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 pixelized map are related to the unpixelized underlying a_lm 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] )

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.

call pixel_window(pixlw, 64)

returns in pixlw the pixel window function for ${N_{\rm side}}=64$ .

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

Eric Hivon 2010-06-18

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