[Yt-dev] halo profiler recentering bug-thing

[Eric Hallman]

This problem has been around for a while, with or without yt.  In the  
radial profiles I think it's obvious that two problems arise that  
you're seeing here.  First is what was described earlier in the  
thread, which is that unless you include the position of the zone  
centers in the range of the radial criteria it gives NaNs.  We talked  
in the past about taking fractional zone values etc as a fix (pre-yt).  
The second is if the inner bins are too narrow they sometimes exclude  
either all, or all but a few zone centers, which makes the profiles  
choppy.

What observers do is bin the profiles based on the photon statistics  
(in the case of the X-ray), which can be approximated by some  
logarithmic binning typically.  This can be calculated simply given  
the average surface brightness profiles.  However, that isn't exactly  
analogous, as all objects are different as far as their surface  
brightness profiles.

I'm also surprised about britton's fix (that it didn't work I mean).   
It seems to me that should work, unless the spherical shells for  
averaging outside that are just too narrow.

Eric
On Apr 19, 2011, at 10:44 PM, Britton Smith wrote:

> Hi everyone,
>
> Britton here.  I tried changing the value of r_min to 3 x the  
> smallest dx and it didn't seem to fix the problem, which I am  
> somewhat confused by.  However, I think setting end_collect to True  
> is just fine.  I'm for it.
>
> Britton
>
> On Tue, Apr 19, 2011 at 3:43 PM, Stephen Skory <s at skory.us> wrote:
> Matt,
>
> > Or you could turn on end_collect, which should be 100% fine for a
> > sphere whose limits are defined as some really, really small radius
> > and the radius of that sphere.  end_collect only becomes a problem
> > when your object is not pre-constraining your values.
>
> I think that this is a good solution because it may better match what
> observers do. Britton, I think that this should be on by default, what
> do you think? Otherwise, it should be a parameter to the halo
> profiler.
>
> --
> Stephen Skory
> s at skory.us
> http://stephenskory.com/
> 510.621.3687 (google voice)
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Eric Hallman
Google Voice: (774) 469-0278
hallman13 at gmail.com




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