pixel_window

This routine returns the averaged $\ell$-space window function $w_{\mathrm{pix}}(\ell)$ (for temperature and polarisation) associated to HEALPix pixels of resolution parameter $N_{\mathrm{side}}$. Because of the integration of the signal over the pixel area, the $a_{\ell m}^\mathrm{(pix)}$ coefficients of a pixelated map are related to the unpixelated underlying $a_{\ell m}$ by $a_{\ell m}^\mathrm{(pix)}= a_{\ell m}w_{\mathrm{pix}}(\ell)$.
Unless specified otherwise, the $w_{\mathrm{pix}}(\ell)$ 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) $w_{\mathrm{pix}}(\ell)$ generated. The first index must be $\ell_{\mathrm{max}}\leq 4N_{\mathrm{side}}$. 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 $N_{\mathrm{side}}$ resolution parameter. Unless windowfile is set, the file associated with $N_{\mathrm{side}}$ 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 $N_{\mathrm{side}}=64$.

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 $a_{\ell m}$ to emulate effect of real space filtering and coordinate rotation respectively

alm2map

synthetize a HEALPix map from its $a_{\ell m}$ (or $a_{\ell m}^\mathrm{(pix)}$).

alm2map_der

synthetize a map and its derivatives from its $a_{\ell m}$ (or $a_{\ell m}^\mathrm{(pix)}$).