Making RMFs for extended sources

RGS response matrices as made in §8.4.5 are appropriate for use with point sources only. If we are interested in analyzing an extended source, the RMF must take into account the spatial degradation of the resolution. The most straight-forward way to do this is to modify the response matrix prior to spectral fitting. For sources extended up to about 1 arcminute, this can be done with the FTOOL rgsrmfsmooth. It requires three files: the point source RMF (as made in §8.4.5), an image of the source (from an EPIC camera, see §7.3.1, or different mission), and a text file. The better the resolution of the image, the more accurate the modified RMF will be, so if a Chandra image is available for a source, it should be used instead of an EPIC image. The text file must list the name of the image, the boresight, and the aperture size in the following format:

RGS_XSOURCE_IMAGE <name of source image>
RGS_XSOURCE_BORESIGHT <image boresight: RA (h:m:s), DEC(degrees:m:s), and PA (decimal
$$ degrees)>
RGS_XSOURCE_EXTRACTION <source radius in arcminutes>

For an example case, we will name our text file xsource.mod. We will assume that a RMF for the first order grating was made as in §8.4.5 and an MOS1 image was made as in §7.3.1; xsource.mod contains these lines:

RGS_XSOURCE_IMAGE my_MOS1_image.fits
RGS_XSOURCE_BORESIGHT 05:28:45 -65:26:55 219.769546508789
RGS_XSOURCE_EXTRACTION 1.2

This file can be made on the user's local machine and uploaded to the Hera server by right-clicking and dragging the file from the Local Directory panel to the Remote Directory.

To make an RMF for an extended source in the Command Window, type:

rgsrmfsmooth rmffil=my_ps_rmf.fits imgfil=xsource.mod order=1 outfil=my_es_rmf.fits

where

rmffil - the point source RGS RMF
imgfil - the text file with the name of the source image, boresight, and extraction region
order - grating order of RMF
outfil - output RMF name