GNU Astronomy Utilities


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8.1.5.2 MakeProfiles profile settings

The profile parameters that differ between each created profile are specified through the columns in the input catalog and described in MakeProfiles catalog. Besides those there are general settings for some profiles that don’t differ between one profile and another, they are a property of the general process. For example how many random points to use in the monte-carlo integration, this value is fixed for all the profiles. The options described in this section are for configuring such properties.

--mode=STR

Interpret the center position columns (--ccol in MakeProfiles catalog) in image or WCS coordinates. This option thus accepts only two values: img and wcs. It is mandatory when a catalog is being used as input.

-r
--numrandom

The number of random points used in the central regions of the profile, see Sampling from a function.

-e
--envseed

Use the value to the GSL_RNG_SEED environment variable to generate the random Monte Carlo sampling distribution, see Sampling from a function and Generating random numbers.

-t FLT
--tolerance=FLT

The tolerance to switch from Monte Carlo integration to the central pixel value, see Sampling from a function.

-p
--tunitinp

The truncation column of the catalog is in units of pixels. By default, the truncation column is considered to be in units of the radial parameters of the profile (--rcol). Read it as ‘t-unit-in-p’ for ‘truncation unit in pixels’.

-f
--mforflatpix

When making fixed value profiles (flat and circumference, see ‘--fcol’), don’t use the value in the column specified by ‘--mcol’ as the magnitude. Instead use it as the exact value that all the pixels of these profiles should have. This option is irrelevant for other types of profiles. This option is very useful for creating masks, or labeled regions in an image. Any integer, or floating point value can used in this column with this option, including NaN (or ‘nan’, or ‘NAN’, case is irrelevant), and infinities (inf, -inf, or +inf).

For example, with this option if you set the value in the magnitude column (--mcol) to NaN, you can create an elliptical or circular mask over an image (which can be given as the argument), see Blank pixels. Another useful application of this option is to create labeled elliptical or circular apertures in an image. To do this, set the value in the magnitude column to the label you want for this profile. This labeled image can then be used in combination with NoiseChisel’s output (see NoiseChisel output) to do aperture photometry with MakeCatalog (see MakeCatalog).

Alternatively, if you want to mark regions of the image (for example with an elliptical circumference) and you don’t want to use NaN values (as explained above) for some technical reason, you can get the minimum or maximum value in the image 112 using Arithmetic (see Arithmetic), then use that value in the magnitude column along with this option for all the profiles.

Please note that when using MakeProfiles on an already existing image, you have to set ‘--oversample=1’. Otherwise all the profiles will be scaled up based on the oversampling scale in your configuration files (see Configuration files) unless you have accounted for oversampling in your catalog.

--mcolisbrightness

The value given in the “magnitude column” (specified by --mcol, see MakeProfiles catalog) must be interpretted as brightness, not magnitude. The zeropoint magnitude (value to the --zeropoint option) is ignored and the given value must have the same units as the input dataset’s pixels.

Recall that the total profile magnitude or brightness that is specified with in the --mcol column of the input catalog is not an integration to infinity, but the actual sum of pixels in the profile (until the desired truncation radius). See Profile magnitude for more on this point.

--magatpeak

The magnitude column in the catalog (see MakeProfiles catalog) will be used to find the brightness only for the peak profile pixel, not the full profile. Note that this is the flux of the profile’s peak pixel in the final output of MakeProfiles. So beware of the oversampling, see Oversampling.

This option can be useful if you want to check a mock profile’s total magnitude at various truncation radii. Without this option, no matter what the truncation radius is, the total magnitude will be the same as that given in the catalog. But with this option, the total magnitude will become brighter as you increase the truncation radius.

In sharper profiles, sometimes the accuracy of measuring the peak profile flux is more than the overall object brightness. In such cases, with this option, the final profile will be built such that its peak has the given magnitude, not the total profile.

CAUTION: If you want to use this option for comparing with observations, please note that MakeProfiles does not do convolution. Unless you have de-convolved your data, your images are convolved with the instrument and atmospheric PSF, see Point Spread Function. Particularly in sharper profiles, the flux in the peak pixel is strongly decreased after convolution. Also note that in such cases, besides de-convolution, you will have to set --oversample=1 otherwise after resampling your profile with Warp (see Warp), the peak flux will be different.

-X INT,INT
--shift=INT,INT

Shift all the profiles and enlarge the image along each dimension. To better understand this option, please see \(n\) in If convolving afterwards. This is useful when you want to convolve the image afterwards. If you are using an external PSF, be sure to oversample it to the same scale used for creating the mock images. If a background image is specified, any possible value to this option is ignored.

-c
--prepforconv

Shift all the profiles and enlarge the image based on half the width of the first Moffat or Gaussian profile in the catalog, considering any possible oversampling see If convolving afterwards. --prepforconv is only checked and possibly activated if --xshift and --yshift are both zero (after reading the command-line and configuration files). If a background image is specified, any possible value to this option is ignored.

-z FLT
--zeropoint=FLT

The zero-point magnitude of the image.

-w FLT
--circumwidth=FLT

The width of the circumference if the profile is to be an elliptical circumference or annulus. See the explanations for this type of profile in --fcol.

-R
--replace

Do not add the pixels of each profile over the background (possibly crowded by other profiles), replace them. By default, when two profiles overlap, the final pixel value is the sum of all the profiles that overlap on that pixel. When this option is given, the pixels are not added but replaced by the newer profile’s pixel and any value under it is lost.

When order matters, make sure to use this function with ‘--numthreads=1’. When multiple threads are used, the separate profiles are built asynchronously and not in order. Since order does not matter in an addition, this causes no problems by default but has to be considered when this option is given. Using multiple threads is no problem if the profiles are to be used as a mask with a blank or fixed value (see ‘--mforflatpix’) since all their pixel values are the same.

Note that only non-zero pixels are replaced. With radial profiles (for example Sérsic or Moffat) only values above zero will be part of the profile. However, when using flat profiles with the ‘--mforflatpix’ option, you should be careful not to give a 0.0 value as the flat profile’s pixel value.


Footnotes

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The minimum will give a better result, because the maximum can be too high compared to most pixels in the image, making it harder to display.


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