Yes, that actually makes sense: with the galaxy full of dark matter and gravity less dominating out towards the rim, the dark matter might act as a coagulating agent, turning the galaxy into a (moderately) rigid body.

Signatures? We don''t need no steenking signatures!

Why dont you try a simple little trick. Amke several line segments, like 6 per arm, and just bend them(you could just tune this manuallly, or use math). Make several, like four coming off the center. The segments will look close to a curve. The close the segment is to the center, the more stars it will attract. After you have plotted all of the stars, the variation and randomness of their positions will look like a curve. Or you could calculate the starts like normal. Based on their distance from the center, make them randomly, and exponentialy lower on the screen. The farther away, the lower on the screen. As long as the drop is exponential, it will look like its curving.But on the the vertical axises, you will have to move the stars horizontally