selection of bright regions only

From: Bryan Gaensler (bgaensler@cfa.harvard.edu)
Date: Thu Aug 21 2003 - 08:43:13 EDT


Hi all,

I have some ACIS data of a complicated extended source. I have reason to
believe that the bright regions and faint regions have different spectra,
and would like to see if this is indeed the case.

One thing I can do is draw boxes around all the bright areas by hand,
and then extract the appropriate spectrum. But does anyone know if
there is a way within CIAO to extract a spectrum from an event file
corresponding to those pixels in the image which are brighter than a
certain threshold? I.e. is there I way I can get the spectrum only of
those image pixels with (say) >10 counts in them?

Bryan



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