The catalog containing information about each profile can be in the FITS ASCII, FITS binary, or plain text formats (see Tables). The latter can also be provided using standard input (see Standard input). 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 options213, 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. Profiles that are completely out of the image will not be created (unless you explicitly 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 do not 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.
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.
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, ‘
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.
sersic’ or ‘
moffat’ or ‘
gaussian’ or ‘
point’ or ‘
flat’ or ‘
circum’ or ‘
6’. A fixed value will be used for all pixels less than or equal to the truncation radius (\(r_t\)) and greater than \(r_t-w\) (\(w\) is the value to the --circumwidth).
distance’ or ‘
7’. At the lowest level, each pixel only has an elliptical radial distance given the profile’s shape and orientation (see Defining an ellipse and ellipsoid). When this profile is chosen, the pixel’s elliptical radial distance from the profile center is written as its value. For this profile, the value in the magnitude column (--mcol) will be ignored.
You can use this for checks or as a first approximation to define your own higher-level radial function. In the latter case, just note that the central values are going to be incorrect (see Sampling from a function).
custom-prof’ or ‘
8’. The values to use for each radial interval should be in the table given to --customtable. By default, once the profile is built with the given values, it will be scaled to have a total magnitude that you have requested in the magnitude column of the profile (in --mcol). If you want the raw values in the 2D profile (to ignore the magnitude column), use --mcolnocustprof. For more, see the description of --customtable in MakeProfiles profile settings.
azimuth’ or ‘
9’. Every pixel within the truncation radius will be given its azimuthal angle (in degrees, from 0 to 360) from the major axis. In combination with the radial distance profile, you can now create complex features in polar coordinates, such as tidal tails or tidal shocks (using the Arithmetic program to mix the radius and azimuthal angle through a function to create your desired features).
custom-img’ or ‘
10’. The image(s) to use should be given to the --customimg option (which can be called multiple times for multiple images). To identify which one of the images (given to --customimg) should be used, you should specify their counter in the “radius” column below. For more, see the description of
custom-imgin MakeProfiles profile settings.
The radius parameter of the profiles. Effective radius (\(r_e\)) if Sérsic, FWHM if Moffat or Gaussian.
For a custom image profile, this option is not interpreted as a radius, but as a counter (identifying which one of the images given to --customimg should be used for each row).
The Sérsic index (\(n\)) or Moffat \(\beta\).
The position angle (in degrees) of the profiles relative to the first FITS axis (horizontal when viewed in SAO DS9). When building a 3D profile, this is the first Euler angle: first rotation of the ellipsoid major axis from the first FITS axis (rotating about the third axis). See Defining an ellipse and ellipsoid.
Second Euler angle (in degrees) when building a 3D ellipsoid. This is the second rotation of the ellipsoid major axis (following --pcol) about the (rotated) X axis. See Defining an ellipse and ellipsoid. This column is ignored when building a 2D profile.
Third Euler angle (in degrees) when building a 3D ellipsoid. This is the third rotation of the ellipsoid major axis (following --pcol and --p2col) about the (rotated) Z axis. See Defining an ellipse and ellipsoid. This column is ignored when building a 2D profile.
The axis ratio of the profiles (minor axis divided by the major axis in a 2D ellipse). When building a 3D ellipse, this is the ratio of the major axis to the semi-axis length of the second dimension (in a right-handed coordinate system). See \(q1\) in Defining an ellipse and ellipsoid.
The ratio of the ellipsoid major axis to the third semi-axis length (in a right-handed coordinate system) of a 3D ellipsoid. See \(q1\) in Defining an ellipse and ellipsoid. This column is ignored when building a 2D profile.
The total pixelated magnitude of the profile within the truncation radius, see Profile magnitude.
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.
The options to set the WCS are the following: --crpix, --crval, --cdelt, --cdelt, --pc, cunit and ctype. Just recall that these options are only used if --background is not given: if the image you give to --background does not have WCS, these options will not be used and you cannot use WCS-mode coordinates like RA or Dec.
Read in other formats.
GNU Astronomy Utilities 0.20 manual, April 2023.