|HETGS Line Profiles|
Validation of LSF: Line Profile
We check the validity of the LSF library with marx. A mono-energetic marx simulated HETG grating dataset is processed and its line spectrum is extracted with its default setting using CIAO and DS tools (version 2.2.1 used). An appropriate set of RMF is generated based on the new LSF library. With all the files in hand, we use isis to fit a delta function on the extracted line profile. If the RMF is generated properly (and hence the LSF library contains an accurate set of parameters that describes instrument line spread function), then this would result in a reasonable fit without any significant residuals. (Note that the same testing can be done via a Gaussian fit with a extremely small Gaussian width value).
In Table 1 below, we show the results of the testing. We run a number of mono-energetic marx simulations with ACIS-S/HETG (LETG LSF not ready at this point); the Event L1 files are processed and their spectra are extracted with an extraction width = 0.00199 degrees, which is very close to the default width. The fittings were performed on both HEG and MEG. Click on the links in the table to view a fitting result. Each image shows the fitting curve (in red) and the residual of a fit in the lower panel.
Table 1a: Validation of +1st Order Line Profiles at Various Energies.
Table 1b: Validation of -1st Order Line Profiles at Various Energies.
As the users can see, the derived RMFs from the new LSF library can give a desent description of mono-energetic line profiles at various energy values. A number of similar tests are conducted with different extraction widths and their results are practically identical to what is demonstrated here.
Incidentally, the users are encouraged to perform a simular validation with marx if one looks to detect a sign of line skewness via profile fitting.
This page was last updated Apr 11, 2003 by Bish K. Ishibashi. To comment on it or the material presented here, send email to email@example.com.