XMM-Newton Science Analysis System: User Guide

5.7.1 Generating RGS images

Figure 40: The xmmselect Image panel is shown here for preparing a MLAMBDA/PI banana plot. Values have been specified for imageset, the image output file, and for a y-axis range suitable for the range of photon PI values. Pressing the Run button gets the work done.

Once the axes have been selected and any selection criteria specified, clicking the Image button initiates dialogue panels that include an Image section like the one shown in Fig. 40 which gives the opportunity to review the choices made. The MLAMBDA/PI images, commonly known as banana plots, are improved by overruling the default y-range by checking the withyranges box and setting, e.g. yimagemin=0, yimagemax=2500.

Fig. 41 shows plots of the merged RGS1 events. These plots are orthogonal projections of the all-important MLAMBDA,XDSP_CORR,PI 3-D RGS data space of the merged list of all the events detected in the observation, thus showing all the features of RGS data. The edges are clear of the 9 CCDs, numbered 1-9 from right to left. In both plots, wavelength and dispersion angle increase from left to right.

Figure 41: The MLAMBDA/XDSP_CORR and MLAMBDA/PI plots produced by xmmselect using ds9 for the merged RGS1 and RGS2 event lists of Mkn421 before filtering, thus showing all hot pixels and columns and other blemishes in addition to the bright smooth continuum of this active galaxy.

The pointing coordinates were evidently chosen well enough to put this bright source central in the aperture. The source was bright enough to be seen up to 4th or even a weak 5th order in the characteristic hyperbolic-shaped areas occupied by photons that have passed through the gratings. There are plenty of hot pixels and columns and the so-called fixed pattern noise shows as the herring-bone pattern in CCDs 1 and 2. Calibration sources of F K$\alpha$ at PI$=677$eV span CCDs 2&3 and 7&8 ; and Al K$\alpha$ at PI$=1487$eV span CCDs 3&4 and 8&9.

The locations of the selection regions may be checked using the task rgsimplot

http://xmm-tools.cosmos.esa.int/external/sas/current/doc/rgsimplot

which plots the regions over MLAMBDA-XDSP and MLAMBDA-PI images that are, in this case, most usefully generated from the screened events files. Fig. 42 shows such an example.

Figure 42: The MLAMBDA-XDSP_CORR and MLAMBDA-PI images produced by xmmselect from the screened event list can be shown with the selection regions using rgsimplot.