E4: From MeV to TeV. Extracting the spectrum of cosmic rays at their sources over 6 orders of magnitude in energy

  • The goal of this research project is to extract from currently available data the spectrum of cosmic rays at their acceleration sites over more than six orders of magnitude in energy: from the ~MeV to the multi-TeV domain. This task, impracticable until very recently, is now possible due to unprecedented observations of supernova remnants in both the millimetre and gamma-ray domains of the electromagnetic spectrum, and will constitute a crucial step towards the solution of the problem of the origin of Galactic cosmic rays.
    Very recent observations in the near infrared and millimetre domain made possible to measure the Cosmic Ray (CR) ionisation rate in a handful of Molecular Clouds (MC) located next to SuperNova Remnants (SNR). In all these cases the SNR shock is interacting with the MC. The ionization rates found in this way are significantly enhanced (up to a factor of 100!) with respect to the average value found in isolated MCs (Ceccarelli et al. 2011; Vaupre et al. 2014). This striking difference is interpreted as an evidence for a strongly enhanced intensity of ~MeV CRs in those MCs which are interacting with SNRs. Moreover, the same clouds from which enhanced ionization rates have been inferred have been also detected in gamma rays (see e.g. Rieger et al. 2013). That also requires an enhancement in the CR intensity, though in this case particles with much larger energies, up to ~10-100 TeV, have to be invoked. Both these facts provide a strong support to the popular (but not conclusively proven yet) conjecture that SNRs are the sources of CRs. The goal of the proposed research is to combine these two observables and, after complementing them with thorough and original theoretical investigations, obtain information on the spectrum of CRs at their (presumed) sources within a huge interval spanning more than six orders of magnitude in particle energy. This unprecedented constraints will shed light on the way in which CRs are injected, accelerated, and finally escape SNRs, thus providing a novel and powerful approach to confront, and possibly solve, the long-standing issue of the origin of CRs.
    Remarkably, the impact of the research proposed here goes far beyond the field of CR physics. This is because the ionization level in MCs, set mainly by CRs, regulates the coupling between magnetic field and gas. Such coupling in turn determines the level of magnetic support against the cloud’s gravitational collapse. Thus, results from this project will play a pivotal role in studies of star and planet formation.

  • From APC laboratory:

    Stefano Gabici (PI) – stefano.gabici@apc.univ-paris7.fr
    Arache Djannati-Atai – djannati@in2p3.fr
    Etienne Parizot – parizot@apc.univ-paris7.fr
    Regis Terrier – terrier@apc.univ-paris7.fr

    From AIM laboratory:

    Patrick Hennebelle (PI) – Patrick.HENNEBELLE@cea.fr
    Jean Ballet – jean.ballet@cea.fr
    Karl Kosack – karl.kosack@cea.fr
    Isabelle Grenier – isabelle.grenier@cea.fr

  • Simulations and theoretical computations on the propagation of cosmic rays into molecular clouds are in progress. Results will be announced on this page soon.

  • – Vaupre, S., Hily-Blant, P., Ceccarelli, C., Dubus, G., Gabici, S., Montmerle, T., 2014, A&A, 568, A50
    – Dumas, G., Vaupre, S., Ceccarelli, C., Hily-Blant, P., Dubus, G., Montmerle, T., Gabici, S., 2014, ApJ Lett., 786, L24