Radial Column Density

[brittonsmith]

Issue #1047 on yt.

Originally reported by: Bili Dong (Bitbucket: qobilidop, GitHub: qobilidop)

Is anyone working on porting the radial column density analysis module from yt-2.x to yt-3.x? This functionality is exactly what I need for my current research. I'd like to do the work if no one else is already working on it.

[qobilidop]

Ha, I almost forget about this.

The original difficulty to reimplement the functionality is the license incompatibility with healpy which is copyleft. Now there seems to be an alternative implementation in Astropy. If that's true, we'll be able to add this functionality without license conflict.

[qobilidop]

I have some idea about where to go next for this that I want to jot down here for future reference.

I think the radial column density functionality could be generalized to be another plot window of spherical projection. Basically, this could have an interface like:

yt.SphericalProjectionPlot(ds, fields, center, radius, projection_method, field_method)

The projection_method and field_method could be confusing. I should come up with a better name. The projection_methods are HEALPix, Molleweide, and such. The field_methods are integrate, sum and such. There would be a way to specify weight field and many other things as in yt.ProjectionPlot.

What needs to be done next is to figure out the best place of implementing this, and figure out an efficient implementation. The handling of angular coordinates is very different from cartesian coordinates, which might be a difficulty in the implementation.

[qobilidop]

Regarding the license issue, a BSD-licensed HEALPix for Astropy exists to solve it. See http://astropy-healpix.readthedocs.io/en/latest/about.html.