The TeV Sky and Multiwavelength Astrophysics

Abstract

TeV γ-ray astronomy is outside the possibility of space-based experiments and can, at present, only be studied through ground-based experiments. The capability to suppress the high background induced by charged CRs and open the field of TeV γ-ray astronomy was made possible with the advent of the Imaging Air Cherenkov Technique and with some dedicated air shower particle arrays. The online source catalog now contains more than 200 galactic and extragalactic TeV sources. The remarkable achievements of these experiments now include the study of morphology, energy spectrum, and time variability of several galactic and extragalactic source populations. The largest class of galactic TeV emitting sources corresponds to that of pulsars with a wind nebula, among which the Crab is the most studied representative. Shell-type supernova remnants represent the major candidates as galactic sources of CRs, and thus largely studied through GeV-TeV γ-ray observations. Outside the galactic plane, it was discovered that the emission of radiation from jet-dominated AGN covers a large interval of the electromagnetic spectrum and is extremely variable. The coordinated efforts from the community are crucial for a detailed and unbiased study of AGN and other extragalactic objects: multiwavelength searches are becoming more and more important to obtain a complete picture of non-thermal processes in the Universe. Blazars, among the AGN, present some particular features, such as, for example, strong and rapid variability and a jet orientation toward the observer. As these objects are among the furthest observed objects in the Universe, their observation through TeV photons can constraint estimates of the presence of extragalactic background light, which is also relevant for cosmological models.