2. Image

2.1. Intro

high-energy all-sky count map; look at Fermi bubbles and maybe other sources using 2FGL region file (gtbin, ds9)

2.2. Prepare the data

The following procedure is explained in Getting Started.

You start by creating a file events.txt that contains the photon data files you downloaded. Note that in this case there the Fermi LAT data server generated eight files, each only about 1 MB (mega-byte) large because there are only few events above 10 GeV.:

$ ls -1 *_PH??.fits > events.txt
$ du -hs *_PH??.fits
968K  L1309071835220B976F4330_PH00.fits
1004K L1309071835220B976F4330_PH01.fits
1.1M  L1309071835220B976F4330_PH02.fits
1.2M  L1309071835220B976F4330_PH03.fits
1.0M  L1309071835220B976F4330_PH04.fits
1.1M  L1309071835220B976F4330_PH05.fits
1.0M  L1309071835220B976F4330_PH06.fits
840K  L1309071835220B976F4330_PH07.fits
808K  L1309071835220B976F4330_PH08.fits

Now tun the following commands in sequence. gtselect will just take a few seconds, gtmktime a few minutes and gtltcube will take a few hours ... so we suggest you copy the file gtltcube.fits from the solutions folder so that you can continue quickly

$ gtselect infile=@events.txt outfile=gtselect.fits \
  ra=INDEF dec=INDEF rad=INDEF tmin=INDEF tmax=INDEF \
  emin=10000 emax=1000000 zmax=100 evclass=2

$ gtmktime scfile=../spacecraft.fits evfile=gtselect.fits \
  filter=DATA_QUAL==1&&LAT_CONFIG==1&&ABS(ROCK_ANGLE)<52 \
  roicut=yes outfile=gtmktime.fits

$ gtltcube evfile=gtmktime.fits scfile=../spacecraft.fits \
  outfile=gtltcube.fits dcostheta=0.025 binsz=1

2.3. Make a count cube and image

gtbin ds9

2.4. Compute an exposure cube

gtexpcube2

2.5. Compute a diffuse model image

gtsrcmaps

2.6. Compute an excess and significance image

TODO: Give a Python script to do it (tophat-correlate or PSF-correlate, then apply LiMa formula).

2.7. A quick look at a few sources

TODO: Overplot 2FGL and 1HFL catalogs as well as TeVCAT and Green and ATNF in Aladin.

  • HESS J1825
  • RX J1713
  • Galactic center