Trends along Hubble Sequence
Roberts & Haynes 1994:
Masses from S0 to Scd roughly constant, then decrease,
and M/L roughly the same (recall these are all
primarily luminous massive galaxies – why?)
H I not significant in ellipticals (< 1 in 10000), but is in
spirals (0.01 to 0.15 from Sa to Sm)
Total surface density decreases, H I surface density
increases
Ellipticals are red, spirals are blue…
H II regions frequency increases monotonically along
the sequence (Kennicutt et al. 1989)
Star formation rates appear key to these relations