I worked on various things relating to big, bright galaxies in the SDSS and other surveys. I also emailed the following to Hans-Walter Rix (MPIA) in preparation for my trip to Heidelberg this summer. It was partly inspired by this post by Rob Knop.
Imagine that spiral arms are created by tidal events which are then "wound up" by differential rotation. Then we can use kinematic information to "unwind" the arms and measure a "time interval" since the last tidal event. Compare this unwinding time to various possible timescales, such as those in star formation histories or in the kinematics of companions and check all simple hypotheses. Now that's an insane project; only the optimistic could embark on that one...!
What would an unwound spiral galaxy look like? My guess would be that it would look something like the cartwheel galaxy.
ReplyDeleteIt shouldn't be to hard to figure out how much time it takes for the arms to wind up after the tidal shock.
S0+shock-> Sa -> Sb -> Sc -> E/S0 ?