Identification of cosmic ray sources amongst jetted active galaxies

Welcome to the webpage of the joint FWF-ARRS project

Cosmic Rays (CRs) are energetic, mostly charged particles of cosmic origin. A dedicated method is developed in this project with the goal to determine to which extent ultra-high energy (UHE, ≥ 10 EeV) CRs originate from jetted active galactic nuclei.

Recent measurement results favor conventional scenarios of the UHECR production at astrophysical sites. Prominent jet outflows in powerful active galactic nuclei (AGN) provide suitable conditions for charged particle acceleration up to UHEs, and are thus considered prime contributors to the observed UHECR flux. During CR acceleration, hadronic interactions occur where photons and neutrinos are produced. As neutral messengers, they provide information about the CR source location in the sky, and the physical conditions at the CR production site, while the charged CRs suffer from loss of directional information by deflections in cosmic magnetic fields. To reach the project goal, we employ a multi-messenger, multi-wavelength (MWL) approach including measurements of 1) UHECRs by the Pierre Auger Observatory, 2) gamma-rays of high- (HE, ≥ 100 MeV), by the Fermi-LAT detector, and very-high energy (VHE, ≥ 30 GeV), by ground-based Cherenkov telescopes, and 3) VHE neutrinos by the IceCube experiment.

In the proposed multistep procedure, all nearby AGN are first classified according to their capability to accelerate particles to UHEs. For this purpose, we use MWL measurements of the AGN electromagnetic spectra, complemented with AGN emission models to build a list of suitable AGN candidates for UHECR acceleration. Auger data indicate that the CR flux composition at extreme energies trends from light towards intermediate mass nuclei. Therefore current state-of-the-art AGN emission models will be extended (by the Austrian project team under the lead of Dr. A. Reimer) to include injection, transport and radiative losses of particle distributions of heavy nuclei composition. The Slovenian project team (led by Dr. S. Vorobiov) will develop and perform subsequent simulations of possible UHECR arrival directions for various cosmic magnetic field configurations, based on the AGN candidate list. The resulting UHECR patterns expected at Earth will be cross-correlated with Auger data. The signatures of the produced photon and neutrino emission will be analyzed and their relation to Fermi-LAT and IceCube data investigated as well. Finally, characteristic UHECR features stemming from AGN jets, and verifiable by the near-future Cherenkov Telescope Array (CTA), will be predicted.

This project benefits from the participation of numerous world leading scientists from Italy and Poland. It is expected to lead to valuable results towards identifying the sources of the UHECRs and optimizing the CTA observation strategies for this science case.


September 1, 2021
During this week the joint meeting of the Austrian and Swiss physical societies (ÖPG and SPS) is taking place in Innsbruck. The project team used the opportunity to present our research to a broad (non-astroparticle) community with a talk (see our publications).

July 30, 2021
The latest results from our project have been presented in various forms at the 37th International Cosmic Ray Conference (ICRC) during the last two weeks, where we received valuable feedback by colleagues from all around the world. Our findings have also been published in Proceedings of Science (see our publications). Here, the project team presented an early study on the propagation of UHECR from FR-0s to our Galaxy.

May 1, 2021
Paolo Da Vela is now engaging full time in the project team. With his expertise in high energy gamma ray physics he will help to model candidate source regions, e.g. FR 0 radio galaxies.

February 14, 2021
The first article of the project team was published and is freely avalaible. We could show that based on a hybrid acceleration scenario, combining Fermi I order and gradual shear acceleration, UHECRs can be accelerated in FR 0 jets and escape the prevailing photon target fields. This is a first step in examing the FR 0 contribution to the observed UHECR flux.

December 09, 2020
Today we presented our work on FR 0 radio galaxies as possible UHECR source candidates at the international YITP workshop "Connecting high-energy astroparticle physics for origins of cosmic rays and future perspectives” that was hosted as a hybrid event in Kyoto, JAP. The abstract and our slides will become available on the workshop homepage.

May 14, 2020
Yesterday the remote face-2-face meeting ended after two days full of inspiring discussions. The complete team virtually gathered for four sessions dedicated to the fields of the research project: multimessenger observation, a source catalogue, source physics, and multimessenger propagation. The full schedule can be found on the meeting page.
Although the meeting was a great success, still all participants are hoping to meet in person on the next possible occasion.

April 7, 2020
Today the project team has decided to postpone the face2face meeting in Nova Gorica due to the severe Covid-19 outbreak. Although the bi-yearly in-person meetings are an important factor for the success of the project, they are unfortunatly not possible under the given circumstances. The scheduled meeting will now be transformed to a virtual meeting to allow for the essential exchange of ideas. It is planned to make up for the F2F-meeting in Nova Gorica at a later point in time.

March 3, 2020
We are happy to announce that two new members joined our research team in February. Margot Boughelilba, a PhD student in Innsbruck, will work on a numerical simulation to describe cosmic ray physics inside the jets. The Slovenian team is strengthened by Jon Paul Lundquist, who is helping to improve the modelling of the cosmic ray transport from the sources to Earth.

November 11, 2019
The webpage was officially launched today. We will keep you updated on this existing project here on this page. Get to know the collaborators or learn about the resources that will become available for the scientific community during the project.

October 15, 2019
The kick-off meeting of the project is about to take place in Innsbruck very soon (October 28-30, 2019). At this first face-to-face appointment all members of the international team will get to know each other and start discussion on science of cosmic rays originating in active galaxies. More information on the meeting can be found at the collaboration meeting page.

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