Narrow Results

H.E.S.S. is an experiment for ground based GeV/TeV gamma ray astronomy of the new generation. It consists of four large Cherenkov telescopes operating in stereoscopic observation mode. Its construction in Namibia was completed at the end of 2003. Already during the installation phase, exciting results have been achieved, and after completion several discoveries have been made. Some of the results and discoveries are reported, such as the first image of a shell-type supernova remnant resolved at arc minute scale (RXJ 1713 – 3946), the discovery of the unique binary pulsar system PSR B1259 – 63 and of a yet-unidentified source in the same field of view (HESS J1303 – 631), and the observation of the galactic centre region. Amongst the extragalactic sources, the blazers Mkn 421 and PKS 2155 – 304 have also been detected.

Here we discuss two related aspects of the detection of low energy gammas by IACT's (Imaging Atmospheric Cherenkov Telescope): the effect of the Earth's magnetic field and a possible novel trigger technique. The Earth's magnetic field affects the development of extensive air showers (EAS), spreading the collected photons and, therefore, decreasing the sensitivity of the Cherenkov telescope. The new effects that appear in low energy showers can be partially offset modifying the trigger criteria. The result is a large collection area (> 1000 m²) below 10 GeV for a typical 17 m class telescope, increasing its sensitivity at these energies.

VERITAS (Very Energetic Radiation Imaging Telescope Array System), an array of ground-based gamma-ray telescopes in southern Arizona, USA, has been taking data in hardware stereo mode since March, 2006. The April–May 2006 dark run provided a large set of data from two telescopes on the known blazar Markarian (Mrk) 421. An initial analysis produced a light curve and preliminary cuts showing the two telescope array's angular resolution to be 0.19°. The remaining two VERITAS telescopes will be brought online by January, 2007.

VERITAS is an atmospheric Cherenkov telescope array sited in Tucson, Arizona. The array is nearing completion and consists of four, 12 m diameter telescopes. The first telescope in the array has been operating since February 2005, while observations with the full array are expected to begin in January, 2007. We report here in some detail on the performance of the first VERITAS telescope, and briefly discuss the first stereo observations.

VERITAS (Very Energetic Radiation Imaging Telescope Array System), an array of ground-based gamma-ray telescopes in southern Arizona, USA, has been taking data in hardware stereo mode since March, 2006. The April–May 2006 dark run provided a large set of data from two telescopes on the known blazar Markarian (Mrk) 421. An initial analysis produced a light curve and preliminary cuts showing the two telescope array's angular resolution to be 0.19°. The remaining two VERITAS telescopes will be brought online by January, 2007.

The annihilations of WIMPs produce high energy gamma-rays in the final state. These high energy gamma-rays may be detected by imaging atmospheric Cherenkov telescopes (IACTs). Amongst the plausible targets are the Galactic Center, the centre of galaxy clusters, dwarf Sphreroidal galaxies and substructures in Galactic haloes. I will review on the recent results from observations of ongoing IACTs.

Annihilations of WIMPs can occur in high density regions of our Galaxy such as the Galactic Centre, dwarf galaxies and other types of substructures in Galactic haloes. High energy gamma-rays can be produced and may be detected by imaging atmospheric Cherenkov telescopes (IACTs). After a short overview of observations with current IACTs, basic principles of indirect detection through gamma-rays are given. Selected results on targeted searches such as satellites galaxies of the Milky Way are shown. In the absence of a clear signal, modelling the dark matter halo profile of these objects allows to put constraints on the particle physics parameters such as the annihilation cross section and the mass of the dark matter particle in the framework of models beyond the Standard Model of Particle Physics. Besides theses searches are wide-field survey searches for DM substructures in the Galactic halo. The case for dark matter spikes around intermediate mass black holes will be discussed. Finally, the next generation of IACTs is presented.