This will be the sixth edition in a series of Workshops on High Energy Gamma-ray Experiments, following the ones held in Perugia (2003), Bari (2004), Cividale del Friuli (2005), Elba Island (2006) and Villa Mondragone (2007).
This year the focus will be on the region known by the acronym VHE (Very High Energy), bridging the gap between GeV and TeV. The physics that lies in this region is of the utmost importance to improve our knowledge of many different astrophysical sources like pulsars, AGNs, GRBs, and understand the main components of the Extragalactic Background Light (EBL).
An update on the current and planned research for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky will be given. In particular, a special session will be devoted to Fermi.
Among the participants there will be both hardened veterans of the first dedicated gamma-ray missions (like SAS-2, COS-B, CGRO) and young students entering the fascinating field of gamma-ray astrophysics participating in the new generation of dedicated experiments like Fermi, AGILE, MAGIC, HESS, VERITAS, CANGAROO, ARGO and MILAGRO.
Between the higher energies accessible to satellites and the energy threshold of ground based gamma-ray telescopes, a sizeable region of the electromagnetic spectrum, more than a decade wide,remains unexplored.
In this interval, several fundamental problems concerning Astrophysics, Cosmology and Fundamental Physics could find their answers from a thorough astronomical observation.
Cherenkov detectors already caught a few glimpses in this region: the full new wealth of sources in HESS' galactic scan or the discovery by MAGIC of new classes of extragalactic VHE emitters like Flat-Spectrum Radio Quasars (FSRQ) or the Low-frequency BL Lac's type (LBL).
However, the gap will now be covered by the soon to come observations of AGILE and Fermi satellites, sensitive in this region where most of the source cutoffs lie.
This workshop, shortly after Fermi's launch, is one of the first occasions to understand the new opportunities opened by the satellites in orbit, and it is devoted to the sources that will profit more from broad-band (GeV-TeV) observations, possibly giving answers to many astrophysical issues.
Among these there are galactic sources, like pulsars, where a precise measurement of the energy cutoff of the pulsed spectra can discriminate among many competitive acceleration scenarioes. There are also extragalactic sources like active nuclei, where broad-band measurements effectively probe the inner structure of the gravitational engine, or Gamma Ray Bursts (GRBs) where observations by the LAT instrument (on-board the Fermi observatory) may trigger important follow-up with Cherenkov telescopes.
Moreover, the observation of sources located at medium redshift (0.2 < z < 0.5 for Cherenkov and z ~ 1 with Fermi) heavily constrains the EBL, either requiring to refine the evaluation of EBL's components or even to invoke new physics.
The workshop will also introduce the participants to the intricacies of the analysis at very high energies, where data have usually to be mined in a much larger background. Given the presence of many veterans in the field, a special session will be devoted to data analysis and to an overview of the available analysis tools and techniques.