Amazing image and thanks for the write up! Really interesting.
In the paper you attached there is a reference to NGC 253 (the silver coin galaxy) having an extension to one side of the galaxy. I'm researching this and can't find what they're referring to
(Or probably its right there and I can't understand it
)
The silver coin galaxy in all its glory:
https://apod.nasa.gov/apod/ap200414.html