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gteffbkg.txt
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NAME
gteffbkg - Creates maps of the effective background for a point
source as a function of position and energy
USAGE
gteffbkg cmap outfile irfs expcube bexpmap efact
DESCRIPTION
This tool is used to estimate the effective background that is
present for a point source as a function of position and energy.
This estimate is defined so that the square root of the effective
background is very close to the expected contribution to the
uncertainty on a likelihood fit for a point source coming from
statistical uncertainty of the background model. It can also
be used estimate the effect of systematic uncertainties of the
background model, when they can be parametrized as a fraction of
the effective background.
PARAMETERS
cmap [filename]
FITS file containing a counts cube representation of the
background model we want to compute the effective background for.
outfile [filename]
Name of the output FITS file that will contain the generated
effective background map.
irfs [string]
Instrument response functions. The instrument response (PSF,
effective area, energy resolution) is currently a function of
energy, inclination angle (the angle between the source and
the LAT normal) and photon category. Since the LAT will
usually survey the sky, a source will be observed at
different inclination angles. Each count will therefore be
characterized by a different instrument response function
(IRF). The default value is “CALDB”.
evtype [integer]
The evtype to be used in generating the background data. The
default is INDEF which will use the default in the input
file. This can be overridden by entering the desired event
type e.g. 3 for FRONT + BACK events.
expcube [filename]
FITS file containing livetime as a function of sky position
and off-axis angle. This file can be generated by gtltcube or
obtained from the FSSC website. See the gtltcube help for
further explanation.
bexpmap [filename]
Binned exposure map for on-the-fly source map
calculations. If the existing file is specified, that file
will be used as the exposure map. Otherwise, a map with that
name will be computed based on the energy bands in the
srcmaps file. If "none" is given (default value), the map
will be called "binned_exposure.fits".
efact [float]
Energy integration factor. For any particular energy E we
integrate the background from E/efact to E when we compute
the effective background.
(edisp_bins) [integer]
Number of extra bins to compute for energy dispersion purposes.
This needed to initialize the code, but is not actually used
in the computation of the effective background.
(chatter) [integer]
This parameter fixes the output verbosity: no screen output (0),
nominal screen output (2), maximum verbosity (4). Default is "2".
(clobber) [boolean]
If true, an existing file of the same name will be overwritten.
Default is "yes".
(debug) [boolean]
Activate debugging mode. Default is "no". When debug is "no",
all exceptions that are not caught and handled by individual
tool-specific code are caught by a top-level exception
handler that displays information about the exception and
then exits. When debug is "yes", such exceptions are not
caught by the top level code. Instead the tool produces a
segmentation violation, which is more useful for
debugging. When debugging mode is enabled, the tool produces
more verbose output describing any errors or exceptions that
are encountered.
(gui) [boolean]
Graphical User Interface (GUI) mode is activated if set to
"yes". Default is "no".
(mode) [string]
Mode of automatic parameters: "h" for batch, "ql" for
interactive. Default is "ql".
EXAMPLES
Parameters are passed following the FTOOLs model: They could be
passed answering from a prompt, as a list in a command line, or by
editing the parameter file.
To run gteffbkg simply type in the command line:
> gteffbkg
The parameter values have to be provided. Not all parameter are
prompted: some of them are "hidden". To change one of the "hidden"
parameter, the user should specify the values in the command line
or modify its mode by editing the parameter file. For example, to
avoid overwriting the outfile, the following command line has to
be typed:
> gteffbkg clobber=no
An example of how to run the tool is given below:
> gteffbkg
Input counts, source or model map file[] cmap.fits
Output File[] effbkg.fits
Response functions[CALDB]
Exposure cube[] expCube.fits
Binned exposure map[] bexposure.fits
Energy integration factor[2]
That last example could be also run in the command line as follows:
> gteffbkg cmap=cmap.fits outfile=effbkg.fits irfs=CALDB
expcube=expCube.fits bexpmap=bexposure.fits efact=2.
SEE ALSO
gtlike
gtsrcmaps
gtltcube
gtalphbkg
gtwtsmap