projecting chemical abundances & projecting to physical units with colorbar

[agurvich]

as pressing p but multiplying the "mass" of the particle by a field-- say, the H_2 abundance (so we can plot H_2 column density).

on a related note, if we are able to project an arbitrary field then it should be almost trivial to project the mass in appropriate units such that what we get at the end is a proper column density

[agurvich]

projecting to physical units is done now. we can successfully project to # of particles overlapping pixel. though it seems like it might be saturating at 10 particles? at least in the gaia dataset that happened. won't close the issue but we should keep an eye on this