pixel_window


This routine returns the averaged l-space window function $w_{\rm pix}(l)$ (for temperature and polarisation) associated to HEALPix pixels of resolution parameter ${N_{\rm side}}$. Because of the integration of the signal over the pixel area, the $a_{lm}^{\rm (pix)}$ coefficients of a pixelated map are related to the unpixelated underlying alm by $a_{lm}^{\rm (pix)}= a_{lm}w_{\rm pix}(l)$.
Unless specified otherwise, the $w_{\rm pix}(l)$ are read from the files $HEALPIX/data/pixel_window_n????.fits.

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


FORMAT

call pixel_window( pixlw, nside[, windowfile] )


ARGUMENTS

name & dimensionality kind in/out description
       
pixlw(0:lmax,1:p) DP OUT pixel window function(s) $w_{\rm pix}(l)$ generated. The first index must be $l_{\rm max}\leq 4{N_{\rm side}}$. The second index runs from 1:1 for temperature only, and 1:3 for polarisation. In the latter case, 1=T, 2=E, 3=B.
nside I4B IN HEALPix ${N_{\rm side}}$ resolution parameter. Unless windowfile is set, the file associated with ${N_{\rm side}}$ and shipped with the package is read by default. If nside = 0, the pixel is assumed infinitely small and pixlw is returned with value 1.
windowfile (OPTIONAL) CHR IN FITS file containing the pixel window to be read instead of the default.


EXAMPLE:

call pixel_window(pixlw, 64)
returns in pixlw the pixel window function for ${N_{\rm side}}=64$.


MODULES & ROUTINES

This section lists the modules and routines used by pixel_window.

misc_utils
module, containing:
assert, fatal_error
interrupt code in case of error
extension
module, containing:
getEnvironment
read environment variable
fitstools
module, containing:
read_dbintab
reads double precision binary table


RELATED ROUTINES

This section lists the routines related to pixel_window

gaussbeam
routine to generate a gaussian beam window function
generate_beam
returns a beam window function
alter_alm, rotate_alm
modifies alm to emulate effect of real space filtering and coordinate rotation respectively
alm2map
synthetize a HEALPix map from its alm (or $a_{lm}^{\rm (pix)}$).
alm2map_der
synthetize a map and its derivatives from its alm (or $a_{lm}^{\rm (pix)}$).

Version 3.31, 2017-01-06