Unveiling TeV halos among unidentified extended TeV sources

Abstract: In recent years, the number of known sources emitting very- and ultra-high-energy gamma-rays has increased significantly thanks to facilities such as LHAASO and HAWC. Many of the observed sources are still unidentified or poorly constrained due to the limited angular resolution of these instruments; however, it is now ascertained that approximately half of them have a pulsar in coincidence. Some of these unidentified extended sources may be the result of the diffusion of leptons accelerated by the pulsar itself or in its nebula to energies exceeding 50 TeV. This new class of sources, called TeV halos, is characterized by a peculiar radial profile that, if properly resolved, is key to distinguishing them from other TeV sources that are associated with a pulsar, such as supernova remnants and pulsar wind nebulae. In this contribution, we consider all the pulsars which are spatially coincident with an unidentified extended TeV source, in order to quantify whether its spin-down power, age and distance allow the pulsar to produce a TeV halo with the observed flux and extension. We also investigate how the next generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), namely the Cherenkov Telescope Array Observatory (CTAO) and the ASTRI Mini-Array, will observe and characterize these TeV halos. We present a set of simulated sources with the expected morphology and spectrum, and we show for which of them we can distinguish between TeV halos and other classes of extended sources.