Speed of light should be from scipy.constants

[londumas]

The speed of light should be 299792458.0 everywhere, there are no reason to make an approximation. Also it can produce such shift of the correlation function, see issue #41.
The best way is to use from scipy.constants import speed_of_light, in order not to hard code it nor to cast it to smaller precision.
Doing simple grep, I get:

<HOME>/Programs/igmhub/LyaCoLoRe> grep '2.99' -ri * --include \*.py
py/lya_mock_functions.py:        c_kms = 2.998e5

This ticket is linked to this more general one: desihub/desisim#477

[londumas]

It seems to explain part of the shift of #41 dv = 7.54 km/s.

c = 2.998e5
from scipy.constants import speed_of_light
speed_of_light /= 1000.
dv = c-speed_of_light
print(dv)

[londumas]

@jfarr03, There might be other places where the speed of light is defined that I have not found.

[jfarr03]

@londumas the speed of light isn't used anywhere explicitly in LyaCoLoRe's scripts to produce the mocks - the instance you found isn't used anywhere other than very old examples. I'll correct it nonetheless but it won't be affecting the realisations.

It is almost certainly used in CoLoRe somewhere, though, so I'll have to check exactly what is used there.

[londumas]

Ok. Could you send the link to the CoLoRe code ?

[londumas]

@jfarr03, is that the one: https://github.com/damonge/CoLoRe?

[londumas]

Doing some greps the only thing I found that looks like the speed of light is the following, that seems ok, but has strange units.
https://github.com/damonge/CoLoRe/blob/43abfec9230bd6f37ec3498d499cc61195cb1e5d/src/cosmo_mad.h#L35

[jfarr03]

Yes sorry that's the right link - it seems like it's ok but you're right, the units are odd!

[londumas]

I just open a ticket there: damonge/CoLoRe#38 to better understand what it is.

[londumas]

@jfarr03, could you fix the following line, and then we can close:
igmhub/LyaCoLoRe/py/lya_mock_functions.py: c_kms = 2.998e5
I know it is not used, but let's fix that so it does not show up.
Thanks for the help.

[jfarr03]

@londumas fixed in commit 4ed3ebf

[londumas]

@jfarr03, thanks