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Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with HESS
North-West University, South Africa.
University of Hamburg, Germany.
Max Planck Institute for Nuclear Physics, Germany ; Dublin Institute for Advanced Studies, Ireland ; National Academy of Sciences of the Republic of Armenia, Armenia.
Max Planck Institute for Nuclear Physics, Germany.
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2018 (Engelska)Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 612, artikel-id A9Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The diffuse very high-energy (VHE; > 100 GeV) gamma-ray emission observed in the central 200 pc of the Milky Way by H.E.S.S. was found to follow dense matter distribution in the central molecular zone (CMZ) up to a longitudinal distance of about 130 pc to the Galactic centre (GC), where the flux rapidly decreases. This was initially interpreted as the result of a burst-like injection of energetic particles 104 yr ago, but a recent more sensitive H.E.S.S. analysis revealed that the cosmic-ray (CR) density profile drops with the distance to the centre, making data compatible with a steady cosmic PeVatron at the GC. In this paper, we extend this analysis to obtain, for the first time, a detailed characterisation of the correlation with matter and to search for additional features and individual gamma-ray sources in the inner 200 pc. Taking advantage of 250 h of H.E.S.S. data and improved analysis techniques, we perform a detailed morphology study of the diffuse VHE emission observed from the GC ridge and reconstruct its total spectrum. To test the various contributions to the total gamma-ray emission, we used an iterative 2D maximum-likelihood approach that allows us to build a phenomenological model of the emission by summing a number of different spatial components. We show that the emission correlated with dense matter covers the full CMZ and that its flux is about half the total diffuse emission flux. We also detect some emission at higher latitude that is likely produced by hadronic collisions of CRs in less dense regions of the GC interstellar medium. We detect an additional emission component centred on the GC and extending over about 15 pc that is consistent with the existence of a strong CR density gradient and confirms the presence of a CR accelerator at the very centre of our Galaxy. We show that the spectrum of full ridge diffuse emission is compatible with that previously derived from the central regions, suggesting that a single population of particles fills the entire CMZ. Finally, we report the discovery of a VHE gamma-ray source near the GC radio arc and argue that it is produced by the pulsar wind nebula candidate G0.13-0.11.

Ort, förlag, år, upplaga, sidor
EDP Sciences, 2018. Vol. 612, artikel-id A9
Nyckelord [en]
gamma rays: general, gamma rays: ISM, Galaxy: center, cosmic rays
Nationell ämneskategori
Astronomi, astrofysik och kosmologi
Forskningsämne
Fysik, Astropartikelfysik
Identifikatorer
URN: urn:nbn:se:lnu:diva-76467DOI: 10.1051/0004-6361/201730824ISI: 000429404700009Scopus ID: 2-s2.0-85045525369OAI: oai:DiVA.org:lnu-76467DiVA, id: diva2:1232114
Tillgänglig från: 2018-07-10 Skapad: 2018-07-10 Senast uppdaterad: 2019-08-29Bibliografiskt granskad

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Becherini, YvonneFarnier, ChristianProkhorov, DmitryPunch, Michael

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