ialteralm


This IDL facility provides an interface to F90 'alteralm' facility. This program can be used to modify a set of alm spherical harmonics coefficients, as those extracted by ianafast or simulated by isynfast, before they are used as constraints on a isynfast run. Currently the alterations possible are
* rotation (using Wigner matrices) of the alm from the input coordinate system to any other standard astrophysical coordinate system. The resulting alm can be used with e.g. synfast to generate a map in the new coordinate system.
* removal of the pixel and beam window functions of the input alm (corresponding to the pixel size and beam shape of the map from which they were extracted) and implementation of an arbitrary pixel and beam window function.
\begin{displaymath}a_{lm}^{\rm OUT} = a_{lm}^{\rm IN} \frac{B^{\rm OUT}(l) P^{\rm
OUT}(l)}{B^{\rm IN}(l) P^{\rm IN}(l)},
\end{displaymath} (6)

where P(l) is the pixel window function, and B(l) is the beam window function (assuming a circular beam) or any other l space filter (eg, Wiener filter). For an infinitely small pixel (or beam) one would have P(l) = 1 (resp. B(l) = 1) for any l.

Location in HEALPix directory tree: src/idl/interfaces/ialteralm.pro 


FORMAT

IDL> IALTERALM, alm_in, alm_out, [ beam_file_in, beam_file_out, binpath=, coord_in, coord_out, epoch_in, epoch_out, fwhm_arcmin_in, fwhm_arcmin_out, /help, keep_tmp_files=, lmax_out, nlmax_out, nside_in, nside_out, nsmax_in, nsmax_out, /silent, tmpdir=, windowfile_in, winfiledir_in, windowfile_out, winfiledir_out ]


QUALIFIERS

alm_in
required input: input alm, must be a FITS file
alm_out
required output: output alm, must be a FITS file


KEYWORDS

binpath=
full path to back-end routine default:$HEXE/alteralm, then $HEALPIX/bin/alteralm
- a binpath starting with / (or $\backslash$),   or $ is interpreted as absolute
- a binpath starting with ./ is interpreted as relative to current directory
- all other binpathes are relative to $HEALPIX

beam_file_in=
Beam window function of input alm, either a FITS file or an array. If present, will override fwhm_arcmin_in default:value of BEAM_LEG keyword read from alm_in

beam_file_out=
Beam window function of output alm, either a FITS file or an array. If present and non-empty, will override fwhm_arcmin_out default:'' (empty string, no beam window applied)

coord_in=
Astrophysical coordinates system used to compute input alm. Case-insensitive single letter code. Valid choices are 'g','G' = Galactic, 'e','E' = Ecliptic, 'c','q','C','Q' = Celestial/eQuatorial. default:value of COORDSYS keyword read from alm_in

coord_out=
Astrophysical coordinates system of output alm. default: coord_in

epoch_in=
Astronomical epoch of input coordinates (coord_in) default:2000.0
epoch_out=
Astronomical epoch of output coordinates (coord_out) default:same as epoch_in

fwhm_arcmin_in=
Full Width Half-Maximum in arcmin of Gaussian beam applied to map from which are obtained input alm.
default:value of FWHM keyword in alm_in

fwhm_arcmin_out=
FWHM in arcmin to be applied to output alm.
default:fwhm_arcmin_in

/help
if set, prints extended help
/keep_tmp_files
if set, temporary files are not discarded at the end of the run

lmax_out=, nlmax_out=
maximum multipole of output alm

nside_in=, nsmax_in=
HEALPix resolution parameter of map from which were computed input alm default:determined from alm_in

nside_out=,nsmax_out=
HEALPix resolution parameter Nside whose window function will be applied to output alm.
Could be set to 0 for infinitely small pixels (no window) default:same as input nsmax_in

/silent
if set, works silently

tmpdir=
directory in which are written temporary files default:IDL_TMPDIR (see IDL documentation)

windowfile_in=
FITS file containing pixel window for nside_in default:determined automatically by back-end routine. Do not set this keyword unless you really know what you are doing

winfiledir_in=
directory where windowfile_in is to be found default:determined automatically by back-end routine. Do not set this keyword unless you really know what you are doing

windowfile_out=
FITS file containing pixel window for nside_out default:determined automatically by back-end routine. Do not set this keyword unless you really know what you are doing

winfiledir_out=
directory where windowfile_out is to be found default:determined automatically by back-end routine. Do not set this keyword unless you really know what you are doing


DESCRIPTION

ialteralm is an interface to 'alteralm' F90 facility. It requires some disk space on which to write the parameter file and the other temporary files. Most data can be provided/generated as an external FITS file, or as a memory array.


RELATED ROUTINES

This section lists the routines related to ialteralm

idl
version 6.4 or more is necessary to run ialteralm.
alteralm
F90 facility called by ialteralm.
ianafast
IDL Interface to F90 anafast and C++ anafast_cxx
iprocess_mask
IDL Interface to F90 process_mask
ismoothing
IDL Interface to F90 smoothing
isynfast
IDL Interface to F90 synfast


EXAMPLE:

ialteralm, !healpix.path.test+'alm.fits', '/tmp/alm_equat.fits', $
coord_in='g',coord_out='q'
isynfast, 0, alm_in='/tmp/alm_equat.fits', '/tmp/map_equat.fits'
mollview,'/tmp/map_equat.fits',1
mollview,'/tmp/map_equat.fits',2
This example script reads the test (polarised) alm located in $HEALPIX/test/alm.fits and rotates them from Galactic to Equatorial coordinates, it then synthetizes a map out of those, and finally plots its I and Q Stokes components (in Equatorial coordinates)

Version 3.31, 2017-01-06