[yt-users] Best way to load in halos?

[Stephen Skory]

Christine,

> A suggestion, if it isn't too much trouble.  Could you add a column for
> mass?

Actually, just as I sent my last reply I thought a bit harder, and I
realized that this raises a prickly issue. Let me explain.

When you run a halo finder in yt, and save your results with .dump(),
you can use LoadHaloes() to recover carbon-copies of what you had
before. Any operation you ran on the halos before .dump() will give
you the same answer with them loaded later on. This is because with
.dump() everything that makes up the halos, in particular the full
particle assignments, is saved to disk.

However, with this text loading method, we don't know anything about
what particles are in the halo when the halo finder was run. This
means that all we can do (and it's what I'm doing in this new method)
is simply define the halo as a sphere centered on a point. If I ask
for particle information from this halo, it will use the sphere.
Typically, halos found by halo finders are not spheres.

Now, if we read in mass from a text file as you suggest, what mass is
this? If it's the mass of the particles as the halo finder you used
calculated, what does that mean in yt? It can't reproduce this mass on
its own, and this mass doesn't correspond to anything yt knows about,
namely, a nondescript sphere.

I'll have to think about this some more, but the TL;DR is that
specifying a mass like this from a text file introduces some
ambiguity.

I'm still open to other column suggestions.

-- 
Stephen Skory
s at skory.us
http://stephenskory.com/
510.621.3687 (google voice)