That's quite a polar ring!

Well, sort of…

Looks like it could be a cool stellar stream from a past minor merger with the main galaxy

Which is, I believe, what causes polar rings?

I believe that polar rings and stellar streams are caused by the same origin (mergers), but i’m not sure of the exact conditions to form a polar ring. I think it has something to do with the rotation of the galaxy, but I may be corrected