XMM-Newton Science Analysis System: User Guide

4.7.2 Image generation with xmmselect

An alternative (and more interactive) approach is to create images via the xmmselect GUI, which is started with the command:

xmmselect table=inevlist.fits

Afterwards, the following steps need to be performed to generate and display an EPIC image:

1. Choose X and Y in the Column selection (input columns for the image, e.g. X and Y (sky coordinates), RAWX and RAWY (raw CCD-specific coordinates) or DETX and DETY (camera-specific coordinates) and click in the Product selection part on the "Image" tab (see figure 16). This will start the general window of the evselect task.

   Caution: if x/ycolumn in evselect are the CCD raw coordinates RAWX and RAWY, all selected CCDs will be projected on top of each other. If an image in RAWX and RAWY is needed e.g. for diagnostic purposes, an additional filter expression selecting a single CCD only should be applied. In order to get an image of all active CCDs in the camera, the x/ycolumn should be set to X and Y or DETX and DETY.

   Figure 16: In the xmmselect main window, an image can be extracted by selecting X/Y as image axis and by pressing the "Image" button.

   

2. In the evselect main window (figure 17) one now has the option to apply further events filtering (if not yet specified in the xmmselect main window). If one is happy with the set-up, the next step is to click on the "Image" button on the top of the GUI.

   Figure 17: The evselect main window, where e.g. the selection expression still can be modified.

   

3. In the now visible evselect window with the image creation related parameters (figure 18) one needs to specify a name for the output image (parameter imageset). By default, events will be binned into an image with 600 x 600 square pixels. The image size can be modified as well as the binning mode: setting Binning to binSize allows e.g. to project events onto a grid with specified pixelsize (a value of x/yimagebinsize=100, e.g. will result in 5 x 5 arcsec pixels).

   Figure 18: The evselect window with the image related parameters, where e.g. the output image name and the binning of the events can be modified.

   

4. Click on the "Run" button to start the image creation process. After the image is created and stored in the working directory, xmmselect will automatically launch the image viewer. The ds9 viewer allows the user to zoom in on a region of special interest, to change the intensity scale and the color. The position of the mouse pointer is displayed (in RA and Dec in case of a sky image, or in linear coordinates in case of a camera or raw coordinate image). For details on the image viewer (developed by Smithsonian Astrophysical Observatory), follow the links to further information that are available under the ds9 "Help" button.

Note, if running the image creation for a second time with the same name for the output image (parameter imageset), the previously created image file will be overwritten. This can be avoided by starting xmmselect with the "-c" (no clobber) option (see documentation of the taskmain SAS package).