Owen, Ellis Richard;
(2019)
Hadronic Processes of Energetic Particles in Star-Forming Galaxies and High-Redshift Protogalactic Environments.
Doctoral thesis (Ph.D), UCL (University College London).
Preview |
Text
thesis_FINAL.pdf Download (2MB) | Preview |
Abstract
In this thesis, the heating and feedback effect of energetic cosmic rays (CRs) in star-forming galaxies and protogalaxies is investigated. Galaxies undergoing violent starburst episodes are expected to be rich in CRs. This is due to an abundance of stellar end-products (which are able to accelerate CRs up to PeV energies), coupled with the rapid development of a µG interstellar magnetic field soon after the onset of star-formation, which is able to contain CRs inside the host galaxy. Hadronic CR particles can undergo interactions with photons and baryons. In star-forming galaxies, target photons are supplied by stellar radiation and the cosmological microwave background, while target baryons comprise the interstellar and circumgalactic medium. CR interactions enable their deposition of energy, causing the surrounding medium to be heated. This occurs either by the Coulomb thermalisation, or by the inverse Compton X-ray emission, of CR secondary particles (which are injected by the hadronic CR interactions). CR heating processes are found to attain a power of 10−25 erg cm−3s−1 in an idealised galaxy with 1 core collapse SN event per decade. This falls to 10−28 erg cm−3s−1 if concentrated starburst activity in the system leads to the development of a galactic-scale outflow. It is argued that CR-driven heating processes can lead to quenching and/or stunning of subsequent star-formation activity in the host. The level of CR feedback in 16 observed starburst/post-starburst high-redshift galaxies is estimated, based on the star-formation rates they could have sustained during their starburst episodes. It is found that CR feedback cannot be neglected in these systems: it has the strength to suppress star-formation, and can even maintain a post-starburst period of quiescence which is consistent with their inferred star-formation histories.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Hadronic Processes of Energetic Particles in Star-Forming Galaxies and High-Redshift Protogalactic Environments |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10080904 |
Archive Staff Only
 |
View Item |
