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])


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


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 )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 5.0 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

Eric Hivon 2003-02-07