Stellar Steams in Intergalactic Space
It's easy to think that all stars exist neatly with a galaxy island, but the above montage shows a number of nearby large galaxies, and inverted to show the streams of stars that often stretch out 100's thousands of light years.
Cosmologists enjoy modelling the universe, and understanding how halo's and these star streams work help them create a better understanding and model of how galaxies evolve.
For example, I suspect you've not seen the above image representing our Milky Way, imagine if our Sun had been located in one of these streams, literally looking back at our own Milky Way, and a much darker sky at night.
Many of these steams are related to dwarf galaxies interacting and eventually being consumed by the main galaxy, it is the eventual fait of the Magellanic clouds, but has happened a number of times in the Milky Way's history.
Ultimately merger between larger galaxies ends up throwing out huge streams, unwound arms of galaxies that are stripped off as the mass of another galaxy beings to take hold, only to them move away leaving the arms outstretched, some of which may never return to the newly merged galaxy, while others eventually.
