GeV emission in the region of Vela: A new view of the supernova remnant

The Vela supernova remnant (SNR), G263.9-3.3, and its pulsar wind nebula (PWN), Vela X, is one of the closest such systems, and it has been studied using observations across the electromagnetic spectrum. The SNRs are known sources of gamma rays with energies from the GeV to TeV range. In the GeV band, a cluster of catalogued unidentified -LAT point sources are found across the large angular extension of the Vela SNR. Fermi We aim to search for a high-energy signature associated with the SNR. We applied two independent machine-learning algorithms to classify unidentified point sources in the Vela region by comparing their properties to those of known populations of pulsars and active galactic nuclei. We analysed LAT data and modelled the spectrum of any emission attributable to Vela using leptonic and hadronic processes typical of SNRs. Fermi We find that most of the 'point sources' catalogued within the extent of Vela do not share characteristics with those of the two most common point-like source populations and that even after the emission attributed to these point sources is subtracted, considerable residual emission is seen throughout Vela. Morphologically, most of the GeV emission is found within the shell of the SNR. We conclude that the majority of the catalogued point sources are likely spurious, and the GeV gamma rays come from an extended source, which we argue is the counterpart of the Vela SNR. Adopting a simple morphology given by a uniform disk for the emission, the resulting extension is ∼ 6.5^̧irc. The northeastern portion of G263.9-3.3, where the ambient density is thought to be higher, is brighter in gamma rays than the southern and western regions. The spectrum of the emission is best fit with a hadronic model. These facts make the hadronic origin of the gamma rays more likely. Fermi