Abstrakti
We discuss the jet kinematics of a complete flux-density-limited sample
of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year
program to investigate the structure and evolution of parsec-scale jet
phenomena. Our analysis is based on new 2 cm Very Long Baseline Array
(VLBA) images obtained between 2002 and 2007, but includes our
previously published observations made at the same wavelength, and is
supplemented by VLBA archive data. In all, we have used 2424 images
spanning the years 1994-2007 to study and determine the motions of 526
separate jet features in 127 jets. The data quality and temporal
coverage (a median of 15 epochs per source) of this complete AGN jet
sample represent a significant advance over previous kinematics surveys.
In all but five AGNs, the jets appear one-sided, most likely the result
of differential Doppler boosting. In general, the observed motions are
directed along the jet ridge line, outward from the optically thick core
feature. We directly observe changes in speed and/or direction in one
third of the well-sampled jet components in our survey. While there is
some spread in the apparent speeds of separate features within an
individual jet, the dispersion is about three times smaller than the
overall dispersion of speeds among all jets. This supports the idea that
there is a characteristic flow that describes each jet, which we have
characterized by the fastest observed component speed. The observed
maximum speed distribution is peaked at ~10c, with a tail that extends
out to ~50c. This requires a distribution of intrinsic Lorentz factors
in the parent population that range up to ~50. We also note the presence
of some rare low-pattern speeds or even stationary features in otherwise
rapidly flowing jets that may be the result of standing re-collimation
shocks, and/or a complex geometry and highly favorable Doppler factor.
Alkuperäiskieli | Englanti |
---|---|
Sivut | 1874-1892 |
Julkaisu | Astronomical Journal |
Vuosikerta | 138 |
Numero | 6 |
DOI - pysyväislinkit | |
Tila | Julkaistu - 2009 |
OKM-julkaisutyyppi | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä |