that they might just be looking at a couple of galaxies stacked extremely close - a 'twin', so to say...
From a distance, they will give the appearance of a single 'heavy' galaxy. Spectrographs and red-shift analyses also won't show the difference as they are just too close...
There are still far too many unknowns 'out there'...
Why are galaxies formed when stars begin to 'cluster' together? Why do stars start clustering? And why do they stop from each other at a distance? Do they get embedded in a dark-matter matrix?
It is impossible to discount this 'dark matter'. This is the thing that 'balances' the bright matter in the universe. There isn't emptiness between stars/galaxies. There is a clearly tangible fabric of dark matter.
If one starts studying the various nebulae, one finds strands, layers or trails of dark matter drifting through the nebulae, thereby giving them strangely familiar shapes - so that astronomers can name those objects accordingly...
Vivek, one more teasing post from me
Having given you something to think about, main chalaa....