by flash » Fri Jan 21, 2011 5:20 pm
Chris, thanks for the detailed explanation.
All this has got me thinking about the angular momentum of galaxies. Given your reponse that in a spiral galaxy all the stars have "virtually the same angular velocity", I wonder if anyone has plotted the angular momentum of galaxies (due to the stars, not necessarily considering the dark matter halo)? I believe that the angular momentum of spherical galaxies must be significantly less than spiral galaxies, if only because the stars in them move more randomly, subject to frequent perturbations from each other, and if the stars shared the same or similar angular momentum, wouldn't they evolve into a disk-shaped galaxy? So how does the angular monentum of galaxies vary (between galaxies)? What would the shape be of a plot of galactic angular momentum vs galactic mass? How about vs galactic diameter? vs galaxy type? What about elliptical galaxies angular momentum? Would elliptical galaxies have greater angular momentum than a similar sized spherical galaxy, but smaller than a similar sized spiral galaxy?
On a separate note, are the angular momentum vectors of galaxies aligned at all with each other, (perhaps just locally), or are they random as the orientation of their disks appear?
Thanks again.
Chris, thanks for the detailed explanation.
All this has got me thinking about the angular momentum of galaxies. Given your reponse that in a spiral galaxy all the stars have "virtually the same angular velocity", I wonder if anyone has plotted the angular momentum of galaxies (due to the stars, not necessarily considering the dark matter halo)? I believe that the angular momentum of spherical galaxies must be significantly less than spiral galaxies, if only because the stars in them move more randomly, subject to frequent perturbations from each other, and if the stars shared the same or similar angular momentum, wouldn't they evolve into a disk-shaped galaxy? So how does the angular monentum of galaxies vary (between galaxies)? What would the shape be of a plot of galactic angular momentum vs galactic mass? How about vs galactic diameter? vs galaxy type? What about elliptical galaxies angular momentum? Would elliptical galaxies have greater angular momentum than a similar sized spherical galaxy, but smaller than a similar sized spiral galaxy?
On a separate note, are the angular momentum vectors of galaxies aligned at all with each other, (perhaps just locally), or are they random as the orientation of their disks appear?
Thanks again.