MAKECLUMPS - Create simulated data containing clumps and noise

Description:

This application creates a new 1-, 2- or 3-dimensional NDF containing a collection of clumps with background noise. It also creates a catalogue containing the clump parameters.

The clumps profiles are Gaussian, with elliptical isophotes. The values of each parameter defining the clump shape can be either fixed at a constant value or selected from a given probability distribution.

Usage:

makeclumps out outcat

Parameters:

ANGLE( 2 ) = _REAL (Read)

Defines the distribution from which the spatial position angle of the major axis of the elliptical clump is chosen. Values should be supplied in units of degrees. See parameter PARDIST for additional information. Note, angles are always taken from a uniform distribution, irrespective of the setting of PARDIST. [current value]

BEAMFWHM = _REAL (Read)

The spatial FHWM (Full Width at Half Max) of the instrumental beam, in pixels. The generated clumps are smoothed with a Gaussian beam of this FWHM, before noise is added. No spatial smoothing is performed if BEAMFWHM is zero. [current value]

DECONV = _LOGICAL (Read)

If TRUE, the clump properties stored in the output catalogue will be modified to take account of the smoothing caused by the instrumental beam width. [TRUE]

FWHM1( 2 ) = _REAL (Read)

Defines the distribution from which the FWHM (Full Width at Half Max) for pixel axis 1 of each clump is chosen. Values should be supplied in units of pixel. See parameter PARDIST for additional information. [current value]

FWHM2( 2 ) = _REAL (Read)

Defines the distribution from which the FWHM (Full Width at Half Max) for pixel axis 2 of each clump is chosen. Values should be supplied in units of pixel. See parameter PARDIST for additional information. [current value]

FWHM3( 2 ) = _REAL (Read)

Defines the distribution from which the FWHM (Full Width at Half Max) for pixel axis 3 of each clump is chosen. Values should be supplied in units of pixel. See parameter PARDIST for additional information. [current value]

LBND() = _INTEGER (Read)

The lower pixel bounds of the output NDF. The number of values supplied (1, 2 or 3) defines the number of pixel axes in the output NDF (an error is reported if the number of values supplied for LBND and UBND differ).

NCLUMP = _INTEGER (Read)

The number of clumps to create.

OUT = NDF (Write)

The NDF to receive the simulated data, including instrumental blurring and noise.

MODEL = NDF (Write)

The NDF to receive the simulated data, excluding noise. A CUPID extension is added to this NDF, containing information about each clump in the same format as produced by the FINDCLUMPS command. This includes an NDF holding an of the individual clump.

OUTCAT = FILENAME (Write)

The output catalogue in which to store the clump parameters. There will be one row per clump, with the following columns:

• PeakX: The PIXEL X coordinates of the clump peak value.

• PeakY: The PIXEL Y coordinates of the clump peak value.

• PeakZ: The PIXEL Z coordinates of the clump peak value.

• CenX: The PIXEL X coordinates of the clump centroid.

• CenY: The PIXEL Y coordinates of the clump centroid.

• CenZ: The PIXEL Z coordinates of the clump centroid.

• SizeX: The size of the clump along the X axis, in pixels.

• SizeY: The size of the clump along the Y axis, in pixels.

• SizeZ: The size of the clump along the Z axis, in pixels.

• Sum: The total data sum in the clump.

• Peak: The peak value in the clump.

• Area: The total number of pixels falling within the clump.

If the data has less than 3 pixel axes, then the columns describing the missing axes will not be present in the catalogue.

The "size" of the clump on an axis is the RMS deviation of each pixel centre from the clump centroid, where each pixel is weighted by the correspinding pixel data value. This excludes the instrumental smoothing specified by BEAMFWHM and VELFWHM.

PARDIST = LITERAL (Read)

The shape of the distribution from which clump parameter values are chosen. Can be "Normal" or "Uniform". The distribution for each clump parameter is specified by itw own ADAM parameter containing two values; the mean and the width of the distribution. If PARDIST is "Normal", the width is the standard deviation. If PARDIST is "Uniform", the width is half the range between the maximum and minimum parameter values. In either case, if a width of zero is supplied, the relevant parameter is given a constant value equal to the specified mean. [current value]

PEAK( 2 ) = _REAL (Read)

Defines the distribution from which the peak value (above the local background) of each clump is chosen. See parameter PARDIST for additional information. [current value]

RMS = _REAL (Read)

The RMS (Gaussian) noise to be added to the output data. [current value]

TRUNC = _REAL (Read)

The level (above the local background) at which clumps should be truncated to zero, given as a fraction of the noise level specified by RMS. [current value]

UBND() = _INTEGER (Read)

The upper pixel bounds of the output NDF. The number of values supplied (1, 2 or 3) defines the number of pixel axes in the output NDF (an error is reported if the number of values supplied for LBND and UBND differ).

VELFWHM = _REAL (Read)

The FWHM of the Gaussian velocity resolution of the instrument, in pixels. The generated clumps are smoothed on the velocity axis with a Gaussian beam of this FWHM, before noise is added. No velocity smoothing is performed if VELFWHM is zero. [current value]

VGRAD1( 2 ) = _REAL (Read)

Defines the distribution from which the projection of the internal velocity gradient vector onto pixel axis 1 of each clump is chosen. Values should be supplied in dimensionless units of "velocity pixels per spatial pixel". See parameter PARDIST for additional information. [current value]

VGRAD2( 2 ) = _REAL (Read)

Defines the distribution from which the projection of the internal velocity gradient vector onto pixel axis 2 of each clump is chosen. Values should be supplied in dimensionless units of "velocity pixels per spatial pixel". See parameter PARDIST for additional information. [current value]

Notes:

• If 3D data is created, pixel axes 1 and 2 are the spatial axes, and pixel axis 3 is the velocity axis.

• The positions of the clumps are chosen from a uniform distribution on each axis.