[yt-dev] Projections of FITS cubes

[John ZuHone]

FWIW, it would make more sense if the units of each slice were Jy/beam/(km/s), because then integrating along that axis would truly be integrating a spectrum, but I've never seen radio people treat it that way. 

On Jul 7, 2014, at 11:50 AM, John ZuHone <jzuhone at gmail.com> wrote:

> Nathan,
> 
> At the moment we've left the units of all of the axes in code_length, which is equivalent to the FITS pixel (except in cases where the z-axis is rescaled, in which case along that axis it is a multiple of the pixel). 
> 
> For these datasets, I actually don't think that projections with a path length (whether in terms of length or velocity) makes a lot of sense--since the units along each slice are Jy/beam and the total projected intensity is in the same units. That's why for this image, when we used it in this notebook:
> 
> http://yt-project.org/docs/dev-3.0/cookbook/fits_radio_cubes.html#radio-cubes
> 
> we specified proj_style="sum" which eliminates the path length and simply sums everything along this axis. 
> 
> Best,
> 
> John
> 
> On Jul 7, 2014, at 11:43 AM, Nathan Goldbaum <nathan12343 at gmail.com> wrote:
> 
>> Hi all,
>> 
>> I think this question is primarily for John ZuHone, but please feel free to jump in.
>> 
>> I'm currently looking at the FITS frontend for my scipy talk.
>> 
>> I just made a projection of the M33 HI data cube we have on the data hub.  The image is here: http://i.imgur.com/kcw98g8.png
>> 
>> I know that we decided to not try to jam WCS axes into the PlotWindow code, instead reserving that for PlotWindowWCS.  I agree with that.
>> 
>> However, I'm confused about the units of the z-axis.  Presumably, the units of the actual observation are km/s.  Did we ever investigate making the units of the z-axis km/s? Is that not possible at the moment due to a restriction that all three axes must have spatial units?
>> 
>> Thanks for your advice,
>> 
>> Nathan
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