Added more surface density and surface brightness plots

[sylviaploeckinger]

Added the following plots to the pipeline:

• Combined surface densities:
  - azimuthally averaged H2 / HI vs H2 + HI, color coded by metallicity
  - azimuthally averaged H2 / HI vs H2 + HI, color coded by stellar surface density
  - grid averaged H2 / HI vs H2 + HI
  - grid averaged molecular gas vs. stellar surface density
  - grid averaged star formation rate surface density vs. molecular surface density
  - grid averaged star formation rate surface density vs. stellar surface density

• Gallery of individual galaxies for a quick overview including:
  - face-on / edge-on view of stars (unattenuated gri composite image), HI, and H2; plus the individual azimuthally averaged H2/HI vs. H2 + HI surface densities, color coded by gas metallicity

[Fonotec]

Hi Sylvia, one comment Gas particles maps and gas component maps are not consistent. They seem to be orientated differently? Maybe they are flipped or rotated compared to each other? The same for the star maps.

[sylviaploeckinger]

Hi Folkert, I found that very often the angular momentum vectors of all stars in the halo from VR does not align the galaxies very well. For the larger boxes many galaxies that looked like obvious disk galaxies were not properly rotated. I was looking at the scale heights and especially for those it is very important that the edge-on projection is really edge-on but also for the surface densities we want the galaxies to be really face-on. Because of this, I do not use the VR angular momentum values but calculate it separately from a fraction of the stars within a 30 kpc aperture. I found the best results when skipping the most central (bulge) and the outermost (stellar halo) star particles. I think the original maps and particle scatter plots use the VR angular momentum, that's why they are different.
I'm sure there is a better way of orienting the galaxies and it would be great if this was already calculated within VR. I was looking for stellar (or gas) angular momentum vectors within apertures but they are not there by default.

Edit: If you are referring to the example I have posted on Slack, I think I misunderstood your comment. It can still happen that the projection in the new (swiftsimio) and the old (pysphviewer) maps are different because of the above reason, but I just noticed that also for the original plots, the gas surface density maps and the gas particle plots do not match. I am pretty sure this is the weird python thing where imshow inverts the axis by default compared to a scatter plot. This can be fixed with adding origin = 'lower' to the imshow call.

[correac]

Great work Sylvia!