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Astrophysical Messengers

Modelling and analysis of energetic astrophysical particles

The Universe has long been studied using optical light. More recently, this view has been expanded to include the complete electromagnetic spectrum, from radio to gamma-rays, unveiling a Universe of energetic and diverse sources that can be analyzed from vast distances and early epochs. Astrophysical particles — cosmic rays and neutrinos — have also been added to the messengers that can be used to investigate the cosmos.

Our research concerns the most energetic astrophysical particles. In order to detect these rare messengers, researchers use detectors monitoring the Earth’s atmosphere, ice sheets, and oceans. Cosmic rays are charged particles, i. e. protons and the nuclei of heavier elements, that have been accelerated to high energies. While we can detect cosmic rays up to ultra-high energies, their origins are unclear. Charged particles interact with their environment as they travel toward the Earth, leading to energy losses and deflections in magnetic fields, which make it challenging to localize their origins. Possible sources capable of accelerating particles to extreme energies include gamma-ray bursts, active galactic nuclei, blazars, and galaxy clusters.

Messengers from space: Cosmic objects emit neutrinos (violet), gamma rays (orange) and protons (green). (Picture: superbossa.com/MPP)
Messengers from space: Cosmic objects emit neutrinos (violet), gamma rays (orange) and protons (green). (Picture: superbossa.com/MPP)

The interactions of cosmic rays with matter and radiation fields along their path lead to the production of gamma rays and neutrinos. These electrically neutral messengers can travel undeflected to Earth and provide complementary information. However, the interpretation of these observations presents further challenges. Gamma rays can also be produced by non-hadronic processes that must be disentangled from signatures of particle acceleration. Neutrinos are a direct sign of hadronic processes but are weakly interacting and not easily detected. Combining the observations of these messengers will provide a detailed new view of energetic astrophysical objects and a laboratory for studying particle physics at extreme energies.

Today, there are large-scale experimental efforts in place, meaning that there are many relevant data sets available. For example, the Pierre Auger and Telescope Array ultra-high-energy cosmic ray experiments and the IceCube neutrino observatory have collected rich data sets over 10 to 20 years of operation. In the field of gamma-ray astronomy, the astrophysical messenger group will co-operate with the MAGIC and CTA groups at the MPP. Our goal is to develop advanced statistical analysis methods to exploit the available data to its full potential and gain a deeper understanding of the possible sources of these energetic particles. These new approaches focus on complementing existing efforts by enabling a closer connection between theory and data and effectively combining information from different observations.

Group "Astrophysical Messengers"

E-mail address: e-mail@mpp.mpg.de
Phone number: +49 89 32354-extension
name function e-mail extension office
Bourriche, Nadine PhD Student nadineb 561 A.2.07
Capel, Francesca, Dr. Senior Scientist capel 417 A.2.09
Kuhlmann, Julian PhD Student kuhlmann 561 A.2.07
Rego, Avalon Student rego 417 A.2.07
Saurenhaus, Lena PhD Student lsaurenh 561 A.2.07

Francesca Capel (Photo: Axel Griesch/MPP)

Francesca Capel (Photo: Axel Griesch/MPP)

Francesca Capel heads new research group at MPP

The Max Planck Institute for Physics (MPP) welcomes Francesca Capel. Starting May 1, 2022, the postdoctoral researcher will head a working group for the closer study of astrophysical particles - cosmic rays and neutrinos. These high-energy particles are accelerated by powerful and distant sources, but their exact origin remains unclear to this day. The astrophysicist will receive a three-year grant through the Minerva Fast Track Program for outstanding young female scientists.

Where do the highest-energy particles in the universe come from? This is the question Francesca Capel will focus on at the MPP over the next three years. According to current understanding, cosmic rays consist of protons, i. e. hydrogen nuclei, as well as the nuclei of heavier elements, which could be accelerated to extreme energies in extragalactic sources.  

Their path through the universe is not straight: The positively charged particles interact with matter and are deflected by magnetic fields. However, they leave behind them a trail of photons (particles of light) and neutrinos that can reach Earth without detours.  

Together with her research group, Capel will study these different signals: cosmic rays, neutrinos and photons. “These signals can be thought of as messengers, carrying different information about their place of origin and the environments through which they have travelled. By studying them together, we can deepen our understanding of their astrophysical sources", says Francesca Capel.

Large-scale experimental collaborations, including the MAGIC/CTA gamma-ray telescopes (active at the MPP) and the IceCube neutrino observatory, have gathered large amounts of relevant data. “These data sets are very complex, and bringing the information together effectively requires advanced data analysis tools,” says Capel. The development of statistical methods will be a vital part of this research at the intersection of experiment and theory.  

Prior to taking her new position at MPP, Capel was a postdoctoral researcher at the Data Science Lab of the ORIGINS Cluster of Excellence. She earned her doctorate in astroparticle physics at KTH Royal Institute of Technology in Stockholm. Her master’s degree in physics was completed at Imperial College in London, including a one-year thesis project at the École Polytéchnique Fédérale de Lausanne through the Erasmus program. Her group will also be supported by the Cluster of Excellence ORIGINS and the SFB-1258, in both of which the MPP is a partner institution.  

About the Minerva Program  

The program is aimed at PhDs in chemistry, physics and engineering, or in the humanities and social sciences. It provides outstanding female scientists with an early, forward-looking career option following their doctorate. Minerva Fast Track Fellowships are awarded once a year following a nomination process and subsequent evaluation. The funded female researchers receive extra funding for up to three years (material and personnel resources). After that, they have the opportunity to apply for a Max Planck Research Group.  

Bayesian constraints on the astrophysical neutrino source population from IceCube data
Capel, F., Mortlock D. J. & Finley, C.
2020, Physical Review D, 101, 123017
DOI: 10.1103/PhysRevD.101.123017

 

Impact of using the ultra-high-energy cosmic ray arrival energies to constrain source associations
Capel, F. & Mortlock, D. J.
2019, Monthly Notices of the Royal Astronomical Society, 484, 2324.
DOI: 10.1093/mnras/stz081

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