标题：Radio-loud Active Galactic Nucleus Variability from Three-dimensional Propagating Relativistic Jets
作者：Li, Yutong; Wiita, Paul J.; Schuh, Terance; Elghossain, Geena; Hu, Shaoming
作者机构：[Li, Yutong; Hu, Shaoming] Shandong Univ, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Inst Space Sci, Weihai 264209, Peoples R China.; [Li, Y 更多
通讯作者：Li, YT;Li, YT
通讯作者地址：[Li, YT]Shandong Univ, Shandong Prov Key Lab Opt Astron & Solar Terr Env, Inst Space Sci, Weihai 264209, Peoples R China;[Li, YT]Coll New Jersey, Dept 更多
关键词：BL Lacertae objects: general; galaxies: active; galaxies: jets;; hydrodynamics; quasars: general
摘要：The enormous sizes and variability of emission of radio-loud active galactic nuclei arise from the relativistic flows of plasma along two oppositely directed jets. We use the Athena hydrodynamics code to simulate an extensive suite of 54 propagating three-dimensional relativistic jets with wide ranges of input jet velocities and jet-to-ambient matter density ratios. We determine which parameter sets yield unstable jets that produce jet-dominated Fanaroff-Riley I (FR I) radio galaxy morphologies and which tend to produce stable jets with hot spots and FR II morphologies. Nearly all our simulations involve jets with internal pressures matched to those of the ambient medium but we also consider over-pressured jets and discuss differences from the standard ones. We also show that the results are not strongly dependent on the adiabatic index of the fluid. We focus on simulations that remain stable for extended distances (60-240 times the initial jet radius). Scaled to the much smaller sizes probed by very long baseline interferometry observations, the fluctuations in such simulated flows yield variability in the observed emissivity on timescales from months. Adopting results for the densities, pressures, and velocities from these simulations, we estimate normalized rest frame synchrotron emissivities from individual cells in the jets. The observed emission from each cell is strongly dependent upon its variable Doppler boosting factor. We sum the fluxes from thousands of zones around the primary reconfinement shock. The light curves and power spectra, with red-noise slopes between -2.1 and -2.5, so produced are similar to those observed from blazars.