Clausen-Brown, Eric

AGN jet physics and observed apparent opening angles.

Author list: Eric Clausen-Brown, Tuomas Savolainen, Alexander B. Pushkarev, Yuri Y. Kovalev, Matthew L. Lister

I will present a new method to measure the product of jet Lorentz factor and intrinsic opening angle in flux-limited samples of active galactic nuclei (AGN) jets. This parameter is physically important for jet launching and jet dynamics since it is related to jet sidewise expansion velocity and causality. The measurement is carried out by analyzing the observed distribution of apparent opening angles in very long baseline interferometry (VLBI) flux-limited samples of jets, given some prior knowledge of the AGN radio luminosity function. When applied to the MOJAVE flux-limited sample of radio loud objects, I find the product of jet half-opening angle and Lorentz factor to be 0.1 ± 0.03, which implies that AGN jets are causally connected. In contrast, this parameter is typically two orders of magnitude higher in gamma-ray burst jets, suggesting significant physical differences between AGN jets and GRB jets. I also find evidence that AGN jets viewed very close to the line of sight effectively have smaller intrinsic opening angles than jets viewed more off-axis, which is consistent with Doppler beaming and a velocity field consisting of a fast inner spine and slow outer sheath.