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You are here: Science»  IXO Simulation Tools»  IXO Simulator—simx

IXO Simulator—simx

Chandra image of Cas A

Chandra image of Cas A

Simulated image of Cas A based on Chandra image

Simulated image of Cas A

The simx 1.0.0 code simulates the IXO FMA response to an input point source or FITS image (from Chandra, XMM-Newton, or other source) and model X-ray spectrum. The tool incorporates a model of the 5 arcsec HPD PSF calculated at 6 keV, based on calculations for the glass optics design done by Paul Reid; the tool can incorporate other PSFs easily, once they become available.

The previous version of simx can be found here – simx-0.5.1.

The simulator uses response files to calculate the predicted response and effective area of various instruments; currently available are:

  • CalCore: The central 40 × 40 pixels, 3 arcsec on a side, for the calorimeter. These core pixels have the highest resolution (2.5 eV). The code also calculates pileup in the detector, separating events into high resolution, mid-resolution, and low-resolution.
  • CalFull: The full 52 × 52 pixels, 6 arcsec on a side, for the calorimeter. These pixels have lower spectral resolution (10 eV). The code also calculates pileup in the detector, separating events into high resolution, mid-resolution, and low-resolution. This model does not include a separate core array, instead simulating the entire array at the larger size. The deadtime for these larger pixels is significantly (160×) larger than the core array.
  • WFI/HXI: 1024 × 1024 pixels, 0.75 arcsec on a side. WARNING: Pileup in the WFI/HXI is complicated to calculate, and simx does not (yet) include these complications. Please do not use simx to test pileup for the WFI/HXI, as the answers will be incorrect.
  • Generic: A ‘generic’ mission, which uses user inputs for the focal length, pixel size, etc. These values are ignored if the mission is set to IXO.

The output is an OGIP-standard event file, which can be read by the ds9 image tool or used with the XSELECT or CIAO dmextract tools to create PHA spectrum files.

For bright sources, simx also estimates the number of counts which will have reduced resolution due to a ‘deadtime’-like effects. This includes calculations of the relative numbers of ‘High Res’, ‘Mid Res’, and ‘Low Res’ events for the calorimeter. As noted above, this problem is harder for the WFI/HXI and although a pileup fraction is calculated for the WFI/HXI, it should not be trusted. For bright sources, there is also an optional Bright Source Defocusing Optic (BSDO) filter mode which assumes a slumped microchannel plate has been inserted into the beam to diffuse the optic. This mode requires the use of special response matrices, which are supplied in the download.

The code has an option to include backgrounds, using the simulated background data available in the bkgnds directory. Note the README file in this directory, which explains how these files were created.

In the future we also plan to include the vignetting contribution, and extend the PSF model to beyond 100 arcsec, although neither of these effects are expected to be significant in most situations.

The code has is still in beta form, although is has been tested on Linux, OS X, and Solaris.

Please use the links below for more information on installing and running simx:

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