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We present a 16-month sequence of monthly polarimetric 43 GHz VLBA images of the radio galaxy 3C 120. The images probe the inner regions of the radio jet of this relatively nearby superluminal radio galaxy at a linear resolution of 0.07 $h_{65}^{-1}$ pc ($H_o= 65 h_{65}$ km s$^{-1}$ Mpc$^{-1}$). We follow the motion of a number of features with apparent velocities between 4.01$pm$0.08 and $5.82pm 0.13 h_{65}^{-1} c$. A new superluminal knot, moving at $4.29pm 0.16 h_{65}^{-1} c$, is observed to be ejected from the core at a time coincident with the largest flare ever observed for this source at millimeter wavelengths. Changes in the position angle of this component, as well as a progressive rotation of its magnetic polarization vector, suggest the presence of a twisted (resembling a helix in projection) configuration of the underlying jet magnetic field and jet geometry. We identify several knots that appear in the wake of the new superluminal component, moving at proper motions $sim 4$ times slower than any of the other moving knots observed in 3C 120. These features have properties similar to those of the ``trailing shocks seen in relativistic, time-dependent, hydrodynamical and emission simulations of compact jets. Such trailing compressions are triggered by pinch-mode jet-body instabilities caused by the propagation of a strong perturbation, which we associate with the new strong superluminal component.
We aim to better understand the dynamics within relativistic magneto-hydrodynamical flows in the extreme environment and close vicinity of supermassive black holes. To do so, we analyze the peculiar radio galaxy 3C 111, for which long-term polarimetr
In this first of a series of papers describing polarimetric multifrequency Very Long Baseline Array (VLBA) monitoring of 3C 273 during a simultaneous campaign with the INTEGRAL gamma-ray satellite in 2003, we present 5 Stokes I images and source mode
We present the observational results from the 43-GHz Very Long Baseline Array (VLBA) observations of 124 compact radio-loud active galactic nuclei (AGNs) that were conducted between 2014 November and 2016 May. The typical dimensions of the restoring
We present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 H$beta$ spectra and analyzed the long-term
We present a preliminary analysis of new high resolution radio observations of the nearby TeV blazar Markarian 421 (z=0.031). This study is part of an ambitious multifrequency campaign, with observations in sub-mm (SMA), optical/IR (GASP), UV/X-ray (