Kinematics of Parsec-scale Jets of Gamma-Ray Blazars at 43 GHz within the VLBA-BU-BLAZAR Program

Svetlana G. Jorstad, Alan P. Marscher, Daria A. Morozova, Ivan S. Troitsky, Iván Agudo, Carolina Casadio, Adi Foord, José L. Gómez, Nicholas R. MacDonald, Sol N. Molina, Anne Lähteenmäki, Joni Tammi, Merja Tornikoski

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We analyze the parsec-scale jet kinematics from 2007 June to 2013January of a sample of γ-ray bright blazars monitored roughlymonthly with the Very Long Baseline Array at 43 GHz. In a total of 1929images, we measure apparent speeds of 252 emission knots in 21 quasars,12 BL Lacertae objects (BLLacs), and 3 radio galaxies, ranging from0.02c to 78c; 21% of the knots are quasi-stationary. Approximatelyone-third of the moving knots execute non-ballistic motions, with thequasars exhibiting acceleration along the jet within 5 pc (projected) ofthe core, and knots in BLLacs tending to decelerate near the core. Usingthe apparent speeds of the components and the timescales of variabilityfrom their light curves, we derive the physical parameters of 120superluminal knots, including variability Doppler factors, Lorentzfactors, and viewing angles. We estimate the half-opening angle of eachjet based on the projected opening angle and scatter of intrinsicviewing angles of knots. We determine characteristic values of thephysical parameters for each jet and active galactic nucleus class basedon the range of values obtained for individual features. We calculatethe intrinsic brightness temperatures of the cores,{T}{{b},{int}}{core}, at all epochs, finding thatthe radio galaxies usually maintain equipartition conditions in thecores, while ∼30% of {T}{{b},{int}}{core}measurements in the quasars and BLLacs deviate from equipartition valuesby a factor >10. This probably occurs during transient eventsconnected with active states. In the Appendix, we briefly describe thebehavior of each blazar during the period analyzed.
Original languageEnglish
Article number98
Number of pages35
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed


  • galaxies: active
  • galaxies: jets
  • techniques: interferometric


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