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Title:
MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VII. Blazar Jet Acceleration
Authors:
Homan, D. C.; Kadler, M.; Kellermann, K. I.; Kovalev, Y. Y.; Lister, M. L.; Ros, E.; Savolainen, T.; Zensus, J. A.
Affiliation:
AA(Department of Physics and Astronomy, Denison University, Granville, OH 43023, USA ), AB(Dr. Remeis-Sternwarte Bamberg, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany ; Erlangen Centre for Astroparticle Physics, Erwin-Rommel Str. 1, 91058 Erlangen, Germany ; CRESST/NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA ; Universities Space Research Association, 10211 Wincopin Circle, Suite 500 Columbia, MD 21044, USA ; ), AC(National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA ), AD(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany ; Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow, Russia ; ), AE(Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907, USA ), AF(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany ; Departament d'Astronomia i Astrofísica, Universitat de València, E-46100 Burjassot, València, Spain; ), AG(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany ), AH(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany )
Publication:
The Astrophysical Journal, Volume 706, Issue 2, pp. 1253-1268 (2009). (ApJ Homepage)
Publication Date:
12/2009
Origin:
IOP
ApJ Keywords:
BL Lacertae objects: general, galaxies: active, galaxies: jets, quasars: general, radio continuum: galaxies, surveys
DOI:
10.1088/0004-637X/706/2/1253
Bibliographic Code:
2009ApJ...706.1253H

Abstract

We discuss acceleration measurements for a large sample of extragalactic radio jets from the Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments (MOJAVE) program, which studies the parsec-scale jet structure and kinematics of a complete, flux-density-limited sample of active galactic nuclei (AGNs). Accelerations are measured from the apparent motion of individual jet features or "components" which may represent patterns in the jet flow. We find that significant accelerations are common both parallel and perpendicular to the observed component velocities. Parallel accelerations, representing changes in apparent speed, are generally larger than perpendicular acceleration that represent changes in apparent direction. The trend for larger parallel accelerations indicates that a significant fraction of these changes in apparent speed are due to changes in intrinsic speed of the component rather than changes in direction to the line of sight. We find an overall tendency for components with increasing apparent speed to be closer to the base of their jets than components with decreasing apparent speed. This suggests a link between the observed pattern motions and the underlying flow which, in some cases, may increase in speed close to the base and decrease in speed further out; however, common hydrodynamical processes for propagating shocks may also play a role. About half of the components show "non-radial" motion, or a misalignment between the component's structural position angle and its velocity direction, and these misalignments generally better align the component motion with the downstream emission. Perpendicular accelerations are closely linked with non-radial motion. When observed together, perpendicular accelerations are usually in the correct direction to have caused the observed misalignment.
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