C.D.S. - SIMBAD4 rel 1.7 - 2020.07.03CEST22:49:57

2017A&A...606A..22N - Astronomy and Astrophysics, volume 606A, 22-22 (2017/10-1)

Cosmic-ray spectrum in the local Galaxy.


Abstract (from CDS):

Aims. We study the spectral properties of the cosmic-ray spectrum in the interstellar medium within 1 kpc distance from the Sun.
Methods. We used eight-year exposure data of molecular clouds of the Gould Belt obtained with the Fermi-LAT telescope to precisely measure the cosmic-ray spectrum at different locations in the local Galaxy. We compared this measurement with the direct measurements of the cosmic-ray flux in and around the solar system obtained by Voyager and AMS-02 or PAMELA.
Results. We find that the average cosmic-ray spectrum in the local Galaxy in the 1-100GeV range is well described by a broken power-law in rigidity with a low-energy slope of 2.33+0.06–0.08 and a break at 18+7–4GV, with a slope change by 0.59±0.11. This result is consistent with an earlier analysis of the γ-ray signal from the Gould Belt clouds based on a shorter exposure of Fermi-LAT and with a different event selection. The break at 10-20GV is also consistent with the combined Voyager + AMS-02 measurements in/around the solar system. The slope of the spectrum below the break agrees with the slope of the average cosmic-ray spectrum in the inner part of the disk of the Milky Way that was previously derived from the Fermi-LAT γ-ray data. We conjecture that it is this slope of 2.33 and not the locally measured softer slope of 2.7-2.8 that is determined by the balance between a steady-state injection of cosmic rays with a power-law slope of 2-2.1 that is due to Fermi acceleration and the energy-dependent propagation of cosmic-ray particles through the turbulent interstellar magnetic field with a Kolmogorov turbulence spectrum. The approximation of a continuous-in-time injection of cosmic rays at a constant rate breaks down, which causes the softening of the spectrum at higher energies.

Abstract Copyright: © ESO, 2017

Journal keyword(s): ISM: clouds - cosmic rays - local insterstellar matter - gamma rays: ISM - gamma rays: ISM

Simbad objects: 9

goto Full paper

goto View the reference in ADS

Number of rows : 9

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 NAME Perseus Cloud SFR 03 35.0 +31 13           ~ 1061 0
2 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3478 0
3 NAME Ori A MoC 05 38 -07.1           ~ 2675 0
4 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1164 0
5 NAME Mon R2 HII 06 07 46.6 -06 22 59           ~ 650 2
6 NAME Cha Dark Cloud SFR 11 55 -78.0           ~ 556 1
7 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3027 0
8 NAME CrA Dark Cloud MoC 19 01 51 -36 58.9           ~ 394 0
9 NAME Cep Cloud SFR 22 00.0 +76 30           ~ 99 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2017A&A...606A..22N and select 'bookmark this link' or equivalent in the popup menu


© Université de Strasbourg/CNRS

    • Contact