% synfast [options] [parameter_file]
Synfast reads the power spectrum from a file in ascii FITS format. This can contain either just the temperature power spectrum CTls or temperature and polarisation power spectra: CTl, CEl, CBl and CT x El (see Note 1, below). If simul_type = 2 synfast generates Q and U maps as well as the temperature map. The output map(s) is (are) saved in a FITS file. The Cls are used up to the specified llmax, which can not exceed 4 x nsmax. If simul_type = 3 or 4 the first derivatives of the temperature field or the first and second derivatives respectively are output as well as the temperature itself: T(p), , . If simul_type = 5 or 6 the first derivatives of the (T,Q,U) fields or the first and second derivatives respectively are output as well as the field themself: T(p), Q(p), U(p), ,
The random sequence seed for generation of alm from the power spectrum should be non-zero integer. If 0 is provided, a seed is generated randomly by the code, based on the current date and time. The map can be convolved with a gaussian beam for which a beamsize can be specified, or for an arbitrary circular beam for which the Legendre transform is provided. The map is automatically convolved with a pixel window function. These are stored in FITS files in the healpix/data directory. If synfast is not run in a directory which has these files, or from a directory which can reach these files by a `../data/' or `./data/' specification, the system variable HEALPIX is used to locate the main HEALPix directory and its data subdirectory is scanned. Failing this, the location of these files must be specified (using winfiledir). In the interactive mode this is requested only when necessary (see Notes on default directories on page ).
If some of the alm in the simulations are constrained eg. from observations, a FITS file with these alm can be read. This FITS file contains the alm for certain l and m values and also the standard deviation for these alm. The sky realisation which synfast produces will be statistically consistent with the constraining alm.
The code can also be used to generate a set of alm matching the input power spectra, beam size and pixel size with or without actually synthesizing the map. Those alm can be used as an input (constraining alm) to another synfast run.
Spherical harmonics values in the synthesis are obtained from a recurrence on associated Legendre polynomials . This recurrence consumed most of the CPU time used by synfast up to version 2.15. We have therefore included an option to load precomputed values for the from a file generated by the HEALPix facility plmgen. Since the introduction of accelerated spherical harmonic transforms in HEALPix v2.20, this feature is obsolete and should no longer be used.
Synfast will issue a warning if the input FITS file for the power spectrum does not contain the keyword POLNORM. This keyword indicates that the convention used for polarization is consistent with CMBFAST (and consistent with HEALPix 1.2). See the HEALPix Primer for details on the polarization convention and the interface with CMBFAST. If the keyword is not found, no attempt will be made to renormalize the power spectrum. If the keyword is present, it will be inherited by the simulated map.
Note 1: to allow the generation of maps (and alm) with and/or , see the subroutine create_alm.
|/data/pixel_window_nxxxx.fits||Files containing pixel windows for various nsmax.|
Synfast runs in interactive mode, self-explanatory.
When 'filename' is present, synfast enters the non-interactive mode and parses its inputs from the file 'filename'. This has the following structure: the first entry is a qualifier which announces to the parser which input immediately follows. If this input is omitted in the input file, the parser assumes the default value. If the equality sign is omitted, then the parser ignores the entry. In this way comments may also be included in the file. In this example, the file contains the following qualifiers:
Synfast reads in the Cl power spectrum in 'cl.fits' up to l=64, and produces the (RING ordered) map 'map.fits' which has . The map is convolved with a beam of FWHM 420.0 arcminutes. The sets the random seed for the realisation. A different would have given a different realisation from the same power spectrum.
were omitted, they take their default values (empty strings). This means that no file for constrained realisation or precomputed Legendre polynomials are read, the alm generated in the process are not output, and synfast attempts to find the pixel window files in the default directories (see page ).
- Initial release (HEALPix 0.90)
- Optional non-interactive operation. Proper FITS file support. Improved reccurence algorithm for which can compute to higher l values. Improved pixel windows averaged over actual HEALPix pixels. New functionality: constrained realisations, precomputed Plm. (HEALPix 1.00)
- New functionality: constrained realisations and pixel windows are now available for polarization as well. Arbitrary circular beams can be used. New parser (HEALPix 1.20)
- New functionnality: the generated alm can be output, and the map synthesis itself can be skipped. First and second derivatives of the temperature field can be produced on demand.
- New functionnality: First and second derivatives of the Q and U Stokes field can be produced on demand.
- Bug correction: corrected numerical errors on derivatives , , , for X=Q,U. See this appendix for details. (HEALPix 2.14)
|can not allocate memory for array xxx||Fatal||You do not have sufficient system resources to run this facility at the map resolution you required. Try a lower map resolution.|
this is not a binary table
|the fitsfile you have specified is not of the proper format|
|there are undefined values in the table!||the fitsfile you have specified is not of the proper format|
|the header in xxx is too long||the fitsfile you have specified is not of the proper format|
|XXX-keyword not found||the fitsfile you have specified is not of the proper format|
|found xxx in the file, expected:yyyy||the specified fitsfile does not contain the proper amount of data.|
Version 3.31, 2017-01-06