Origin of cosmic rays excess in the Galactic Center

Jouvin, L.; Lemière, A.; Terrier, R.

doi:10.22323/1.236.0918

Cited by 2 publications

(2 citation statements)

References 17 publications

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“…For the spectral analysis, the background is estimated using the reflected region method (Berge et al 2007), where the background is derived from circular off−source regions with the same angular size and γ-ray detection efficiency as the on−source region. The differential VHE γ-ray spectrum is then fitted with a spectral model by forward folding it with the instrument response functions (Piron et al 2001;Jouvin et al 2015).…”

Section: Hess Observations and Data Analysismentioning

confidence: 99%

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

Abdalla

Abramowski

Aharonian

et al. 2018

A&A

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The diffuse very high−energy (VHE, > 100 GeV) γ-ray emission observed in the central 200 pc of the Milky Way by H.E.S.S. was found to follow the 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 10 4 years 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 γ-ray sources in the inner 200 pc. Taking advantage of 250 hours 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 γ-ray emission, we use 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 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 the full ridge diffuse emission is compatible with the one 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 γ-ray source near the GC radio arc and argue that it is produced by the pulsar wind nebula candidate G0.13−0.11.

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Section: Hess Observations and Data Analysismentioning

confidence: 99%

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

Abdalla

Abramowski

Aharonian

et al. 2018

A&A

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“…This assumption is for the first approximation reasonable as until R ≈ 200 pc the spiral arms are not characterized. Moreover, as the advection speed is not competitive with diffusion following to [7], this process is neglected in our calculations. These settings lead to the following transport equation…”

Section: Modelmentioning

confidence: 99%

A Novel Analytical Model of the Magnetic Field Configuration in the Galactic Center Explaining the Diffuse Gamma-Ray Emission (ICRC-2019)

Guenduez¹,

Tjus²,

Ferrière³

et al. 2019

Preprint

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Reliable identification of the origin of the high-energy non-thermal emission from the Galactic Center (GC) is not achievable without adequate consideration of the ambient conditions such as the magnetic field configuration or gas distribution. In a first step, we present a model that can explain the diffuse gamma-ray emission as measured by H.E.S.S. for small longitudes in the Galactic Center region but comes to grief with higher longitudes. The model is given via the solution of a transport equation that allows for a radial dependency of the mass distribution. In order to move from this semi-analytical approximation toward a full understanding of the PeVatron signature, we present a new 3D analytical model of the gas distribution in the Central Molecular Zone (CMZ). Furthermore, we derive for the first time a 3D model of the magnetic field configuration and strength in the CMZ, which is analytical and divergence-free. The model is built via a combination of a model for the diffuse inter-cloud medium, local molecular clouds and nonthermal filaments at which local information are based on investigations from previous works and the molecular gas density. It can be shown that without an efficient longitudinal CR entrapment, a single source at the center does not facilely suffice the diffuse gamma-ray detection. Further, we show that the new magnetic field model GBFD19 is compatible with recent polarization data and has a significant impact on the longitudinal profiles of CR propagation.

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Origin of cosmic rays excess in the Galactic Center

Cited by 2 publications

References 17 publications

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

Characterising the VHE diffuse emission in the central 200 parsecs of our Galaxy with H.E.S.S.

A Novel Analytical Model of the Magnetic Field Configuration in the Galactic Center Explaining the Diffuse Gamma-Ray Emission (ICRC-2019)

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