ctexpcube
Generate exposure cube for a stacked analysis.
Synopsis
This tool generates an exposure cube for a stacked analysis. An exposure cube is a 3-dimensional cube spanned by Right Ascension or Galactic longitude, Declination or Galactic latitude, and energy, that gives the exposure as function of true sky direction and energy. The energy binning of the cube may be either linear, logarithmic, or custom defined using an input file.
ctexpcube requires on input the event list or observation definition file that has been used in the generation of the counts cube using :doc:`ctbin`.
The binning of an exposure cube does not need to correspond to the binning of a counts cube, as exposure values will in any case be determined by linear interpolation. For the user's convenience, however, the counts cube can be specified as incube parameter which will instruct ctexpcube to extract the exposure cube definition (such as sky coordinates and projection, number of pixels, pixel scale, energy binning) from the counts cube. Note, however, that the exposure cube is defined in true sky coordinates and energy while the counts cube is defined in measured sky coordinates and energy. Consequently, the sky area and energy range covered by the exposure cube should be slightly larger than that of the counts cube to accommodate for spill over of events due to the point spread function and energy dispersion. By computing the exposure cube on the same grid as the counts cube, the spill over of events from sources at the edge of cube will not be handled correctly.
Note that there should at least be 25 bins per energy decade in the exposure cube to assure that the energy dependence of the exposure is sufficiently well sampled (in particular at low energies).
ctexpcube generates an exposure cube FITS file comprising three extensions. The primary extension contains a 3-dimensional image that contains the exposure values. The next extension named ENERGIES contains a binary table that defines the energies of the exposure cube. The last extension named GTI contains a binary table that provides the Good Time Intervals of all observations that have been used for the computation of the exposure cube.
General parameters
- inobs [file]
- Input event list or observation definition XML file.
- incube [file]
- Input counts cube file to extract exposure cube definition.
- caldb [string]
- Calibration database.
- irf [string]
- Instrument response function.
- outcube [file]
- Output exposure cube file.
- ebinalg <FILE|LIN|LOG> [string]
- Algorithm for defining energy bins.
- emin [real]
- Lower energy value for first energy bin (in TeV).
- emax [real]
- Upper energy value for last energy bin (in TeV).
- enumbins [integer]
- Number of energy bins.
- ebinfile [file]
- Name of the file containing the energy bin definition.
- (addbounds = no) [boolean]
- Add energies to the exposure cube at the observation energy boundaries?
- (usepnt = no) [boolean]
- Use CTA pointing direction for cube centre instead of xref/yref parameters?
- nxpix [integer]
- Number of cube bins in Right Ascension or Galactic longitude.
- nypix [integer]
- Number of cube bins in Declination or Galactic latitude.
- binsz [real]
- Cube bin size (in degrees/pixel).
- coordsys <CEL|GAL> [string]
- Coordinate system (CEL - celestial, GAL - galactic).
- proj <AIT|AZP|CAR|GLS|MER|MOL|SFL|SIN|STG|TAN> [string]
- Projection method.
- xref [real]
- Right Ascension / Galactic longitude of cube centre (J2000, in degrees).
- yref [real]
- Declination / Galactic latitude of cube centre (J2000, in degrees).
Standard parameters
- (publish = no) [boolean]
- Specifies whether the exposure cube should be published on VO Hub.
- (chatter = 2) [integer]
- Verbosity of the executable:
chatter = 0: no information will be logged
chatter = 1: only errors will be logged
chatter = 2: errors and actions will be logged
chatter = 3: report about the task execution
chatter = 4: detailed report about the task execution
- (clobber = yes) [boolean]
- Specifies whether an existing output exposure cube file should be overwritten.
- (debug = no) [boolean]
- Enables debug mode. In debug mode the executable will dump any log file output to the console.
- (mode = ql) [string]
- Mode of automatic parameters (default is ql, i.e. "query and learn").
- (logfile = ctexpcube.log) [string]
- Name of log file.