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alm2cl*

This routine computes the auto (or cross) power spectra of a one (or two) sets of spherical harmonics coefficients a_lm. $C_{12}(l) = \sum_{m=-l}^{l} a_{1,lm} a_{2,lm}^* / (2 l+1)$

Location in HEALPix directory tree: src/f90/mod/alm_tools.f90

FORMAT

call alm2cl*( nlmax, nmmax, alm1, [alm2,] cl )

ARGUMENTS

name & dimensionality	kind	in/out	description

nlmax	I4B	IN	the maximum l value used for the a_lm.
nmmax	I4B	IN	the maximum m value used for the a_lm.
alm1(1:p, 0:nlmax, 0:nmmax)	SPC/ DPC	IN	First set of a_lm values. p is 3 or 1 depending on wether polarisation is included or not. In the former case, the first index runs from 1 to 3 corresponding to (T,E,B).
alm2(1:p, 0:nlmax, 0:nmmax) (OPTIONAL)	SPC/ DPC	IN	Second set of a_lm values.
cl(0:nlmax,1:d)	SP/ DP	OUT	resulting auto or cross power spectra. If both `alm1` and `alm2` are present, `cl` will be their cross power spectrum. If only `alm1` is present, `cl` will be its power spectrum. If d=1, only the temperature spectrum C_l^T will be output. If d=4 and p=3, the output will be C_l^T, C_l^E, C_l^B, C_l^{T x E}, and if $d\geq 6$ and p=3, C_l^{T x B} C_l^{E x B} will also be output.

EXAMPLE:

lmax = 128 ; mmax = lmax call alm2cl(lmax, mmax, alm1, cl_auto) call alm2cl(lmax, mmax, alm1, alm2, cl_cross)

cl_auto will contain the (auto) power spectrum of the a_lm coefficients alm1 up to l= 128, while cl_cross will be the cross power spectra of the two sets of a_lm coefficients alm1 and alm2.

MODULES & ROUTINES

This section lists the modules and routines used by alm2cl*.

none

RELATED ROUTINES

This section lists the routines related to alm2cl*

map2alm: routine extracting the a_lm coefficients from a HEALPix map
create_alm: routine to generate randomly distributed a_lm coefficients according to a given power spectrum

Eric Hivon 2010-06-18

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