gaussbeam


This IDL facility provides the window function in l space for a gaussian axisymmetric beam of given FWHM.

Location in HEALPix directory tree: src/idl/misc/gaussbeam.pro 


FORMAT

IDL> beam=GAUSSBEAM(Fwhm, Lmax [, Dim, HELP=])


QUALIFIERS

Fwhm
Full Width Half Maximum of the gaussian beam, in arcmin (scalar real)
Lmax
the window function is computed for the multipoles l in {0,...,Lmax}
Dim
scalar integer, optional.
If absent or set to 0 or 1, the output has size (Lmax+1) and is the temperature beam;
if set to $2 \le$ Dim $\le 4$ , the output has size (Lmax+1,Dim) and contains in that order :
the TEMPERATURE beam,
the GRAD/ELECTRIC polarization beam
the CURL/MAGNETIC polarization beam
the TEMPERATURE*GRAD beam
HELP=
if set, prints out the help header and exits


DESCRIPTION

gaussbeam computes the l space window function of a gaussian beam of FWHM Fwhm. For a sky of underlying power spectrum C(l) observed with beam of given FWHM, the measured power spectrum will be $C(l)_{\rm meas} = C(l)
B(l)^2$ where B(l) is given by gaussbeam(Fwhm,Lmax). The polarization beam is also provided (when Dim > 1) assuming a perfectly co-polarized beam (eg, Challinor et al 2000, astro-ph/0008228)


RELATED ROUTINES

This section lists the routines related to gaussbeam

idl
version 6.4 or more is necessary to run gaussbeam
healpixwindow
computes the tex2html_wrap_inline$l$ space window function associated with a HEALPix pixel size
synfast
f90 code to generate CMB maps of given power spectrum convolved with a gaussian beam
smoothing
f90 code to smooth existing HEALPix maps with a gaussian beam
anafast
f90 code to compute the power spectrum of a HEALPix sky map


EXAMPLE:

beam = gaussbeam(5.,1200)
beam contains the window function in {0,...,1200} of a gaussian beam of fwhm 5 arcmin

Version 3.31, 2017-01-06