There is a general consensus that every galaxy harbors a supermassive black hole (SMBH) at its nucleus. While we cannot easily study these exotic objects directly, we can investigate how they interact with their surroundings. When an SMBH accretes matter, it becomes active and starts radiating, primarily emitting thermal photons from the accretion disk that feeds it. These accreting SMBHs, known as Active Galactic Nuclei (AGNs), are among the brightest sources of photons in the Universe.

In a subset of AGNs, accretion is accompanied by the ejection of a highly relativistic, collimated plasma jet along the polar axis of the system. When this plasma jet is oriented close to the observer's line of sight, relativistic effects enhance the observed flux, making these objects exceptionally bright in the sky. AGNs with jets aligned in this way are referred to as blazars.

Blazars are the most common gamma-ray sources in the extragalactic sky, and there is evidence suggesting they are also neutrino emitters. Photons and neutrinos from blazars are produced in the jet, provided there is a population of high-energy hadrons (protons and nuclei). Such radiation models are referred to as hadronic models to emphasize the role of protons in the observed emissions. These high-energy protons, once they reach Earth, are identified as cosmic rays. Multi-messenger observations of photons and neutrinos from AGNs can therefore help constrain the role of these objects as natural accelerators of cosmic rays.

The goal of this internship is for the student to first learn the basics of AGN physics, blazars, and hadronic radiative models. The student will then have the opportunity to work with a proprietary hadronic code we have developed. Using this code, the student will analyze a source of interest, performing a multi-messenger fit to the data to constrain the properties of the jet's emitting region and the hadron distribution within it.