MOJAVE. X. PARSEC-SCALE JET ORIENTATION VARIATIONS AND SUPERLUMINAL MOTION IN ACTIVE GALACTIC NUCLEI

By M. Lister, M. Aller, H. Aller, D. Homan, K. Kellermann, Y. Kovalev, A. Pushkarev, J. Richards, E. Ros, T. Savolainen. 2013

342 citations recorded by the source corpus.

We describe the parsec-scale kinematics of 200 active galactic nucleus (AGN) jets based on 15 GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2011 May 1. We present new VLBA 15 GHz images of these and 59 additional AGNs from the MOJAVE and 2 cm Survey programs. Nearly all of the 60 most heavily observed jets show significant changes in their innermost position angle over a 12–16 yr interval, ranging from 10° to 150° on the sky, corresponding to intrinsic variations of ∼0.°5 to ∼2°. The BL Lac jets show smaller variations than quasars. Roughly half of the heavily observed jets show systematic position angle trends with time, and 20 show indications of oscillatory behavior. The time spans of the data sets are too short compared to the fitted periods (5–12 yr), however, to reliably establish periodicity. The rapid changes and large jumps in position angle seen in many cases suggest that the superluminal AGN jet features occupy only a portion of the entire jet cross section and may be energized portions of thin instability structures within the jet. We have derived vector proper motions for 887 moving features in 200 jets having at least five VLBA epochs. For 557 well-sampled features, there are sufficient data to additionally study possible accelerations. We find that the moving features are generally non-ballistic, with 70% of the well-sampled features showing either significant accelerations or non-radial motions. Inward motions are rare (2% of all features), are slow (<0.1 mas yr−1), are more prevalent in BL Lac jets, and are typically found within 1 mas of the unresolved core feature. There is a general trend of increasing apparent speed with distance down the jet for both radio galaxies and BL Lac objects. In most jets, the speeds of the features cluster around a characteristic value, yet there is a considerable dispersion in the distribution. Orientation variations within the jet cannot fully account for the dispersion, implying that the features have a range of Lorentz factor and/or pattern speed. Very slow pattern speed features are rare, comprising only 4% of the sample, and are more prevalent in radio galaxy and BL Lac jets. We confirm a previously reported upper envelope to the distribution of speed versus beamed luminosity for moving jet features. Below 1026 W Hz−1 there is a fall-off in maximum speed with decreasing 15 GHz radio luminosity. The general shape of the envelope implies that the most intrinsically powerful AGN jets have a wide range of Lorentz factors up to ∼40, while intrinsically weak jets are only mildly relativistic.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2f4b47b2f0e2ae9a6b4274076644363c72795d89

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In Astronomy and Astrophysics

1. Y. Kovalev
2. M. Lister
3. T. Savolainen
4. A. Marscher
5. A. Pushkarev
6. A. Lobanov
7. S. Komossa
8. J. Zensus

In Nuclear and High Energy Physics

1. Y. Kovalev
2. A. Marscher
3. M. Lister
4. T. Savolainen
5. A. Pushkarev
6. A. Lobanov
7. Luigi Foschini
8. J. Zensus

Citations in the corpus

• Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations (2017, background): “Disc tilt has been invoked to explain quasiperiodic oscillations (QPOs) in BH systems (Stella & Vietri 1998; Ingram, Done & Fragile 2009) and variability in the jet orientation (Agudo et al. 2012; Stone & Loeb 2012; Lister et al. 2013, 2016; Tchekhovskoy et al. 2014).”
• MOJAVE. XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-scale AGN Jets from 1996 to 2017 (2017, background): “More details on individual objects and their total intensity evolution can be found in other papers in this series (e.g., Lister et al. 2013, 2016).”
• The Fermi blazar sequence (2017, background): “On the other hand, direct VLBI and VLBA measurements of superluminal knots in blazars (Jorstad et al. 2001; Lister et al. 2013), and modelling (Ghisellini & Tavecchio 2015) do not find strong differences in the bulk Lorentz factors of BL Lacs and FSRQs.”
• THE THIRD CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE (2015, background): “…e is av ai la bl e in its en tir et y in m ac hi ne -r ea da bl e fo rm .) superluminal motions measured in their parsec-scale jets, indicating that they are the most well-aligned sources to our line of sight among the SSRQs in the 3CRR (e.g., Wilkinson et al. 1991; Hough 2013; Lister et al. 2013).”
• Properties of flat-spectrum radio-loud Narrow-Line Seyfert 1 Galaxies (2014, methodology): “15 GHz data are from the the MOJAVE database (Lister et al. 2009, 2013)3.”
• Detection of significant cm to sub-mm band radio and γ-ray correlated variability in Fermi bright blazars (2014, background): “Recent studies show, however, that the dispersion of apparent speeds in a given jet is moderate and jet speeds cluster around a characteristic value (Lister et al. 2013).”
• MOJAVE. XIII. PARSEC-SCALE AGN JET KINEMATICS ANALYSIS BASED ON 19 YEARS OF VLBA OBSERVATIONS AT 15 GHz (2016, methodology): “We have excluded from our kinematics analysis 48 MOJAVE AGNs we previously analyzed in Lister et al. (2013), since we are currently gathering additional VLBA epochs on them.”
• An Accurate Flux Density Scale from 50 MHz to 50 GHz (2016, background): “VLBA observations of this component by Lister et al. (2013) show a highly superluminal jet (β ∼ 13.1) emanating to the NW from the core.”
• Kinematics of Parsec-scale Jets of Gamma-Ray Blazars at 43 GHz within the VLBA-BU-BLAZAR Program (2017, methodology): “Analysis of parsec-scale jet behavior at longer wavelengths during the same period of time can be found in Britzen et al. (2013); Lister et al. (2013, 2016).”
• Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii (2016, background): “Between 1995 and 2010, the jet in M 87 was regularly observed as part of the MOJAVE project (Lister et al. 2009, 2013).”
• A hadronic origin for ultra-high-frequency-peaked BL Lac objects (2014, background): “…of the plasma blob and/or a very small viewing angle with respect to the jet axis and could thus be difficult to reconcile with radio observations of the movement of knots inside jets (see e.g. Lister et al. 2013) or with the statistics of observed blazars and radio-galaxies (Henri & Saugé 2006).”