Prerequisite Science Tools: UnbinnedAnalysis

Note: Steps 1 and 2, enable you to eliminate photons coming from the Earth limb by applying a zenith angle cut of 105^o; gtmktime also updates the Good Time Intervals (GTIs) to match the FT2 data.

For a more detailed discussion, see Agreed procedures for data preparation: Removing Earth's Albedo and Correcting GTIs.

Create an exposure cube (using gtltcube).

Note: gtltcube outputs an expCube.fits file, a HealPix table covering the full sky of the integrated livetime as a function.

Create an exposure map (using gtexpmap).

Create a source model XML file (using the Astro Data Viewer tool and the diffuse model recommend by the Diffuse Science Group).

1. Run gtselect

Refer to: gtselect.

Run gtselect as follows:

bash-3.2$ gtselect
Input FT1 file[pyLike-ft1.fits]
Output FT1 file[3C454-ft1.fits]
RA for new search center (degrees) (0:360) [180] 343.6566
Dec for new search center (degrees) (-90:90) [0] 16.1494
radius of new search region (degrees) (0:180) [15]
start time (MET in s) (0:) [243756000]
end time (MET in s) (0:) [243842400]
lower energy limit (MeV) (0:) [100]
upper energy limit (MeV) (0:) [300000]
maximum zenith angle value (degrees) (0:180) [105]
Done.
bash-3.2$

Note: Since we obtained our data from the Astro Data server and are only running gtselect to filter out any data greater than 105^o, the maximum zenith angle, we could simply enter: Input FT1 file; Output FT1 file; radius of the new search region [180]; and maximum zenith angle value [105].

Verify that the output file is now in your work directory.

2. Select GTIs (using gtmktime)

Refer to: gtmktime and and gtvcut

bash-3.2$ gtmktime
Spacecraft data file[pyLike-ft2-30s.fits]
Filter expression[Filter expression[(DATA_QUAL==1 && LAT_CONFIG==1 && ABS(ROCK_ANGLE)<52)]]
Apply ROI-based zenith angle cut[yes]
Event data file[3C454-ft1.fits]
Output event file name[3C454_back-filtered.fits]

Tip: Use gtvcut if you wish to view the Data SubSpace Keywords. (See gtvcut Help file; also see Data SubSpace Keywords.

3. Create Exposure Cube (using gtltcube)

Refer to: gtltcube

Run gtltcube.

bash-3.2$ gtltcube
Event data file[3C454_back-filtered.fits]
Spacecraft data file[pyLike-ft2-30s.fits]
Output file[3C454-expCube.fits]
Step size in cos(theta) (0.:1.) [0.025]
Pixel size (degrees)[1]
Working on file pyLike-ft2.fits
.....................!
bash-3.2$

Verify that the output file is now in your work directory.

4. Create Exposure Map (using gtexpmap)

Refer to: gtexpmap

Run gtexpmap.

bash-3.2$ gtexpmap
The exposure maps generated by this tool are meant to be used for *unbinned* likelihood analysis only. Do not use them for binned analyses.
Event data file[3C454_back-filtered.fits]
Spacecraft data file[pyLike-ft2-30s.fits]
Exposure hypercube file[3C454-expCube.fits]
output file name[3C454-expMap.fits]
Response functions[P6_V3_DIFFUSE]
Radius of the source region (in degrees)[25]
Number of longitude points (2:1000) [120]
Number of latitude points (2:1000) [120]
Number of energies (2:100) [10]
Computing the ExposureMap using 3C454-expCube.fits
....................!
bash-3.2$

Note the warning message stating that the "exposure maps generated by this tool are meant to be used for *unbinned* likelihood analysis only. Do not use them for binned analyses".

Verify that the output file is now in your work directory.

5. Create a Source Model XML File

Create a Source Model XML File (using Astro Data Viewer).

Copy your XML source model file to your work directory on SLAC Public.

You are now ready to perform an unbinned pyLikelihood analysis; see pyLikelihood: UnbinnedAnalysis.

Note: Since we obtained our data from the Astro Server, the gtdiffrsp function for point sources has already been performed during L1 processing; hence, it is no longer necessary to run gtdiffrsp before performing an analysis of point sources. (See gtdiffrsp Help File.)

Owned by: Jim Chiang

Last updated by: Chuck Patterson 04/01/2011

04/01/2011