ctbkgcube

Generate background cube for a stacked analysis.

Synopsis

This tool generates a background cube for a stacked analysis based on an input model. A background cube is a 3-dimensional cube spanned by Right Ascension or Galactic longitude, Declination or Galactic latitude, and energy. The energy binning may be either linear, logarithmic, or custom defined using an input file. The input model is used to predict the expected number of background counts in each background cube bin.

ctbkgcube requires on input the event list or observation definition file that has been used in the generation of the counts cube using ctbin.

To assure consistency between an existing counts cube and the corresponding background cube, it is recommended to specify the counts cube as incube parameter. This will instruct ctbkgcube to extract the background cube definition (such as sky coordinates and projection, number of pixels, pixel scale, energy binning) from the counts cube.

ctbkgcube generates a background cube FITS file comprising two extensions. The primary extension contains a 3-dimensional image that contains the background cube values. The next extension named EBOUNDS contains a binary table that defines the energy boundaries of the background cube.

ctbkgcube generates also an output model XML file that can serve as input for a maximum likelihood analysis. The output model XML file is a copy of the input model XML file where the input background model has been replaced by a background model of type CTACubeBackground. The CTACubeBackground background model instructs any tool analysing binned data to extract background information from a background cube. The CTACubeBackground model has a spectral component that can be adjusted in a maximum likelihood fit to accomodate for uncertainties in the prediction of the energy dependence of the background rate. ctbkgcube will use a power law as spectral component, but you can replace this by any component of your choice.

General parameters

inobs [file]

Input event list or observation definition XML file.

inmodel [file]

Input model XML file.

incube [file]

Input counts cube file to extract background cube definition.

caldb [string]

Calibration database.

irf [string]

Instrument response function.

outcube [file]

Output background cube file.

outmodel [file]

Output model XML 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.

(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).

coordsysL <CEL|GAL> [string]

Coordinate system (CEL - celestial, GAL - galactic).

xref [real]

Right Ascension / Galactic longitude of cube centre (J2000, in degrees).

yref [real]

Declination / Galactic latitude of cube centre (J2000, in degrees).

proj <AIT|AZP|CAR|MER|MOL|STG|TAN> [string]

Projection method.

Standard parameters

(publish = no) [boolean]

Specifies whether the background 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 background 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 = ctbkgcube.log) [string]

Name of log file.

Related tools or scripts

ctbin