MOJAVE: XVIII. Kinematics and Inner Jet Evolution of Bright Radio-Loud Active Galaxies

Abstract

We have analyzed the parsec-scale jet kinematics of 447 bright radio-loud AGN, based on 15 GHz VLBA data obtained between 1994 August 31 and 2019 August 4. We present new total intensity and linear polarization maps obtained between 2017 January 1 to 2019 August 4 for 143 of these AGN. We tracked 1923 bright features for five or more epochs in 419 jets. A majority (60%) of the well-sampled jet features show either accelerated or non-radial motion. In 47 jets there is at least one non-accelerating feature with an unusually slow apparent speed. Most of the jets show variations of 10 • to 50 • in their inner jet position angle (PA) over time, although the overall distribution has a continuous tail out to 200 • . AGN with SEDs peaked at lower frequencies tend to have more variable PAs, with BL Lacs being less variable than quasars. The Fermi LAT gamma-ray associated AGN also tend to have more variable PAs than the non-LAT AGN in our sample. We attribute these trends to smaller viewing angles for the lower spectral peaked and LAT-associated jets. We identified 13 AGN where multiple features emerge over decade-long periods at systematically increasing or decreasing PAs. Since the ejected features do not fill the entire jet cross-section, this behavior is indicative of a precessing flow instability near the jet base. Although some jets show indications of oscillatory PA evolution, we claim no bona fide cases of periodicity since the fitted periods are comparable to the total VLBA time coverage.

PKS 1424+240: yet another masquerading BL Lac object as a possible IceCube neutrino source

“…close to the equipartition value (∼5 × 10 10 K: Readhead 1994) and therefore indicative of a modest Doppler boosting. This is also supported by proper motion measurements, revealing low apparent speeds of 𝑣 app /𝑐 ≡ 𝛽 app = 2.83 ± 0.89 (Lister et al 2019) and 1.07 ± 0.14 (Lister et al 2021) for PKS 1424+240 and TXS 0506+056 respectively. FSRQs, especially the 𝛾-ray powerful ones, are instead characterized by median core 𝑇 B approaching and often exceeding the inverse Compton catastrophe limit 5 due to strong Doppler boosting (Kovalev et al 2009), as well as by much higher maximum apparent speeds (𝛽 app ∼ 10 − 30, 5 The inverse Compton catastrophe is the rapid cooling through inverse Compton scattering of a synchrotron-emitting region, which implies a threshold temperature ∼ 10 12 K (Kellermann, Pauliny-Toth, & Williams 1969).…”

Flare echos from relaxation shocks in perturbed relativistic jets

“…In this section, we present two further radio galaxies showing signs of the presence of trailing components in the core separation vs time plot, in the form of "fork events" connected to stationary knots. We use the MOJAVE database maintained by the MOJAVE team (Lister et al 2018(Lister et al , 2021.…”

“…While several of these mechanisms may account for flaring events in different sources, the scenarios evoking internal shocks can provide a straightforward connection between time-dependent very-long-baseline interferometry (VLBI) data, which probe the structure of nearby relativistic jets, and MWL flares. VLBI radio observations have revealed both moving and quasi-stationary features in different classes of AGNs (Lister et al 2018(Lister et al , 2021. These bright "radio knots" have been seen from the radio to the millimeter band (Lister et al 2009;Perlman et al 1999;Britzen et al 2010;Fromm et al 2011Fromm et al , 2013aJorstad et al 2013;Hervet et al 2016), with counterparts up to the X-ray band in the most nearby sources (Marshall et al 2002;Wilson & Yang 2002).…”

“…This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d'Avenir supervised by the Agence Nationale pour la Recherche. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al 2018(Lister et al , 2021.…”

One Source, Two Source(s): Ribs and Tethers

“…Pulsed/varying jets? Temporal variability of flux and structure in jets is well-studied on pc-scales (Lister et al [14]). At the other extreme, episodic jet activity has been proposed to explain much larger scale structures in double-double radio galaxies, and the curious multiple structures in a spiral radio galaxy (Sirothia et al [22] ).…”