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gtpsf.txt
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NAME
gtpsf - Calculates the effective point spread function, as a
function of energy at a given source location, averaged
over an observation.
USAGE
gtpsf expcube outfile irfs ra dec emin emax nenergies thetamax ntheta
DESCRIPTION
This tool calculates the effective point spread function (PSF), as a
function of energy at a given source location, averaged over an
observation. The PSF and theta values are stored in different
extensions of the output FITS file (#1 and #2, respectively).
The units of each PSF are sr^{-1}: Integrating each PSF over theta
and azimuthally, unity is obtained.
PARAMETERS
expcube [filename]
FITS file containing livetime as a function of sky position
and off-axis angle also referred to as the "exposure
hypercube file". This file should be generated by gtltcube.
outfile [filename]
Name of the output FITS file.
(outtable) [string]
Name of the output file binary table extension which contains the
results. Default is "PSF".
irfs [string]
Instrument response function. Default is "P7SOURCE_V6".
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.
ra [double]
Right Ascension (J2000) of desired source position in
decimal degrees.
dec [double]
Declination (J2000) of desired source position in
decimal degrees.
emin [double]
Minimum of the energy range covered, in MeV. The range of this
parameter depends on the response function used. Currently it is
recommended that emin be larger or equal to 18 MeV. Default is "20".
emax [double]
Maximum of the energy range covered, in MeV. The range of this
parameter depends on the response function used. Currently it is
recommended that emax be smaller or equal to 5.6e6 MeV. Default is
"2e5".
nenergies [integer]
Number of logarithmically spaced energies. It should be larger
than 1. Default is "20".
thetamax [double]
Maximum angle of apparent photon direction with respect to the
source direction (degrees). Default is "30". The lowest value
for this parameter is inversely proportional to the minimum energy
considered: Some tens of degrees are necesssary to sample
correctly the PSF at energies of a few MeV.
ntheta [integer]
Number of theta bins. The bins are spaced as a power of 2 (y=ax^2,
where a=(thetamax/ntheta^2). Default is "300". The lowest value
for this parameter should be no less than a few to have a reasonable
representation of the PSF shape.
(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
gtpsf handles parameters following the FTOOLs model: They
can be passed by answering a prompt or as a list in a command
line. This facilitates calling gtpsf from a script.
To be prompted for gtpsf options type in the command line:
>gtpsf
The user will be prompted for the parameter values. 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, if the user does not want to overwrite the
existing output file, the user should set the parameter "clobber=no", e.g.:
>gtpsf clobber=no
An example of how to run the tool is given below:
> gtpsf
Livetime cube file[] expCube.fits
output file name[] psf.fits
Response functions[P7SOURCE_V6]
Source Right Ascension (J2000 degrees) (0:360) [] 193.98
Source Declination (J2000 degrees) (-90:90) [] -5.82
minimum energy (MeV)[20.] 100
maximum energy (MeV)[2e5] 100000
number of energies[20]
maximum angle (degrees)[30.]
number of angles[300]
That last example could be also run in the command line as follows:
>gtpsf expcube=expCube.fits outfile=psf.fits irfs=P7SOURCE_V6 ra=193.98 \
dec=-5.82 emin=100.0 emax=100000.0 nenergies=20 thetamax=30 ntheta=300
LIST OF BUGS
SEE ALSO
gtltcube