And then there was light: what determines the “active” zones of jets?

September 12, 2019
Phillips Auditorium

The energy release from black holes is a well-known problem of keen interest to many astrophysics sub-fields, from high-energy astroparticle physics to cosmology and galaxy evolution. For instance we know from the mismatch between ‘gastrophysics-free’ cosmological simulations and observations of the largest scales of structure, that black holes manage to communicate with regions well beyond their gravitational sphere of influence, and that outflows (particularly jets for the largest scales) must be the mechanism. We also know that black holes of all scales experience cycles of activity where the dominant form of energy output changes, and that jet-dominated phases are associated with the highest energy particle acceleration. The problem currently lies in tying all these phenomena together and being able to uniquely predict outflow properties as a function of accretion and environmental properties. In this talk I will discuss a problem I have been puzzling over for some time, which is the link between event-horizon scales and the particle acceleration that “lights up” the jets we observe, which relates to our ability to connect recent Event Horizon Telescope images to observations at other wavebands. In particular I will focus on some recent studies about an older problem well-known in ‘AGN circles’, but that is now being explored in real-time using transient jets from black hole X-ray binaries (BHXBs): what sets the so-called “dissipation zone” where the inner jets start to radiate? I will then discuss how these results can be used to inform our models of both EHT images, and help connect them to the multi-wavelength observations we perform each campaign, as well as increase our understanding of the source of ultra-high energy cosmic rays, TeV gamma-rays and neutrinos.

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