PhD Proposal: Rafael Diaz Brenes
Location
Physics : 401
Date & Time
April 22, 2025, 3:00 pm – 4:40 pm
Description
ADVISOR: Dr. Eileen Meyer
TITLE: High-energy Emission in Jets From parsec to Megaparsec Scales
ABSTRACT: Active galactic nuclei (AGN) with strong radio emission, also known as Radio-Loud AGN, are known to host high-energy relativistic jets that extend up to kiloparsec scales. When these jets happen to be aimed at or near the observer's line of sight, relativistic beaming effects (Doppler boosting) causes the apparent luminosity of the non-thermal jet radiation to be enhanced by several orders of magnitude. These relativistic jets emit radiation with a broad, multi-component spectrum, from radio up to gamma-rays and reaching multi-TeV photon energies. The emission mechanisms of the higher-energy (X-ray to gamma-ray) emission is still not fully understood in many cases. On kpc scales, far from the central engine, many jets are far more luminous in the X-rays than expected for a decelerated leptonic jet. It has been argued that this X-ray emission corresponds to synchrotron emission from a secondary population of relativistic electrons. In part I of my project, I will conduct a multi-wavelength study of X-ray jet sources with extensive gamma-ray observations from the VERITAS observatory, which operates at energies above 1 TeV. These very-high-energy (VHE) observations can finally confirm the synchrotron nature of the jet X-rays by detecting inverse-Compton (IC) scattering of the cosmic microwave background radiation (CMB) by the same electrons that produce the X-ray emission. In part II of my project, I will extend an existing numerical relativistic magneto-hydrodynamic (RMHD) jet simulation code with IC scattering and polarization tracing to improve our predictions for polarization degree and changes in relativistic jets under so-called hadronic models, which deposit relativistic (rather than 'cold' protons in the radiating plasma. This code will then allow us to test applicability of the different jet models to actual observations and to improve our understanding of how jets are structured, accelerate particles, and radiate on scales both near and far from the central black hole engine.
TITLE: High-energy Emission in Jets From parsec to Megaparsec Scales
ABSTRACT: Active galactic nuclei (AGN) with strong radio emission, also known as Radio-Loud AGN, are known to host high-energy relativistic jets that extend up to kiloparsec scales. When these jets happen to be aimed at or near the observer's line of sight, relativistic beaming effects (Doppler boosting) causes the apparent luminosity of the non-thermal jet radiation to be enhanced by several orders of magnitude. These relativistic jets emit radiation with a broad, multi-component spectrum, from radio up to gamma-rays and reaching multi-TeV photon energies. The emission mechanisms of the higher-energy (X-ray to gamma-ray) emission is still not fully understood in many cases. On kpc scales, far from the central engine, many jets are far more luminous in the X-rays than expected for a decelerated leptonic jet. It has been argued that this X-ray emission corresponds to synchrotron emission from a secondary population of relativistic electrons. In part I of my project, I will conduct a multi-wavelength study of X-ray jet sources with extensive gamma-ray observations from the VERITAS observatory, which operates at energies above 1 TeV. These very-high-energy (VHE) observations can finally confirm the synchrotron nature of the jet X-rays by detecting inverse-Compton (IC) scattering of the cosmic microwave background radiation (CMB) by the same electrons that produce the X-ray emission. In part II of my project, I will extend an existing numerical relativistic magneto-hydrodynamic (RMHD) jet simulation code with IC scattering and polarization tracing to improve our predictions for polarization degree and changes in relativistic jets under so-called hadronic models, which deposit relativistic (rather than 'cold' protons in the radiating plasma. This code will then allow us to test applicability of the different jet models to actual observations and to improve our understanding of how jets are structured, accelerate particles, and radiate on scales both near and far from the central black hole engine.
