bl2fits

This IDL facility provides a means to write into a FITS file as an ascii table extension a (beam) window function $B(\ell)$. Adds additional headers if required. The facility is primarily intended to allow the user to write an arbitrary window function into a FITS file in the correct format to be ingested by the HEALPix simulation facilities synfast, isynfast, and others (see ”Beam window function files” in the HEALPix Fortran Facilities document).

Location in HEALPix directory tree: src/idl/fits/bl2fits.pro 

FORMAT

IDL> BL2FITS, bl_array, fitsfile, [HDR = , /HELP, XHDR =]

QUALIFIERS

bl_array

real or double array of Bl coefficients to be written to file. This has dimension (lmax+1,n) with $1\le n \le 3$, given in the sequence T E B.

fitsfile

String containing the name of the file to be written.

KEYWORDS

HDR=

String array containing the (non-trivial) primary header for the FITS file.

/HELP

If set, a help message is printed out, no file is written

XHDR=

String array containing the (non-trivial) extension header for the FITS file.

DESCRIPTION

bl2fits writes the input $B(\ell)$ coefficients into a FITS file containing an ascii table extension. Optional headers conforming to the FITS convention can also be written to the output file. All required FITS header keywords (like SIMPLE, BITPIX, ...) are automatically generated by the routine and should NOT be duplicated in the optional header inputs (they would be ignored anyway). The one/two/three column(s) are automatically named TEMPERATURE, GRAD, CURL respectively. If the window function is provided in a double precision array, the output format will automatically feature more decimal places.

RELATED ROUTINES

This section lists the routines related to bl2fits

idl

version 6.4 or more is necessary to run bl2fits.

fits2cl

provides the complimentary routine to read in a window function or power spectrum from a FITS file.

synfast

utilises the output file generated by bl2fits(option beam_file).

EXAMPLE:

beam1 = gaussbeam(10., 2000, 1)

beam2 = gaussbeam(15., 2000, 1)

beam = (beam1 + beam2) / 2.

bl2fits, beam, 'beam.fits'

bl2fits writes the beam window function stored in the variable beam (=Legendre transform of a circular beam) into the output FITS file beam.fits.