CAMB Sources: Weak Lensing Window Function

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Danielle Leonard
Posts: 3
Joined: March 25 2014
Affiliation: University of Oxford

CAMB Sources: Weak Lensing Window Function

Post by Danielle Leonard » March 25 2014

Hello all,

I am trying to understand the exact expression for the window function used in CAMB Sources to calculate the convergence power spectrum for weak lensing. The subroutine output contains the following expression for a weak lensing source:

Code: Select all

sources(3+w_ix) =-2*phi*W%win_lens(j)
where w_ix runs over the number of redshift windows for lensing.

I am wondering if anyone knows the expression for W%win_lens(j)? I understand that it is calculated from awin_lens in the subroutine inithermo, but I am having trouble understanding this calculation. It doesn't seem to me as though it produces either a simple Gaussian in redshift or the standard lensing kernel g.

Thanks very much for any help!

Danielle Leonard

Antony Lewis
Posts: 1941
Joined: September 23 2004
Affiliation: University of Sussex
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Re: CAMB Sources: Weak Lensing Window Function

Post by Antony Lewis » March 26 2014

The source function is derieved from the the standard geometric factor for weak lensing along with the source distribution function, [tex]W(z)[/tex], that you can change. So win_lens is something like
[tex]
\int_0^\eta \frac{\chi'-\chi}{\chi\chi'}W(\eta')d\eta'
[/tex]
where [tex]\chi'=\eta_0-\eta'[/tex] (and similar for [tex]\chi[/tex]) and [tex]\eta[/tex] is the conformal time. Usually you only need to change the underlying window function count_obs_window_z in modules.f90.

Danielle Leonard
Posts: 3
Joined: March 25 2014
Affiliation: University of Oxford

CAMB Sources: Weak Lensing Window Function

Post by Danielle Leonard » April 01 2014

Thanks very much for your reply Dr. Lewis!

I was wondering also whether you or anyone else might be able to confirm whether, in this non-CMB weak lensing case, the autocorrelation [tex]C_l[/tex] s output in either the scalcovCls or the scalCls file represent [tex]C_l^{\phi \phi}[/tex] (for the lensing potential) or [tex]C_l^{\kappa \kappa}[/tex] (for the convergence)?

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