Add option to simulate CMB lensing

[andreufont]

@Laura-Casas generated a CMB lensing kapp map recycling the weak lensing functionality setting z_out= [3.8], but this is not quite what we want.

As pointed out by @carlessanchezalonso, what we should do is integrate to z_out but use a lensing kernel that has the source at z=1100, not at z_out.

Pinging here also @dljarque who is validating the CMB lensing maps simulated by Laura.

@damonge - this seems like a trivial thing to fix, but I wonder whether you have a preferred way of fixing it. We could add an extra option to the kappa section, something like z_source or z_cmb to make it clear that should only be used for CMB lensing. What do you think?

[damonge]

Yep, happy to implement this (and it should have been there from the beginning TBH).
I guess if you want the resulting map to have the correct auto-correlation you'll need to add Gaussian noise to fill the kernel up to z=1100

[damonge]

@andreufont , turns out this was almost done in the original code anyway. It's implemented in #76 - take a look if you can, and let me know if you were thinking of something else.

[andreufont]

Awesome, we'll take a look at it and try to run a new box from that branch.

Just to be clear, the user just needs to:

• specify z_out=1100 (or whatever z_out corresponds to the last scattering surface in the chosen cosmology)
• no need to specify z_max, this is automatically computed by CoLoRe given the box size and the cosmology

Correct?

[damonge]

There's a z_max in the param file (e.g.

CoLoRe/param_example.cfg

Line 14 in 7f2eb68

z_max= 0.450

) which defines the size of the box.

But yes, that's right! Let me know if it works.