Owen, ER;
Jacobsen, IB;
Wu, K;
Surajbali, P;
(2018)
Interactions between ultra-high-energy particles and protogalactic environments.
Monthly Notices of the Royal Astronomical Society
, 481
(1)
pp. 666-687.
10.1093/mnras/sty2279.
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Abstract
We investigate the interactions of energetic hadronic particles (cosmic ray protons) with photons and baryons in protogalactic environments, where the target photons are supplied by the first generations of stars to form in the galaxy and the cosmological microwave background, while the target baryons are the interstellar and circumgalactic medium. We show that pair-production and photo-pion processes are the dominant interactions at particle energies above 1019 eV, while proton-proton (pp) interaction pion-production dominates at the lower energies in line with expectations from, for example γ-ray observations of star-forming galaxies and dense regions of our own galaxy’s interstellar medium. We calculate the path lengths for the interaction channels and determine the corresponding rates of energy deposition. We have found that protogalactic magnetic fields and their evolution can significantly affect the energy transport and energy deposition processes of cosmic rays. Within a Myr after the onset of star-formation the magnetic field in a protogalaxy could attain a strength sufficient to confine all but the highest energy particles within the galaxy. This enhances the cosmic ray-driven self-heating of the protogalaxy to a rate of around 10−24 erg cm−3 s−1 for a galaxy with strong star-forming activity that yields one core collapse supernova event per year. This heating power exceeds even that due to radiative emission from the protogalaxy’s stellar populations. However, in a short window before the protogalaxy is fully magnetized, energetic particles could stream across the galaxy freely, delivering energy into the circumgalactic and intergalactic medium.
| Type: | Article |
|---|---|
| Title: | Interactions between ultra-high-energy particles and protogalactic environments |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/sty2279 |
| Publisher version: | https://doi.org/10.1093/mnras/sty2279 |
| Language: | English |
| Additional information: | This version is the version of the record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | cosmic rays, ISM: evolution, ISM: magnetic fields, galaxies: clusters: general, galaxies: high-redshift |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10056494 |
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