Extrapolate websky CIB emission below 18.7GHz

[zonca]

Websky provides CIB templates between 18.7 GHz and 1080 GHz.
Upcoming low frequency channels in Simons Observatory and CMB-S4 extend their bandpass below 18.7 GHz.

Can the websky team provide maps down to 1 GHz? If this is not doable, can we do a rough extrapolation, just scaling properly the 18.7 GHz map?

[giuspugl]

Hello @zonca ,
sorry for my late reply! i believe that for the model employed in websky CIB it is fine to just extrapolate and rescale it down to the lowest freq. If you agree can provide you the parameters for the rescaling .

[zonca]

yes please @giuspugl

[giuspugl]

you can use Td from : https://github.com/WebSky-CITA/XGPaint.jl/blob/9ddd9512b0936ad57422dcedd965ea4f7b7cc60b/src/cib.jl#L17
and Bd value from https://github.com/WebSky-CITA/XGPaint.jl/blob/9ddd9512b0936ad57422dcedd965ea4f7b7cc60b/src/cib.jl#L18
i'd stress that this rescaling does not take into account the redshift dependence of each star forming galaxy, but I think it is a quick and dirty compromise given the fact that we are interested in a very low freq. maps.

[zonca]

ok, can you provide a notebook that does this?
The notebook can get the necessary maps directly from NERSC:

!wget https://portal.nersc.gov/cfs/cmb/pysm-data/websky/0.4/cib/cib_0018.7.fits