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Creating New Components

The first step is to create some model components.

Move the pointer over the black background of the editing area and press the BMenu button. Select the Add Component command from this menu (all of the other commands should be ``greyed out'' to show that they are not available at this time. You will get the Add Component dialogue as shown in Figure 2.3.

  figure187
Figure 2.3: The Add Component Dialogue. 

All dialogues in SLIME follow the conventional OSF/Motif pattern. There is a work area where you enter the information necessary for the dialogue to do its task and an action area that contains a number of buttons. You can click on either the OK button or the Apply button to make the dialogue complete its task. These buttons differ in that the dialogue will be dismissed when you click on the OK button but will stay up if you click on the Apply button. In some cases it might be confusing to retain the dialogue after taking the action it specifies: these dialogues will not have an Apply button. If you change your mind about performing the action controlled by the dialogue you can dismiss the dialogue without taking any other action by clicking on the Cancel button. You can also click on the Help button to request help on using the dialogue.

The work area of the Add Component dialogue contains an option menu that is used to select the type of the component that you can add and a set of type-in fields that specify the parameters of the model. You may create point components, which have negligable extent, optically thin spheres and elliptical, Gaussian brightness distributions. Note the fields change as you change the component type since some parameters are only applicable to certain types of component. The full set of parameters is listed below.

Flux
The flux density of the component in Jy.

RA Offset
The RA offset of the peak of the component from the phase centre in millarcseconds, increasing to the right (West).

Declination Offset
The declination offset of the peak of the component from the phase centre in milliarcseconds, increasing towards the top (North).

Diameter
The diameter of the component in milliarcseconds (spheres only).

Primary Axis
The full-width to half-maximum of the component in milliarcseconds along its primary axis (Gaussian components only). The two axes of an elliptical Gaussian are arbitrarily labelled as the primary and secondary axis so that they may be distinguished without reference to their relative lengths.

Secondary Axis
The full-width to half-maximum of the component in milliarcseconds along its primary axis (Gaussian components only).

Position Angle
The position angle of the primary axis in degrees (Gaussian components only).

The Add Component dialogue will create a new component with the specified parameters every time you click the OK or Apply buttons. Use this dialogue to create a point component, a sphere and a Gaussian component in that order, all with zero offsets from the centre of the field.

You will see each component appear in the centre of the editing area. Each successive component will appear on top of the existing components, probably obscuring them. The next two sections will show you how to move them around.


next up previous contents
Next: Changing Component Parameters with Up: Using the Model Editing Previous: Using the Model Editing

Chris Flatters
Thu Mar 14 16:02:50 MST 1996