Galactic cosmic rays reach energies of at least a few Peta-electronvolts (1 PeV =1015 electron volts)1 . This implies our Galaxy contains PeV accelerators (PeVatrons), but all proposed models of Galactic cosmic-ray accelerators encounter non-trivial difficulties at exactly these energies 2 . Tens of Galactic accelerators capable of accelerating particle to tens of TeV (1 TeV =10 12 electron volts) energies were inferred from recent gamma-ray observations 3 . None of the currently known accelerators, however, not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays, have shown the characteristic tracers of PeV particles: power-law spectra of gamma rays extending without a cutoff or a spectral break to tens of TeV 4 . Here we report deep gamma-ray observations with arcminute angular resolution of the Galactic Centre regions, which show the expected tracer of the presence of PeV particles within the central 10 parsec of the Galaxy. We argue that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts 5 and an outflow from the Galactic Center 6 . Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 10 6−7 years, and therefore should be considered as a viable alternative to supernova remnants as a source of PeV Galactic cosmic rays.The large photon statistics accumulated over the last 10 years of observations with the High Energy Stereoscopic System (H.E.S.S.), together with improvements in the methods of data analysis, allow for a deep study of the properties of the diffuse very-high-energy (VHE; more than 100 GeV) emission of the central molecular zone. This region surrounding the Galactic Centre contains predominantly molecular gas and extends (in projection) out to r∼250 pc at positive galactic longitudes and r∼150 pc at negative longitudes. The map of the central molecular zone as seen in VHE γ-rays (Fig. 1) shows a strong (although not linear; see below) correlation between the brightness distribution of VHE γ-rays and the locations of massive gas-rich complexes. This points towards a hadronic origin of the diffuse emission 7 , where the γ-rays result from the interactions of relativistic protons with the ambient gas. The second important mechanism of production of VHE γ-rays 3 is the inverse Compton scattering of electrons. However, the severe radiative losses suffered by multi-TeV electrons in the Galactic Centre region prevent them from propagating over scales comparable to the size of the central molecular zone, thus disfavouring a leptonic origin of the γ-rays (see discussion in Methods and Extended Data Figures 1 and 2). The location and the particle injection rate history of the cosmic-ray accelerator(s), responsible for the relativistic protons, determine the spatial distribution of these cosmic rays which...

Context. Jets from rotation-powered pulsars so far have only been observed in systems moving subsonically through their ambient medium and/or embedded in their progenitor supernova remnant (SNR). Supersonic runaway pulsars are also expected to produce jets, but they have not been confirmed so far. Aims. We investigated the nature of the jet-like structure associated with the INTEGRAL source IGR J11014-6103 (the "Lighthouse nebula"). The source is a neutron star escaping its parent SNR MSH 11-61A supersonically at a velocity exceeding 1000 km s −1 . Methods. We observed the Lighthouse nebula and its jet-like X-ray structure through dedicated high spatial resolution observations in X-rays (with Chandra) and in the radio band (with ATCA). Results. Our results show that the feature is a true pulsar's jet. It extends highly collimated over 11pc, displays a clear precessionlike modulation, and propagates nearly perpendicular to the system direction of motion, implying that the neutron star's spin axis in IGR J11014-6103 is almost perpendicular to the direction of the kick received during the supernova explosion. Conclusions. Our findings suggest that jets are common to rotation-powered pulsars, and demonstrate that supernovae can impart high kick velocities to misaligned spinning neutron stars, possibly through distinct, exotic, core-collapse mechanisms.

Aims. Results obtained in very-high-energy (VHE; E ≥ 100 GeV) γ-ray observations performed with the H.E.S.S. telescope array are used to investigate particle acceleration processes in the vicinity of the young massive stellar cluster Westerlund 1 (Wd 1). Methods. Imaging of Cherenkov light from γ-ray induced particle cascades in the Earth's atmosphere is used to search for VHE γ rays from the region around Wd 1. Possible catalogued counterparts are searched for and discussed in terms of morphology and energetics of the H.E.S.S. source. Results. The detection of the degree-scale extended VHE γ-ray source HESS J1646-458 is reported based on 45 h of H.E.S.S. observations performed between 2004 and 2008. The VHE γ-ray source is centred on the nominal position of Wd 1 and detected with a total statistical significance of ∼20σ. The emission region clearly extends beyond the H.E.S.S. point-spread function (PSF). The differential energy spectrum follows a power law in energy with an index of Γ = 2.19 ± 0.08 stat ± 0.20 sys and a flux normalisation at 1 TeV of Φ 0 = (9.0 ± 1.4 stat ± 1.8 sys ) × 10 −12 TeV −1 cm −2 s −1 . The integral flux above 0.2 TeV amounts to (5.2 ± 0.9) × 10 −11 cm −2 s −1 . Conclusions. Four objects coincident with HESS J1646-458 are discussed in the search of a counterpart, namely the magnetar CXOU J164710.2−455216, the X-ray binary 4U 1642-45, the pulsar PSR J1648-4611 and the massive stellar cluster Wd 1. In a single-source scenario, Wd 1 is favoured as site of VHE particle acceleration. Here, a hadronic parent population would be accelerated within the stellar cluster. Beside this, there is evidence for a multi-source origin, where a scenario involving PSR J1648-4611 could be viable to explain parts of the VHE γ-ray emission of HESS J1646-458.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. An annihilation signal of dark matter is searched for from the central region of the Milky Way. Data acquired in dedicated on-off observations of the Galactic center region with H.E.S.S. are analyzed for this purpose. No significant signal is found in a total of ∼9 h of on-off observations. Upper limits on the velocity averaged cross section, hσvi, for the annihilation of dark matter particles with masses in the range of ∼300 GeV to ∼10 TeV are derived. In contrast to previous constraints derived from observations of the Galactic center region, the constraints that are derived here apply also under the assumption of a central core of constant dark matter density around the center of the Galaxy. Values of hσvi that are larger than 3 × 10 −24 cm 3 =s are excluded for dark matter particles with masses between ∼1 and ∼4 TeV at 95% C.L. if the radius of the central dark matter density core does not exceed 500 pc. This is the strongest constraint that is derived on hσvi for annihilating TeV mass dark matter without the assumption of a centrally cusped dark matter density distribution in the search region. Introduction.-The formation of the large scale structure of the universe as well as the dynamics of galaxy clusters and individual galaxies strongly suggest the presence of dark matter on the respective length scale [1]. Many extensions of the standard model of particle physics predict a stable particle without electromagnetic coupling whose presence can account for the missing mass that is apparent in astrophysical environments [1]. The annihilation of dark matter particles is expected to produce photons with energies up to the mass of the dark matter particles [2]. The detection of γ rays from a given direction can thus indirectly probe the presence of dark matter particles along the corresponding line of sight.The central region of the Milky Way is of particular interest for indirect searches for annihilating dark matter because the squared dark matter density integrated over the line of sight towards the target region (i.e., the astrophysical or J factor) is expected to be large [3]. The J factor for observations of the Galactic center region depends strongly on the dark matter density distribution within the Milky Way. Simulations of the dynamics of the dark matter content of galaxies predict to universal dark matter density distributions. Towards the center of the galaxies, the influence of baryons on the distribution of dark matter is not yet resolved. The formation of pronounced den...