The interstellar cosmic-ray electron spectrum from synchrotron radiation and direct measurements.

By A. Strong, E. Orlando, T. Jaffe. 2011

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Aims. We exploit synchrotron radiation to constrain the low-energy interstellar electron spectrum, using various radio surveys and connecting with electron data from Fermi-LAT and other experiments. Methods. The GALPROP programme for cosmic-ray propagation, gamma-ray and synchrotron radiation is used. Secondary electrons and positrons are included. Propagation models based on cosmic-ray and gamma-ray data are tested against synchrotron data from 22 MHz to 94 GHz. Results. The synchrotron data confirm the need for a low-energy break in the cosmic-ray electron injection spectrum. The interstellar spectrum below a few GeV has to be lower than standard models predict, and this suggests less solar modulation than usually assumed. Reacceleration models are more difficult to reconcile with the synchrotron constraints. We show that secondary leptons are important for the interpretation of synchrotron emission. We also consider a cosmic-ray propagation origin for the low-energy break. Conclusions. Exploiting the complementary information on cosmic rays and synchrotron gives unique and essential constraints on electrons, and has implications for gamma rays. This connection is especially relevant now in view of the ongoing Planck and Fermi missions.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/4fbef0bb39563270838c143779c7a6841c23b2d0

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Citations in the corpus

Interpretation of AMS-02 electrons and positrons data (2014, background): “[180] and [181] as the result of an analysis based on synchrotron observations, thus completely independent from any detail concerning solar modulation.”
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV (2014, methodology): “The Galactic magnetic field is modeled according to Strong et al. (2011) using a local random field strength of 7.5 µG.”
DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA (2016, background): “Reasonable agreement has been obtained between propagation code predictions and observations at various wavelengths (Strong et al. 2007, 2011; Bouchet et al. 2011; Gaggero et al. 2013; Orlando & Strong 2013), but our knowledge of the distribution of CR sources, of injection spectra, of CR diffusion…”
An improved source-subtracted and destriped 408 MHz all-sky map (2014, background): “E-mail:mathieu.remazeilles@manchester.ac.uk † E-mail:clive.dickinson@manchester.ac.uk 2003a; Finkbeiner 2004; Jaffe et al. 2011; Strong et al. 2011; Orlando & Strong 2013; Mertsch & Sarkar 2013), as well as Galactic sources such as supernova remnants (Sushch & Hnatyk 2014; Xiao & Zhu 2014) and HII…”
Galactic synchrotron emission with cosmic ray propagation models (2013, background): “In our previous paper (Strong et al. 2011), hereafter SOJ2011, we focussed on the total synchrotron spectrum only at high Galactic latitudes, from which we derived information on the electron spectrum and the total B-field.”
NINE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: FINAL MAPS AND RESULTS (2012, methodology): “Strong et al. (2011) have compared mid-latitude synchrotron measurements and estimates from 22 MHz to 94 GHz with predictions of cosmic ray propagation models based on cosmic ray and gamma ray data.”
THE GALACTIC MAGNETIC FIELD (2012, background): “…and rescaling the GALPROP ncre, as could arise if anisotropic diffusion due to the out-of-plane field were incorporated in GALPROP, further improves the fit; Strong et al. (2011) and Jaffe et al. (2011) have also shown evidence of a need for a modification in the intersteller electron spectrum.”