Created notebook on plotting galaxies

[ojustino]

An adaptation of Mark SubbaRao's notebook on plotting galaxies through Cosmicflows-2.

[pkgw]

Is this blocked on any bugs or missing features in pywwt?

One thing I noticed is that I don't think the PV color mapping is working right. The plt.cm.magma() function either takes floats, in which case they should range between 0.0 and 1.0, or integers, in which case they should range between 0 and 255. Currently the peculiar velocities are rounded to integers, but they range from large negative to large positive values, so a lot of the color mappings clip. The inputs should be normalized first. The first thing I'd try is finding the largest absolute value, M = max(np.abs(cosmic_flows['PV'])), and then applying a linear transformation such that -M maps to 0 and +M maps to 1.0.

[ojustino]

I don't think this is blocked on anything missing in pywwt.

Thanks for the catch on plt.cm.magma. I'll apply the transformation and also test to see if galactic mode is working the way I expect given issue 184 in the pywwt repo.

[ojustino]

*If things are OK once that's done, please let me know before you merge so I can remove my comments to self.