Measurement of the Fermi-LAT Localization Performance

Understand

We present results of a study of the localization capability of Fermi-LAT, using a large set of blazars with precise radio locations.

• Since the width of the PSF decreases with energy, the performance is typically dominated by a few high energy photons, so it is important to properly characterize the high-energy PSF.
• Using such data, we have found a need to modify the pre-launch high-energy (greater than a few GeV) PSF derived from extensive Monte Carlo simulations of particle interactions in the LAT; the resulting data-based PSF is shown