Skip to Main Content

New article in Nat Commun by grad student Adam Leah Harvey

October 29, 2020 8:49 AM
“Powerful extragalactic jets dissipate their kinetic energy far from the central black hole”

Harvey, A.L.W., Georganopoulos, M. & Meyer, E.T.

Adam Leah W. Harvey, Markos Georganopoulos, and Eileen T. Meyer have placed substantial constraints on the dominant location of kinetic energy dissipation in powerful extragalactic jets. Constraining the dominant site of energy dissipation has been an open problem for decades. The authors used empirical fitting of jet spectral energy distributions, and a diagnostic developed by Dr. Georganopoulos to place statistical constraints on this location, finding that the dominant site of energy dissipation is strongly preferred to be located far from the supermassive black holes powering these jets.

Nature Communications volume 11, Article number: 5475 (2020).

URL: https://www.nature.com/articles/s41467-020-19296-6

Abstract: Accretion onto the supermassive black hole in some active galactic nuclei (AGN) drives relativistic jets of plasma, which dissipate a significant fraction of their kinetic energy into gamma-ray radiation. The location of energy dissipation in powerful extragalactic jets is currently unknown, with implications for particle acceleration, jet formation, jet collimation, and energy dissipation. Previous studies have been unable to constrain the location between possibilities ranging from the sub-parsec-scale broad-line region to the parsec-scale molecular torus, and beyond. Here we show using a simple diagnostic that the more distant molecular torus is the dominant location for powerful jets. This diagnostic, called the seed factor, is dependent only on observable quantities, and is unique to the seed photon population at the location of gamma-ray emission. Using 62 multiwavelength, quasi-simultaneous spectral energy distributions of gamma-ray quasars, we find a seed factor distribution which peaks at a value corresponding to the molecular torus, demonstrating that energy dissipation occurs ~1 parsec from the black hole (or ~1e4 Schwarzchild radii for a 1e9 solar mass black hole).