[yt-users] different hydrogen densities from different versions of yt

Josh Moloney Joshua.Moloney at Colorado.EDU
Fri Mar 3 13:33:26 PST 2017

In yt-3, the H_number_density field should be the neutral hydrogen number
density (The ionized hydrogen is given in H_p1_number_density). Although I
haven't worked with yt-2.7 recently, it looks like the H_NumberDensity
field there is giving you the overall hydrogen number density. The two
plots you've attached seem consistent with that. A quick way to check this
would be to divide your H_number_density field by H_fraction and see if you
get numbers that match up.
     - Josh

On Fri, Mar 3, 2017 at 1:44 PM, Lauren Corlies <laurennc009 at gmail.com>

> Hello,
> I've been a yt user for a while now but have recently noticed something
> concerning. A few months ago, I made the switch to yt3 and am currently
> using the new yt 3.3.4
> I've been working with recently generated, cosmological zoom in
> simulations and I've generated a basic yt ray object.  When I plot the
> hydrogen number density along the ray, the values that it's generating are
> un-physically low (seen here <http://i.imgur.com/1C1oAVr.png>).
> It's especially concerning because when I use the old yt2 installation:
> Version = 2.7-dev
> Changeset = 1f9ca06815d0
> and generate a yt ray object with the exact same trajectory, the hydrogen
> number density values are much more sensible (seen here
> <http://i.imgur.com/tcDcNd8.png>). The rays in both yt versions have
> mostly the same shape but there are some strong features in the yt2 version
> than in the yt3 one.
> The discrepancy is specifically with this field and not other intrinsic
> fields like temperature or regular density (also attached).
> Am I accessing the field incorrectly and there's a better way to get these
> values with the new version of yt? Or is there something deeper happening?
> The hydrogen number density is particularly important for the ion densities
> and emission that I've been interested in.
> All of the plots and the script <http://paste.yt-project.org/show/7066/>
> to generate them are attached and posted online as described on the docs
> page, tagged with my last name with links included as an attachment.
> Thanks for the help,
> Lauren Corlies
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