Next: rgsxsrc: convolve an RGS Up: Convolution Model Components Previous: rfxconv: angle-dependent reflection from Contents
rgsext: convolve an RGS spectrum for extended emission
This model convolves the input spectrum by an angular structure function so that it can be used with the standard RGS response matrix, which assumes a point source. This will only be of value for moderately extended (one arcmin) sources. It is a modification of the rgsxsrc model with an extra parameter to provide additional smoothing above that provided by the image. The smoothing factor stretches the angular structure function by the parameter value.
The angular structure function depends on an input image, boresight position and extraction region size. There are two ways of passing this information to the model. Either the information can be given by three XFLTnnnn keywords in the spectrum or the information can be read from an external file.
An example of the first option is to include the keywords:
XFLT0001 = 'Image:/local/data/mymachine/myusername/mos1.fit' XFLT0002 = 'Boresight:05:25:02.9 -69:38:30 339.760974' XFLT0003 = 'Extraction:1.8'
For the second option, the xset variable RGS_XSOURCE_FILE should be set to the name of the file containing the information. An example of this file is:
RGS_XSOURCE_IMAGE /local/data/mymachine/myusername/mos1.fit RGS_XSOURCE_BORESIGHT 05:25:02.9 -69:38:30 339.760974 RGS_XSOURCE_EXTRACTION 1.8
The RA and Dec of the source can be determined from the image or from the headers of the source spectrum. The position angle can be found in the image headers.
The model parameters are:
| par1 | order: grating order (must be negative) |
| par2 | factor: additional smoothing factor (1 means no change) |