GNU Astronomy Utilities


Next: , Previous: , Up: Invoking astmkprof   [Contents][Index]


8.1.5.1 MakeProfiles catalog

The catalog containing information about each profile can be in the FITS ASCII, FITS binary, or plain text formats (see Tables). Its columns can be ordered in any desired manner. You can specify which columns belong to which parameters using the set of options discussed below. For example through the --rcol and --tcol options, you can specify the column that contains the radial parameter for each profile and its truncation respectively. See Selecting table columns for a thorough discussion on the values to these options.

The value for the profile center in the catalog (the --ccol option) can be a floating point number so the profile center can be on any sub-pixel position. Note that pixel positions in the FITS standard start from 1 and an integer is the pixel center. So a 2D image actually starts from the position (0.5, 0.5), which is the bottom-left corner of the first pixel. When a --background image with WCS information is provided or you specify the WCS parameters with the respective options, you may also use RA and Dec to identify the center of each profile (see the --mode option below).

In MakeProfiles, profile centers do not have to be in (overlap with) the final image. Even if only one pixel of the profile within the truncation radius overlaps with the final image size, the profile is built and included in the final image image. Profiles that are completely out of the image will not be created (unless you explicity ask for it with the --individual option). You can use the output log file (created with --log to see which profiles were within the image, see Common options.

If PSF profiles (Moffat or Gaussian, see Point Spread Function) are in the catalog and the profiles are to be built in one image (when --individual is not used), it is assumed they are the PSF(s) you want to convolve your created image with. So by default, they will not be built in the output image but as separate files. The sum of pixels of these separate files will also be set to unity (1) so you are ready to convolve, see Convolution process. As a summary, the position and magnitude of PSF profile will be ignored. This behavior can be disabled with the --psfinimg option. If you want to create all the profiles separately (with --individual) and you want the sum of the PSF profile pixels to be unity, you have to set their magnitudes in the catalog to the zero-point magnitude and be sure that the central positions of the profiles don’t have any fractional part (the PSF center has to be in the center of the pixel).

The list of options directly related to the input catalog columns is shown below.

--ccol=STR/INT

Center coordinate column for each dimension. This option must be called two times to define the center coordinates in an image. For example --ccol=RA and --ccol=DEC (along with --mode=wcs) will inform MakeProfiles to look into the catalog columns named RA and DEC for the Right Ascension and Declination of the profile centers.

--fcol=INT/STR

The functional form of the profile with one of the values below depending on the desired profile. The column can contain either the numeric codes (for example ‘1’) or string characters (for example ‘sersic’). The numeric codes are easier to use in scripts which generate catalogs with hundreds or thousands of profiles.

The string format can be easier when the catalog is to be written/checked by hand/eye before running MakeProfiles. It is much more readable and provides a level of documentation. All Gnuastro’s recognized table formats (see Recognized table formats) accept string type columns. To have string columns in a plain text table/catalog, see Gnuastro text table format.

--rcol=STR/INT

The radius parameter of the profiles. Effective radius (\(r_e\)) if Sérsic, FWHM if Moffat or Gaussian.

--ncol=STR/INT

The Sérsic index (\(n\)) or Moffat \(\beta\).

--pcol=STR/INT

The position angle (in degrees) of the profiles relative to the first FITS axis (horizontal when viewed in SAO ds9).

--qcol=STR/INT

The axis ratio of the profiles (minor axis divided by the major axis in a 2D ellipse).

--mcol=STR/INT

The total pixelated magnitude of the profile within the truncation radius, see Profile magnitude.

--tcol=STR/INT

The truncation radius of this profile. By default it is in units of the radial parameter of the profile (the value in the --rcol of the catalog). If --tunitinp is given, this value is interpreted in units of pixels (prior to oversampling) irrespective of the profile.


Next: , Previous: , Up: Invoking astmkprof   [Contents][Index]