Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies
The origin of ultra-high energy cosmic rays (UHECRs) has been an open question for decades. Here, we use a combination of hydrodynamic simulations and general physical arguments to demonstrate that UHECRs can in principle be produced by diffusive shock acceleration (DSA) in shocks in the backflowing...
| Váldodahkkit: | , , , |
|---|---|
| Materiálatiipa: | Journal article |
| Almmustuhtton: |
Oxford University Press
2018
|
| _version_ | 1826274725760860160 |
|---|---|
| author | Matthews, J Bell, B Blundell, K Araudo, A |
| author_facet | Matthews, J Bell, B Blundell, K Araudo, A |
| author_sort | Matthews, J |
| collection | OXFORD |
| description | The origin of ultra-high energy cosmic rays (UHECRs) has been an open question for decades. Here, we use a combination of hydrodynamic simulations and general physical arguments to demonstrate that UHECRs can in principle be produced by diffusive shock acceleration (DSA) in shocks in the backflowing material of radio galaxy lobes. These shocks occur after the jet material has passed through the relativistic termination shock. Recently, several authors have demonstrated that highly relativistic shocks are not effective in accelerating UHECRs. The shocks in our proposed model have a range of non-relativistic or mildly relativistic shock velocities more conducive to UHECR acceleration, with shock sizes in the range 1 − 10 kpc. Approximately 10% of the jet’s energy flux is focused through a shock in the backflow of M > 3. Although the shock velocities can be low enough that acceleration to high energy via DSA is still efficient, they are also high enough for the Hillas energy to approach 1019−20 eV, particularly for heavier CR composition and in cases where fluid elements pass through multiple shocks. We discuss some of the more general considerations for acceleration of particles to ultra-high energy with reference to giant-lobed radio galaxies such as Centaurus A and Fornax A, a class of sources which may be responsible for the observed anisotropies from UHECR observatories. |
| first_indexed | 2024-03-06T22:47:50Z |
| format | Journal article |
| id | oxford-uuid:5dcaf9e9-1212-4258-9765-7a0438bdaf1f |
| institution | University of Oxford |
| last_indexed | 2024-03-06T22:47:50Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:5dcaf9e9-1212-4258-9765-7a0438bdaf1f2022-03-26T17:36:32ZUltra-high energy cosmic rays from shocks in the lobes of powerful radio galaxiesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:5dcaf9e9-1212-4258-9765-7a0438bdaf1fSymplectic Elements at OxfordOxford University Press2018Matthews, JBell, BBlundell, KAraudo, AThe origin of ultra-high energy cosmic rays (UHECRs) has been an open question for decades. Here, we use a combination of hydrodynamic simulations and general physical arguments to demonstrate that UHECRs can in principle be produced by diffusive shock acceleration (DSA) in shocks in the backflowing material of radio galaxy lobes. These shocks occur after the jet material has passed through the relativistic termination shock. Recently, several authors have demonstrated that highly relativistic shocks are not effective in accelerating UHECRs. The shocks in our proposed model have a range of non-relativistic or mildly relativistic shock velocities more conducive to UHECR acceleration, with shock sizes in the range 1 − 10 kpc. Approximately 10% of the jet’s energy flux is focused through a shock in the backflow of M > 3. Although the shock velocities can be low enough that acceleration to high energy via DSA is still efficient, they are also high enough for the Hillas energy to approach 1019−20 eV, particularly for heavier CR composition and in cases where fluid elements pass through multiple shocks. We discuss some of the more general considerations for acceleration of particles to ultra-high energy with reference to giant-lobed radio galaxies such as Centaurus A and Fornax A, a class of sources which may be responsible for the observed anisotropies from UHECR observatories. |
| spellingShingle | Matthews, J Bell, B Blundell, K Araudo, A Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title | Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title_full | Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title_fullStr | Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title_full_unstemmed | Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title_short | Ultra-high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| title_sort | ultra high energy cosmic rays from shocks in the lobes of powerful radio galaxies |
| work_keys_str_mv | AT matthewsj ultrahighenergycosmicraysfromshocksinthelobesofpowerfulradiogalaxies AT bellb ultrahighenergycosmicraysfromshocksinthelobesofpowerfulradiogalaxies AT blundellk ultrahighenergycosmicraysfromshocksinthelobesofpowerfulradiogalaxies AT araudoa ultrahighenergycosmicraysfromshocksinthelobesofpowerfulradiogalaxies |