gaussbeam

This IDL facility provides the window function in $\ell$ 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 $\ell$ 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 $\ell$ space window function of a gaussian beam of FWHM Fwhm. For a sky of underlying power spectrum $C(\ell)$ observed with beam of given FWHM, the measured power spectrum will be $C(\ell)_{\mathrm{meas}} = C(\ell) B(\ell)^2$ where $B(\ell)$ 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$$ 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