Ian M George: Spatial AnalysisThese pages are unofficial in all respects. They are primarily simply notes to myself. The information is not guaranteed to be correct or up-to-date.
Last Updated: 2004 Jun 30 Make a "Full" ImageNow we are going to make an image of all the data (in all CCDS) in celestial coordinates (primarily as a visual check). However we are going to first apply a filter such that only events with energies in the 0.5 - 8.0 keV band (as determined by the ACIS-S detector) are included. We use the FTOOL fselect to apply this filter:fselect cleaned.evt2 cleaned_0580.evts expr="((ENERGY.GE.500).AND.(ENERGY.LE.8000))" clobber=yes(note that the energy needs to be expressed in eV). So now we make the image (from the cleaned_0580.evts file) using the FTOOL f2dhisto: f2dhisto cleaned_0580.evts cleaned_0580.evts_img04 xbinsz=4 ybinsz=4 xcol=X ycol=Y xrange="INDEF,INDEF" yrange="INDEF,INDEF" clobber=yeswhere each pixel in the created image actually contains 4x4 ACIS-S detector pixels. Of course this image should be inspected using fv: fv cleaned_0580.evts_img04 &Most likely the default colortable/range chosen by fv will not be the most convenient. If you "Edit Image" and set plot to be log, set min to 0.1, max to 10 you should start to see something. VISUAL CHECK: What we expect to see is of course a 'classic' HETGS image consisting of the 0thorder image of the target (in most cases a 'point' source), along with the "X-shaped" dispersed spectra from the MEG & HEG. We are also looking to see whether there are any other 'obvious' X-ray sources and/or problems (such as unexpected detector artifacts) etc [New 04jun21] Searching for Serendipitous SourcesPossibly More Steps to Come...Onto the Next StepOther AXAF-related CribSheets Other CribSheets Ian M George Home Page |