Sharper Fermi LAT Images: instrument response functions for an improved event selection

Abstract

The Large Area Telescope on the Fermi Gamma-ray Space Telescope has a point spread function with large tails, consisting of events affected by tracker ineffiencies, inactive volumes, and hard scattering; these tails can make source confusion a limiting factor. The parameter CTBCORE, available in the publicly available Extended Fermi LAT data, estimates the quality of each event's direction reconstruction; by implementing a cut in this parameter, the tails of the point spread function can be suppressed at the cost of losing effective area. We implement cuts on CTBCORE and present updated instrument response functions derived from the Fermi LAT data itself, along with all-sky maps generated with these cuts. Having shown the effectiveness of these cuts, especially at low energies, we encourage their use in analyses where angular resolution is more important than Poisson noise.

arXiv comment6 pages, 6 figures; extended PSF analysis down to 100 MeV, typos corrected; to be published in The Astrophysical Journal

References in corpus (4)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Fermi Large Area Telescope On Orbit: Event Classification, Instrument Response Functions, and Calibration
• Fermi-LAT Search for Pulsar Wind Nebulae around gamma-ray Pulsars
• Determination of the Point-Spread Function for the Fermi Large Area Telescope from On-orbit Data and Limits on Pair Halos of Active Galactic Nuclei

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