English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report on the acceleration properties of 329 features in 95 blazar jetsfrom the MOJAVE VLBA program. Nearly half the features and three-quarters ofthe jets show significant changes in speed and/or direction. In general,apparent speed changes are distinctly larger than changes in direction,indicating that changes in the Lorentz factors of jet features dominate theobserved speed changes rather than bends along the line of sight. Observedaccelerations tend to increase the speed of features near the jet base,$\lesssim 10-20$ parsecs projected, and decrease their speed at longerdistances. The range of apparent speeds at fixed distance in an individual jetcan span a factor of a few, indicating that shock properties and geometry mayinfluence the apparent motions; however, we suggest that the broad trend of jetfeatures increasing their speed near the origin is due to an overallacceleration of the jet flow out to de-projected distances of order $10^2$parsecs, beyond which the flow begins to decelerate or remains nearly constantin speed. We estimate intrinsic rates of change of the Lorentz factors in thegalaxy frame of order $\dot{\Gamma}/\Gamma \simeq 10^{-3}$ to $10^{-2}$ peryear which can lead to total Lorentz factor changes of a factor of a few on thelength scales observed here. Finally, we also find evidence for jet collimationat projected distances of $\lesssim 10$ parsecs in the form of the non-radialmotion and bending accelerations that tend to better align features with theinner jet.

MOJAVE XII: Acceleration and Collimation of Blazar Jets on Parsec Scales