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create_alm*
This routine generates scalar (and tensor) alm for a temperature (and
polarisation) power spectrum read from an input FITS
file. The alm are gaussian distributed with a zero mean, and their
amplitude is multiplied with the l-space window function of a gaussian
beam characterized by its FWHM or an arbitrary circular beam
and a pixel window read from an external file.
Location in HEALPix directory tree:
src/f90/mod/alm_tools.f90
FORMAT call create_alm*(
nsmax, nlmax, nmmax, polar, filename, iseed, fwhm_arcmin, alm_TGC, header [,
windowfile, units, beam_file, rng_handle]
)
ARGUMENTS
| name & dimensionality |
kind |
in/out |
description |
|---|
| |
|
|
|
|
nsmax |
I4B |
IN |
Nside of the map to be synthetized from the alm
created by this routine. |
| nlmax |
I4B |
IN |
maximum l value to be considered (
MAX=3 x Nside). |
| nmmax |
I4B |
IN |
maximum m value for the alm. |
| polar |
I4B |
IN |
equals 1 if polarisation is used, 0 otherwise. |
| filename(LEN=filenamelen) |
CHR |
IN |
name of FITS file containing power spectrum. |
| rng_handle |
planck_rng |
INOUT |
structure containing
information necessary to continue a random sequence
initiated previously with the
subroutine rand_init. Consecutive calls to create_alm*can be made after a
single invocation to rand_init. |
| fwhm_arcmin |
SP/ DP |
IN |
FWHM size of the gaussian beam in arcminutes. |
| alm_TGC(1:p,0:nlmax,0:nmmax) |
SPC/ DPC |
OUT |
complex alm values generated from the powerspectrum in the FITS-file. The first index here runs form 1:1 for temperature only, and 1:3 for polarisation. In the latter case, 1=T, 2=E, 3=B. |
| header(LEN=80),dimension(60) |
CHR |
OUT |
part of header which
will be included in the FITS-file containing the
map synthesised from the alm which create_alm generates. |
| windowfile(LEN=filenamelen) (OPTIONAL) |
CHR |
IN |
full filename specification of the FITS file with the pixel window function. |
| units(LEN=80),dimension(1:) (OPTIONAL) |
CHR |
OUT |
physical units of the created
alm (square-root of the input power spectrum units). |
| beam_file(LEN=filenamelen) (OPTIONAL) |
CHR |
IN |
name of the file containing
the (non necessarily gaussian) window function Bl of a circular beam. If present, it will override
the argument fwhm_arcmin. |
EXAMPLE:
use alm_tools, only: create_alm
use rngmod, only: rand_init, rng_handle
type(planck_rng) :: rng_handle
call rand_init(rng_handle, -1)
call create_alm(64, 128, 128, 1, 'cl.fits', rng_handle, 5.0, alm_TGC, header, 'data/pixel_window_n0064.fits')
Creates scalar and tensor alm from the power spectrum given in the file
`cl.fits'. The map to be created from these alm is assumed to have
Nside=64. Cls from the power spectrum are used up to an l value of
128.
Corresponding alm values up to l=128 and m=128 are created as gaussian distributed
complex numbers. Their are drawn from a sequence of pseudo-random numbers
initiated with a seed of -1.
The produced alm are convolved with a gaussian beam of FWHM 5 arcminutes
and a pixel window read from 'data/pixel_window_n0064.fits'. It is assumed that after the return
from this routine, a map is generated from the created
alm. For this purpose, header is updated with FITS format information
describing the origin and history of these alm.
MODULES & ROUTINESThis section lists the modules and routines used by create_alm*.
-
alm_tools
- module, containing:
-
pow2alm_units
- routine to convert from power spectrum units to
alm units
-
generate_beam
- routine to generate beam window function
-
pixel_window
- routine to read in pixel window function
-
utilities
- module, containing:
-
die_alloc
- routine that prints an error message if there is not enough space for allocation of variables.
-
fitstools
- module, containing:
-
fits2cl
- routine to read a FITS
file containing a power spectrum.
-
read_dbintab
- routine to read a FITS-binary file containing the pixel window functions.
-
head_fits
- module, containing:
-
add_card
- routine to add a keyword to a FITS header.
-
get_card
- routine to read a keyword value from
FITS header.
-
merge_headers
- routine to merge two FITS headers.
-
rngmod
- module, containing:
-
rand_gauss
- function which returns a gaussian distributed random
number.
RELATED ROUTINESThis section lists the routines related to create_alm*
-
rand_init
- subroutine to initiate a random number sequence.
-
synfast
- executable using create_alm* to synthesize CMB maps from a given
power spectrum.
-
alm2map
- Routine to transform a set of alm created by create_alm* to a HEALPix map.
-
alms2fits, dump_alms
- Routines to save a set of alm in a FITS file.
Eric Hivon
2010-06-18
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