On Friday, April 3, 2015 at 5:54:07 AM UTC-4, Jan Panteltje wrote:

OK,
they say a picture is a thousand words:
http://photojournal.jpl.nasa.gov/jpeg/PIA16613.jpg
http://www.space.com/25584-milky-way...iral-arms.html


Note the bar like structure at the center,
and how star formation is most intense there,
and how it 'fades out' at the end of the spiral arms.
Clearly the bar like structure is rotating.

I'm not sure why you picked a disturbed galaxy that has huge tidal tails, but you did. That is not a typical example of a spiral.

I don't believe that the galactic dynamics of spiral formation and bar formation are completely settled, but they do not require stars being "spit out" by a central black hole. Rather, it is more like a traveling wave pattern, and/or standing wave.

CM