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MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN

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MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN

dc.contributor.author	Lister, Matthiew L.
dc.contributor.author	Aller, M. F.
dc.contributor.author	Aller, H. D.
dc.contributor.author	Homan, Daniel C.
dc.contributor.author	Kellermann, K. I.
dc.contributor.author	Kovalev, Yuri Y.
dc.contributor.author	Pushkarev, A. B.
dc.contributor.author	Richards, J. L.
dc.contributor.author	Ros Ibarra, Eduardo
dc.contributor.author	Savolainen, Tuomas
dc.date.accessioned	2017-07-03T15:49:47Z
dc.date.available	2017-07-03T15:49:47Z
dc.date.issued	2013
dc.identifier.citation	Lister, M. L. Aller, M. F. Aller, H. D. Homan, Daniel C. Kellermann, K. I. Kovalev, Y. Y. Pushkarev, A. B. Richards, J. L. Ros Ibarra, Eduardo Savolainen, Tuomas 2013 MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN Astronomical Journal 146 120 1 22
dc.identifier.uri	http://hdl.handle.net/10550/59323
dc.description.abstract	We describe the parsec-scale kinematics of 200 AGN jets based on 15 GHz VLBA data obtained between 1994 Aug 31 and 2011 May 1. We present new VLBA 15 GHz images of these and 59 additional AGN 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 to 16 year interval, ranging from 10º to 150º on the sky, corresponding to intrinsic variations of ∼0.5º to ∼2º. 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 to 12 y), 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 per y), 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 10^26 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.
dc.language.iso	eng
dc.relation.ispartof	Astronomical Journal, 2013, vol. 146, num. 120, p. 1-22
dc.subject	Astrofísica
dc.subject	Astronomia
dc.title	MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN
dc.type	journal article	es_ES
dc.date.updated	2017-07-03T15:49:48Z
dc.identifier.doi	10.1088/0004-6256/146/5/120
dc.identifier.idgrec	086482
dc.rights.accessRights	open access	es_ES