Nature’s Death Stars: A Discussion of Supermassive Black Holes, Relativistic Jets, and The Event Horizon Telescope.

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Speaker :  
Dr. Nicholas Roy MacDonald (Max Planck Institute for Radio Astronomy, Germany)
Location :  
Online seminar
Date :  

Time : 

Abstract :

What are relativistic jets made of? The answer is central to our understanding of how supermassive black holes influence their surrounding galactic environments. In this talk I will present my research on the composition of relativistic jets (and in particular blazars) within the context of the Event Horizon Telescope (EHT) collaboration.

Blazars represent an extreme subclass of active galactic nuclei (AGN), in which an accreting supermassive black hole launches and powers a relativistic jet of magnetized plasma that is closely aligned to our line-of-sight. Blazar jets: (i) shine across the entire electromagnetic spectrum (from low-frequency radio waves to high-energy gamma-rays), (ii) exhibit dramatic flares, and (iii) dominate the high-energy extragalactic sky. Very long baseline interferometric (VLBI) arrays (such as phased ALMA & The Event Horizon Telescope) are capable of imaging the polarized synchrotron emission emanating from the innermost regions of relativistic blazar jets with unprecedented angular resolution and sensitivity. In particular, the linearly and circularly polarized synchrotron emission from blazars carry imprints of both the strength and orientation of the collimating magnetic fields as well as the plasma content of each jet. In parallel to these advances in VLBI imaging, modern computational resources now support the production and execution of increasingly sophisticated 3D numerical jet simulations, from semi-analytic shock-in-jet and turbulence models, to relativistic magneto-hydrodynamic (RMHD) and particle-in-cell (PIC) jet plasma simulations.

My research focuses on bridging the gap between these 3D relativistic jet simulations and mm-wave global VLBI observations of blazar jets through the application of ray-tracing and polarized radiative transfer. In this talk, I will present a suite of relativistic jet simulations that attempt to place firmer constraints on the as yet unknown plasma content of black hole jets.