Are GeV and TeV spectra connected? the case of Galactic gamma-ray sources

TL;DR

This study investigates the spectral connection between GeV and TeV gamma-ray sources in the Galaxy, revealing that many sources emit across both bands but often cannot be described by a single spectral component, indicating complex emission mechanisms.

Contribution

It extends previous correlation studies by analyzing the first Fermi catalog with VHE sources, highlighting the spectral complexity of coincident sources.

Findings

Many VHE sources are also detected in the GeV band.

Some GeV-TeV sources cannot be modeled by a single spectral component.

Spectral complexity suggests diverse emission mechanisms.

Abstract

To understand Galactic objects that emits GeV-TeV emission, a spatial correlation study between the Fermi bright source catalog and TeV source population was carried out in Tam et al. (2010), finding that a significant number of very high-energy (VHE; E >100 GeV) sources are also emitting at GeV energies. We extended our previous study utilizing the first Fermi catalog (1FGL) sources. A cross-correlation comparison of the 1FGL sources was carried out with the VHE gamma-ray sources in the literature as of May 2011. While it is found that a significant number of VHE gamma-ray sources were also detected in the GeV band, the GeV-TeV spectra of some of these spatially coincident sources cannot be described by a single spectral component. While some of these cases are gamma-ray pulsars accompanied by VHE gamma-ray emitting nebulae, we present cases where the 100 MeV to multi-TeV spectra of coincident 1FGL/VHE source pairs do not seem to be well fit by a single spectral component.