Comparison of Fermi-LAT and CTA in the region between 10-100 GeV

TL;DR

This paper compares the performance of the Fermi-LAT and CTA telescopes in the 10-100 GeV energy range, highlighting their complementarity and implications for gamma-ray source observations.

Contribution

It provides a detailed comparison of Fermi-LAT and CTA capabilities in the 10-100 GeV range, informing optimization strategies for CTA.

Findings

Fermi-LAT and CTA have complementary sensitivities in the 10-100 GeV range.

The overlap region is crucial for source characterization and transient detection.

CTA's design can be optimized considering Fermi-LAT's ongoing data improvements.

Abstract

The past decade has seen a dramatic improvement in the quality of data available at both high (HE: 100 MeV to 100 GeV) and very high (VHE: 100 GeV to 100 TeV) gamma-ray energies. With three years of data from the Fermi Large Area Telescope (LAT) and deep pointed observations with arrays of Cherenkov telescope, continuous spectral coverage from 100 MeV to $\sim10$ TeV exists for the first time for the brightest gamma-ray sources. The Fermi-LAT is likely to continue for several years, resulting in significant improvements in high energy sensitivity. On the same timescale, the Cherenkov Telescope Array (CTA) will be constructed providing unprecedented VHE capabilities. The optimisation of CTA must take into account competition and complementarity with Fermi, in particularly in the overlapping energy range 10$-$100 GeV. Here we compare the performance of Fermi-LAT and the current baseline CTA design for steady and transient, point-like and extended sources.