Subsections

• E..3.1 Actions
• E..3.2 Usage and Inputs
• E..3.3 Data Products

E..3 EXTRACT_SPECTRA Stage

This stage is run for each observation to perform the final spectral extraction in preparation for spectral fitting, as shown in Figure 8.

E..3.1 Actions

• All actions from the EXTRACT_EVENTS stage (§E.2) are performed.

• Source spectra are extracted.

• Statistics that characterize the exposure map pixels that fall in the extraction region are saved in the keywords EMAP_NUM, EMAP_AVG, EMAP_MED, EMAP_MIN, EMAP_MAX.

• ARF and RMF files are constructed. Note that AE will re-use any source RMFs existing from an earlier extraction in order to avoid long-running calls to the tool mkacisrmf.

• Plots summarizing the results of EXTRACT_SPECTRA are presented. These plots are diagnostic tools that help you spot problems in your data, in your catalog, in your CIAO configuration, in the CIAO software, or in the AE software. Some plots may also convey scientifically interesting information about your sources. For historical reasons some of the plots in this stage use information from the TIMING stage, so run EXTRACT_SPECTRA then TIMING then EXTRACT_SPECTRA with the /PLOT option.

E..3.2 Usage and Inputs

The CIAO tools used in this stage require that you configure ardlib.par for the observation you're processing:

• The ardlib.par file must point to an appropriate bad pixel file, which is used by mkarf. Generally each observation has its own bad pixel file, which may have been augmented by the observer during data reduction. The CIAO tool acis_set_ardlib will help you configure an ardlib.par file for your observation.

• The AXAF_ACIS?_QEU_FILE parameters in ardlib.par must specify an appropriate set of QEU (quantum efficiency uniformity) files, which are used by mkarf. If the data have been through the Townsley et al. CTI corrector then the QEU files supplied with that corrector must be specified (e.g. with pset), rather than the standard value of ``CALDB''. At PSU, these files are /usr/common/Townsley_CTI_corrector/public/120C/ccd?_120.qeu[1] or /usr/common/Townsley_CTI_corrector/public/110C/ccd?_110.qeu[1].

• The AXAF_RMF_FILE parameter in ardlib.par must specify an appropriate source for constructing RMF files. Normally, this is set to its default value, 'CALDB'. However, if the data have been through the Townsley et al. CTI corrector then AXAF_RMF_FILE should be set (e.g. with pset) to the path to a directory that contains the appropriate set of RMF files supplied with the CTI corrector. (At Penn State that path is /usr/common/Townsley_CTI_corrector/public/120C/ or /usr/common/Townsley_CTI_corrector/public/120C/)

AE will print the relevant parts of ardlib.par and pause briefly for you to review these, to make sure that the correct ardlib.par file is being referenced and that it contains the correct bad pixel, QEU, and RMF entries.

acis_extract, srclist_filename, obsname, obsdata_filename, /EXTRACT_SPECTRA, ENERGY_RANGE=[energy,energy], EMAP_FILENAME=filepath, ASPECT_FN=filepath, ASPHIST_DIR=directory, ARDLIB_FILENAME=filepath, PBKFILE=filepath, MSKFILE=filepath, WARNING_REGION_FILENAME=filepath, NEIGHBORHOOD_SIZE=value, /REUSE_NEIGHBORHOOD, /USE_MKRMF, EMAP_ENERGY=energy, WMAP_ENERGY_RANGE=energy

acis_extract, srclist_filename, obsname, /EXTRACT_SPECTRA, /PLOT

EXAMPLE:
idl $\vert\&$ tee extract_spectra_1875.log

acis_extract, 'all.srclist', '1875', '../obs1875/spectral.evt', /EXTRACT_SPECTRA, ENERGY_RANGE=[0.5,8], EMAP_FILENAME='../obs1875/obs.emap', ASPECT_FN='../obs1875/obs.asol', ASPHIST_DIR='../obs1875/asphist', ARDLIB_FILENAME='../obs1875/ardlib.par', PBKFILE='../obs1875/obs.pbkfile', MSKFILE='../obs1875/obs.mskfile, WARNING_REGION_FILENAME='warning.reg'

acis_extract, 'all.srclist', '1875', /EXTRACT_SPECTRA, /PLOT

• The optional ENERGY_RANGE parameter defines the band over which statistics are computed; default is [0.5,8.0]. An energy filter is NOT applied to the spectra.

• The optional parameter ASPECT_FN is recommended so that various CIAO tools (e.g. dmcoords, mkacisrmf, mkwarf) can be supplied with an aspect file.

• The ASPHIST_DIR should be the path to a directory that contains appropriate aspect histogram files for each active CCD with names ccd0.asphist, ccd1.asphist,... Each CCD must have its own aspect histogram file because the tool asphist considers a CCD's GTI table when computing the aspect histogram. If omitted the directory ./asphist/ is assumed. Methods of constructing are aspect histograms are discussed in the CIAO documentation. If you use the CIAO script merge_all to construct SINGLE ObsId exposure maps you can rename the aspect histograms files it produces, e.g. merged_asp_0.fits $\rightarrow$ ccd0.asphist. If you use the AE tool ae_make_emap (§7.14) to construct exposure maps then an aspect histogram directory named asphist with the correct file names is produced.

  AE confirms that the exposure times represented in the aspect histograms supplied are similar to the EXPOSUR* keywords in the event data as a potential aide in catching mistakes in aspect histogram construction.

• The required ARDLIB_FILENAME should be the path to an ardlib.par parameter file that has been correctly configured for this observation. To avoid mistakes we STRONGLY recommend that you store a correctly configured ardlib.par in the area where you reduced the observation, rather than in the default parameter directory referenced in your shell's PFILES environment variable.

• The optional PBKFILE parameter enables the ``Dead Area calibration'' available in the mkarf/mkwarf tools. See the ahelp documentation in CIAO or the appropriate CIAO thread.

• The optional MSKFILE parameter should be the path to the observation's ``mask file'', which is used by mkarf and mkwarf.

• See §E.2 for a description of the WARNING_REGION_FILENAME, NEIGHBORHOOD_SIZE, and REUSE_NEIGHBORHOOD parameters.

• Supply /USE_MKRMF to build RMFs using the CIAO tool mkrmf instead of the tool mkacisrmf. The CXC recommends the mkrmf tool only for data taken at -110 C on certain CCDs.

• The keyword parameter EMAP_ENERGY must be supplied for diffuse sources (§7.1.2); it should specify the mono-energy (in keV) that was used to build the exposure map (§7.14.3). You can look up this energy in the headers of the ``instrument maps'' produced by CIAO, for example

    dmlist asphist/ccd0.instmap head | egrep "ENERG_LO|ENERG_HI"
  

• The optional keyword parameter WMAP_ENERGY_RANGE can be supplied for diffuse sources (§7.1.2) to specify the energy range (in keV) over which a ``weight map'' (needed by mkwarf) is constructed ; the default range is 0.5-2 keV.

E..3.3 Data Products

For each source the following files are produced:

All data products from the EXTRACT_EVENTS stage (§E.2) are also produced by EXTRACT_SPECTRA.

{sourcename}/{obsname}/source.pi:

the spectrum of the source

{sourcename}/{obsname}/source.rmf:

the RMF at the source position for the CCD containing the majority of the band-limited events in source.evt

{sourcename}/{obsname}/sourcei.arf:

the ARF at the source position for CCD i

{sourcename}/{obsname}/source.arf:

the multi-CCD, PSF fraction reduced ARF at the source position

{sourcename}/{obsname}/obs.stats:

a FITS file containing keyword information about this observation of the source

Several interactive plots show characteristics of the source extraction; see our AE recipes (§7.1) for descriptions of each.