I finished and submitted my Marseille review. In the end, this is what I wrote about morphology–density:
In Figure 5 I show the variation of concentration (a measure of bulge/total ratio and therefore a morphology surrogate [citations]) on environment (clustocentric distance, a high-precision but variable-scale environment measure), in narrow color slices. In Figure 6 I show the variation of color on environment in narrow concentration slices. These Figures look very different: Color depends on environment independently of morphology, morphology does not independently of color. Of course I am over-stating the result by calling thismorphology; take it as you wish, but it is clear that color and concentration are not on an equal footing when we ask what they can tell us about environment.
In current thinking about the reasons for the morphology–density relation (things like ram-pressure stripping, mergers, late accretion, tidal perturbations), these results are very difficult to understand. What physical processes cantellgalaxy star-formation rates about their environments andtellmorphologies to keep track of star-formation rates but not do much to the morphologies independently? I think the conclusion has to be that the processes that set morphology (or, really, concentraion or bulge/total ratio) are somehow internal to the galaxies.