The Nine Lives of Cosmic Rays in Galaxies

Grenier, I. A.; Black, J. H.; Strong, A. W.

doi:10.1146/annurev-astro-082214-122457

Cited by 314 publications

(315 citation statements)

References 331 publications

Supporting

Mentioning

296

Contrasting

Order By: Relevance

“…The ionization rates inferred from interstellar chemistry in molecular clouds also seem to indicate that the solar system cosmic ray environment is quite representative of the local Galaxy, as does the diffuse gamma-ray emission of the Galaxy (although at higher energies), see e.g. Grenier et al (2015).…”

Section: Numerical Estimates Using Voyager Datamentioning

confidence: 85%

Power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence

Drury

Strong

2017

A&A

Self Cite

View full text Add to dashboard Cite

We make quantitative estimates of the power supplied to the Galactic cosmic ray population by second-order Fermi acceleration in the interstellar medium, or as it is usually termed in cosmic ray propagation studies, diffusive reacceleration. Using recent results on the local interstellar spectrum from the Voyager missions we show that for parameter values, in particular the Alfvén speed, typically used in propagation codes such as Galprop to fit the B/C ratio, the power contributed by diffusive reacceleration is significant and can be of order 50% of the total Galactic cosmic ray power. The implications for the damping of interstellar turbulence are briefly considered.

show abstract

Section: Numerical Estimates Using Voyager Datamentioning

confidence: 85%

Power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence

Drury

Strong

2017

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The gamma-rays produced by CR nuclei along their interstellar journey can remotely probe the CR flux and spectrum across Galactic spiral arms, inside young stellar clusters and superbubbles, in the central molecular zone, and down to parsec scales inside nearby clouds. The current picture provided by the Fermi -LAT analyses does not provide sufficient resolution to probe theoretical expectations based on spiral distributions of CR sources and environmental changes in CR transport due to their streaming in the varying Galactic magnetic field [114] or to different levels of interstellar MHD turbulence powered by massive stars and supernovae [71,84]. With their much improved angular resolution and lower energy band, e-ASTROGAM observations can complement the Fermi -LAT archival data to probe the heterogeneity of the CR population in a variety of Galactic environments, across four decades in momentum around the maximum energy density.…”

Section: What Are the Cr Energy Distributions Produced Insidementioning

confidence: 89%

“…Yet, our knowledge of the production pathways and transport properties of LECRs is very rudimentary in our Galaxy, and even more so in the conditions of merger/starburst galaxies. In the Local Bubble, the pronounced break in CR momentum implied near one GeV by the Voyager and Fermi LAT data suggests that LECRs are advected off the plane by a local Galactic wind [71,122]. Beyond Voyager, indirect measures of the LECR flux at the low, ionizing, energies are uncertain by several orders of magnitude, even in the local ISM.…”

Section: What Are the Cr Energy Distributions Produced Insidementioning

confidence: 99%

The e-ASTROGAM mission

et al. 2017

View full text Add to dashboard Cite

e-ASTROGAM ('enhanced ASTROGAM') is a breakthrough Observatory space mission, with a detector composed by a Silicon tracker, a calorimeter, and an anticoincidence system, dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV -the lower energy limit can be pushed to energies as low as 150 keV, albeit with rapidly degrading angular resolution, for the tracker, and to 30 keV for calorimetric detection. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy. The mission will provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LIGO-Virgo-GEO600-KAGRA, SKA, ALMA, E-ELT, TMT, LSST, JWST, Athena, CTA, IceCube, KM3NeT, and the promise of eLISA.

show abstract

“…Thus observations and modelling of external galaxies will be a useful adjunct to studies of CRE propagation in the Milky Way, such as those using the GALPROP code (see discussion in e.g. Strong et al 2007;Grenier et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Modelling the cosmic ray electron propagation in M 51

Mulcahy

Fletcher

Beck

et al. 2016

A&A

View full text Add to dashboard Cite

Context. Cosmic ray electrons (CREs) are a crucial part of the interstellar medium and are observed via synchrotron emission. While much modelling has been carried out on the CRE distribution and propagation of the Milky Way, little has been done on normal external star-forming galaxies. Recent spectral data from a new generation of radio telescopes enable us to find more robust estimations of the CRE propagation. Aims. To model the synchrotron spectral index of M 51 using the diffusion energy-loss equation and to compare the model results with the observed spectral index determined from recent low-frequency observations with LOFAR. Methods. We solve the time-dependent diffusion energy-loss equation for CREs in M 51. This is the first time that this model for CRE propagation has been solved for a realistic distribution of CRE sources, which we derive from the observed star formation rate, in an external galaxy. The radial variation of the synchrotron spectral index and scale-length produced by the model are compared to recent LOFAR and older VLA observational data and also to new observations of M 51 at 325 MHz obtained with the GMRT. Results. We find that propagation of CREs by diffusion alone is sufficient to reproduce the observed spectral index distribution in M 51. An isotropic diffusion coefficient with a value of 6.6 ± 0.2 × 10 28 cm 2 s −1 is found to fit best and is similar to what is seen in the Milky Way. We estimate an escape time of 11 Myr from the central galaxy to 88 Myr in the extended disk. It is found that an energy dependence of the diffusion coefficient is not important for CRE energies in the range 0.01 GeV-3 GeV. We are able to reproduce the dependence of the observed synchrotron scale-lengths on frequency, with l ∝ ν −1/4 in the outer disk and l ∝ ν −1/8 in the inner disk.

show abstract

The Nine Lives of Cosmic Rays in Galaxies

Cited by 314 publications

References 331 publications

Power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence

Power requirements for cosmic ray propagation models involving diffusive reacceleration; estimates and implications for the damping of interstellar turbulence

The e-ASTROGAM mission

Modelling the cosmic ray electron propagation in M 51

Contact Info

Product

Resources

About