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 Post subject: galprop gas files
PostPosted: Thu May 24, 2007 6:27 am 
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Joined: Tue Feb 20, 2007 1:10 am
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Location: Padova
Which quantity is described in the input file rbands_co4.fits? Is it the number density of hydrogen MOLECULES or the number density of PROTONS in form of molecules?


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 Post subject: rbands co
PostPosted: Fri May 25, 2007 12:14 am 
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Joined: Wed May 17, 2006 7:02 am
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Location: MPE Garching
it's the integrated Tco dv, in units of K km s-1
which has to be converted to molecular hydrogen
column density using the famous Xco factor (e.g. as given in the galdef file).

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Andy Strong, MPE


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 Post subject: galprop gas files
PostPosted: Fri May 25, 2007 12:36 am 
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Location: Padova
I found some misleading information, both in the file header, where you wrote as unit cm^-2, and in the GALPROP v.50 manual (September 6, 2006), where (page 4 bottom) you can read "the H2 gas number density is defined in the form of table ... and the conversion factor is taken as X= ..."


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 Post subject: H2 and rbands
PostPosted: Fri May 25, 2007 12:58 am 
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Location: MPE Garching
there are two things:
1 the galprop internally modelled H_2 which is indeed as described in the manual on page 4, using a fixed Xco=1.9E20. This is used for cosmic-ray propagation but not for gamma-rays

2 the Wco rings in rbands, which are used to compute the gamma-rays.
You are apparently right about the error in the header, I informed Seth Digel !


Clearly 1 & 2 are not consistent: we know this and are working on a new version where they will be consistent. However the effect is not great.
But consistency is very desirable of course.

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Andy Strong, MPE


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PostPosted: Sat May 26, 2007 10:30 pm 
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Location: SLAC
Luigi is correct that the units are incorrectly stated in the header of rbands_co4.fits. They are K km s^-1, as Andy says. It was just a mistake to list the units as '10E20 cm-2'. This came about because I used the same BUNIT string for the H I rings (rbands_hi7.fits).

10E20 cm-2 now looks ambiguous (or wrong) to me for the H I rings. I meant 10^20 cm^-2. I'll fix the headers of both files in their next update.

Thanks, Luigi, for pointing out the error.

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Seth Digel


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