This routine modifies scalar (and tensor) alm by multiplying them by a beam window function described by a FWHM (in the case of a gaussian beam) or read from an external file (in the more general case of a circular beam) $a_{lm}
\longrightarrow a_{lm} b(l) $ . It can also be used to multiply the alm by an arbitray function of l.

Location in HEALPix directory tree: src/f90/mod/alm_tools.F90 


call alter_alm*( nsmax, nlmax, nmmax, fwhm_arcmin, alm_TGC[, beam_file, window] )


name & dimensionality kind in/out description
nsmax I4B IN ${N_{\rm side}}$ resolution parameter of the map associated with the alm considered. Currently has no effect on the routine.
nlmax I4B IN maximum l value for the alm.
nmmax I4B IN maximum m value for the alm.
fwhm_arcmin SP/ DP IN fwhm size of the gaussian beam in arcminutes.
alm_TGC(1:p,0:nlmax,0:nmmax) SPC/ DPC INOUT complex alm values to be altered. The first index here runs from 1:1 for temperature only, and 1:3 for polarisation. In the latter case, 1=T, 2=E, 3=B.
beam_file(LEN=filenamelen) (OPTIONAL) CHR IN name of the file containing the (non necessarily gaussian) window function Bl of a circular beam. If present, it will override the argument fwhm_arcmin.
window(0:nlw,1:d) (OPTIONAL) SP/ DP IN arbitrary window by which to multiply the alm. If present, it overrides both fwhm_arcmin and beam_file. If nlw < nlmax, the alm with $l\in \{$nlw+1,nlmax} are set to 0, and a warning is issued. If d<p the window for temperature is replicated for polarisation.


call alter_alm(64, 128, 128, 1, 5.0, alm_TGC)
Alters scalar and tensor alm of a map with ${N_{\rm side}}=64$, $l_{\rm
max}=m_{\rm max} = 128$ by multiplying them by the beam window function of a gaussian beam with FWHM = 5 arcmin.


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

module, containing:
routine to generate beam window function
routine to generate pixel window function


This section lists the routines related to alter_alm*

Routine to create alm coefficients.
Routine to rotate alm coefficients between 2 different arbitrary coordinate systems.
Routines to analyze a HEALPix sky map into its alm coefficients.
Routines to synthetize a HEALPix sky map from its alm coefficients.
alms2fits, dump_alms
Routines to save a set of alm in a FITS file.

Version 3.31, 2017-01-06