The status of H.E.S.S. and CTA, and their role in a multiwavelength context

Abstract

The High Energy Stereoscopic System (H.E.S.S.) is a world-class experiment located in Namibia and consists of an array of four 13-m telescopes which investigate the non-thermal universe in the 100 GeV to 100 TeV energy range via the Cherenkov technique. H.E.S.S. is sensitive to fluxes of a few thousandths of that of the Crab Nebula, has a wide field of view (FoV; 5°), sub-degree angular resolution (<0.1°), accurate pointing (< 1000), and good spectral resolution (10−20%). Its excellent location affords a clear view of the Galactic Centre as well as many Galactic sources. H.E.S.S. Phase II, entailing the addition of a 28-m central telescope to the existing four, is already underway. This will result in increased energy coverage (with an expected threshold of ~20 GeV), sensitivity, and angular resolution. Efforts towards the design and construction of a next-generation gamma-ray observatory called the Cherenkov Telescope Array (CTA) are gaining momentum. This will consist of a northern and southern component, unifying the global gamma-ray astronomy community, and will boast an order-of-magnitude increase in sensitivity. The status of the Southern African site bid for hosting CTA-South is discussed. Lastly, it is important to view our knowledge of the very-high-energy (VHE) sky within the greater multiwavelength context, it being complementary to observations at lower energies (e.g., high-energy gamma rays, X-rays, optical, and radio waves). The rich opportunities created by such a synergy will bolster the continued study of some of the most violent and energetic phenomena in the Universe.