Probing the sea of galactic cosmic rays with Fermi-LAT

Aharonian, F.; Peron, Giada; Yang, R.; Casanova, S.; Zanin, R.

doi:10.1103/physrevd.101.083018

Cited by 56 publications

(89 citation statements)

References 46 publications

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“…As can be seen from Figure 2, the γ-ray spectrum of Taurus coincides with the AMS-02-based γ-ray spectrum as already reported by several authors (Yang et al 2014;Aharonian et al 2020). However, in the case of Orion A and Orion B, there is a minor γ-ray excess as also reported by Yang et al (2014) in the lower energies.…”

Section: Resultssupporting

confidence: 86%

Evidence of Cosmic-Ray Excess from Local Giant Molecular Clouds

Baghmanyan

Peron

Casanova

et al. 2020

ApJL

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We report the analysis of the Fermi-Large Area Telescope data from six nearby giant molecular clouds (MCs) belonging to the Gould Belt and the Aquila Rift regions. The high statistical γ-ray spectra above 3 GeV well described by power laws make it possible to derive precise estimates of the cosmic-ray (CR) distribution in the MCs. The comparison of γ-ray spectra of Taurus, Orion A, and Orion B clouds with the model expected from Alpha Magnetic Spectrometer (AMS-02) CR measurements confirms these clouds as passive clouds, immersed in an AMS-02-like CR spectrum. A similar comparison of Aquila Rift, Rho Oph, and Cepheus spectra yields significant deviation in both spectral indices and absolute fluxes, which can imply an additional acceleration of CRs throughout the entire clouds. Besides, the theoretical modeling of the excess γ-ray spectrum of these clouds, assuming π 0-decay interaction of CRs in the cloud, gives a considerable amount of an enhanced CR energy density and it shows a significant deviation in spectral shapes compared to the average AMS-02 CR spectrum between 30 GeV and 10 TeV. We suggest that this variation in the CR spectrum of Cepheus could be accounted for by an efficient acceleration in the shocks of winds of OB associations, while in Rho Oph, similar acceleration can be provided by multiple T-Tauri stars populated in the whole cloud. In the case of Aquila Rift, the excess in absolute CR flux could be related to an additional acceleration of CRs by supernova remnants or propagation effects in the cloud.

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Section: Resultssupporting

confidence: 86%

Evidence of Cosmic-Ray Excess from Local Giant Molecular Clouds

Baghmanyan

Peron

Casanova

et al. 2020

ApJL

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“…Note, however, that these results were challenged recently by Ref. [192] which finds a rather homogeneous CR sea below 100 GeV.…”

Section: Primary Cosmic Ray Nucleimentioning

confidence: 89%

Cosmic ray models

Kachelrieß

Semikoz

2019

Progress in Particle and Nuclear Physics

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We review progress in high-energy cosmic ray physics focusing on recent experimental results and models developed for their interpretation. Emphasis is put on the propagation of charged cosmic rays, covering the whole range from ∼ (20 − 50) GV, i.e. the rigidity when solar modulations can be neglected, up to the highest energies observed. We discuss models aiming to explain the anomalies in Galactic cosmic rays, the knee, and the transition from Galactic to extragalactic cosmic rays.

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“…In the standard diffusion picture it is assumed that Galactic CRs form a smooth, stationary "sea" around the Galactic disk. Evidence for this assumption comes from γ-ray observations, which indicate a rather small variation of the parent CR populations below ≈ 100 GeV throughout the Galaxy outside of several kpc from the Galactic center [50]. Going to higher energies, CRs escape faster and thus the number of CR sources contributing to the local flux diminishes.…”

Section: Discussionmentioning

confidence: 99%

Vela as the source of Galactic cosmic rays above 100 TeV

Bouyahiaoui

Kachelrieß

Semikoz

2019

J. Cosmol. Astropart. Phys.

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We model the contribution of the nearest young supernova remannt Vela to the local cosmic ray flux taking into account both the influence of the Local Superbubble and the effect of anisotropic diffusion. The dominant contribution of this source in the energy region around the cosmic ray knee can naturally explain the observed fluxes of individual groups of nuclei and their total flux. Adding the CR flux from a 2-3 Myr old local CR source suggested earlier, the CR spectra in the whole energy range between 200 GeV and the transition to extragalactic CRs are described well by the combined fluxes from these two local Galactic sources.Keywords: High energy cosmic rays, Vela supernova remnant, Local Superbubble, Galactic magnetic field.The measured energy spectrum of cosmic rays (CRs) extends smoothly over more than 11 decades as a nearly featureless power law, I(E) ∝ E −β . One of its most prominent features is the knee, a break in the all-particle energy spectrum at the energy E k 4 PeV, which was discovered by Kulikov and Khristiansen in the data of the MSU experiment already in 1958 [1]. The second knee corresponds to a change in the spectral slope of the all-particle energy spectrum at 5 × 10 17 eV where the slope hardens by ∆β 0.2. There is a general consensus that the knee in the total CR spectrum at E k 4 PeV coincides with a suppression of the primary proton and/or helium flux, and that the composition becomes increasingly heavier in the energy range between the knee and 10 17 eV [2][3][4][5].Explanations for the origin of the knee fall in two main categories, connecting it either with a change in the propagation or the injection of CRs. In the first case, the knee energy may either corresponds to the rigidity at which the CR Larmor radius R L is of the order of the coherence length l c of the turbulent magnetic field in the Galactic disk [6,7]. Alternatively, the knee corresponds to a transition between the dominance of pitch angle scattering to Hall diffusion or drift along the regular field [8][9][10]. In both cases, the energy dependence of the confinement time changes which in turn induces a steepening of the CR spectrum [6][7][8][9][10][11]. In the second class of models, the knee is connected to properties in the injection spectrum of the Galactic CR sources. For instance, the knee might correspond to the maximal rigidity to which CRs can be accelerated by the population of Galactic CR sources dominating the CR flux below PeV [12][13][14]. Alternatively, the knee may be caused by a break in the source CR energy spectrum at this rigidity [15,16]. A variant of this model is the suggestion that the spectrum below the knee is dominated by a single, nearby source and that the knee correspond to the maximal energy of this specific source [17,18]. All these models lead to a sequence of knees at ZE k , a behaviour first suggested by Peters [19].In the isotropic diffusion approximation one defines a scalar diffusion coefficient which depends on energy as D(E) = D 0 (E/E 0 ) δ . Measurements of the Boron and Carb...

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Probing the sea of galactic cosmic rays with Fermi-LAT

Cited by 56 publications

References 46 publications

Evidence of Cosmic-Ray Excess from Local Giant Molecular Clouds

Evidence of Cosmic-Ray Excess from Local Giant Molecular Clouds

Cosmic ray models

Vela as the source of Galactic cosmic rays above 100 TeV

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