[yt-users] Absorption Spectrum from Gadget snapshot problem

[Cameron Hummels]

Hi Jared,


>
> I have two questions. First: When calling make_light_ray and passing it
> fields, do I need to pass it H_number_density? Second: Does yt read in
> those fields from the gadget snapshot, or does it calculate them from the
> data in the snapshot (for example, a standard gadget snapshot does not
> write the temperature, but rather the internal energy)?  Thanks!
>


When you run sp.add_line(), you're trying to add a line associated with a
field, in this case, you're associating it with the "H_number_density"
field.  AbsorptionSpectrum expects that field to be present in the light
ray (in this case lr.h5) when you run make_spectrum().  The
"H_number_density" field is a grid-celled neutral hydrogen number density,
which is present in some simulation outputs, however, I do not know if it
is automatically populated for the custom gadget dataset on which you're
running.  Do you trace the neutral hydrogen in your gadget simulation?  If
so, does it spit out to a particle field that you can then deposit into a
grid-based field?  Or were you looking to approximate the HI number density
in yt  by making some assumptions based on the density, temperature,
radiation field, etc.?

Cameron
-- 
Cameron Hummels
NSF Postdoctoral Fellow
Department of Astronomy
California Institute of Technology
http://chummels.org
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