[yt-users] comoving distance a_box

[Nick Gnedin]

Britton,

In the simulations with the non-zero DC mode there are two scale factors 
to consider, a_uni (global scale factor of the universe) and a_box (the 
scale factor of the simulated region). YT recognizes this when reading 
ART data, but appears to use a wrong scale factor in computing comoving 
units.

n


On 10/13/2017 2:44 PM, Britton Smith wrote:
> Hi Huanqing,
> 
> I am a bit unclear on what the problem is.  I think it is correct that 
> the conversion between proper and comoving uses the expansion factor.  
> I'm not sure what abox is.  Can you elaborate on that?
> 
> Britton
> 
> On Thu, Oct 12, 2017 at 4:27 PM, Huanqing <hqchen at oddjob.uchicago.edu 
> <mailto:hqchen at oddjob.uchicago.edu>> wrote:
> 
>     Hi all,
> 
>     I’m using yt to generate halo catalog. However, when I check the
>     halos created by HaloCatalog function, I found the corresponding
>     comoving unit uses the expansion factor of the universe rather than
>     a_box.
> 
>     For example, My boxsize is 20cMpc/h, but if I use
>     .in_units(‘Mpccm/h’), the halos are offset by some amount (see
>     attached). I wonder if this is a bug in converting physical unit to
>     comoving unit?
> 
>     Thanks,
>     Huanqing
> 
> 
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