J/A+A/484/119 Multi-epoch VLBI survey of CJF sources (Britzen+, 2008)
A multi-epoch VLBI Survey of the kinematics of Caltech-Jodrell Bank
flat-spectrum sources.
Britzen S., Vermeulen R.C., Campbell R.M., Taylor G.B., Pearson T.J.,
Readhead A.C.S., Xu W., Browne I.W., Henstock D.R., Wilkinson P.
<Astron. Astrophys. 484, 119 (2008)>
=2008A&A...484..119B 2008A&A...484..119B
ADC_Keywords: Active gal. nuclei ; BL Lac objects ; Galaxies, radio ;
Radio sources ; VLBI
Keywords: instrumentation: interferometers - galaxies: active -
galaxies: quasars: general - galaxies: jets -
galaxies: BL Lacertae objects: general
Abstract:
This is the second in a series of papers presenting VLBI observations
of the 293 Caltech-Jodrell Bank Flat-spectrum (hereafter CJF) sources
and their analysis. We obtain a consistent motion dataset large enough
to allow the systematic properties of the population to be studied. We
present detailed kinematic analysis of the complete flux-density
limited CJF survey. We computed 2-D kinematic models based on the
optimal model-fitting parameters of multi-epoch VLBA observations.
This allows us to calculate not only radial, but also orthogonal
motions, and thus to study curvature and acceleration. Statistical
tests of the motions measured and their reliability were performed.
A correlation analysis between the derived apparent motions,
luminosities, spectral indices, and core dominance and the resulting
consequences is described. With at least one velocity in each of the
237 sources, this sample is much larger than any available before, so
it allows a meaning ful statistical investigation of apparent motions
and any possible correlations with other parameters in AGN jets. The
main results to emerge are as follows:
* In general motions are not consistent with a single uniform velocity
applicable to all components along a jet.
* We find a slight trend towards a positive outward acceleration and
also adduce some evidence for greater acceleration in the innermost
regions.
* We find a lack of fast components at physical distances less than a
few pc from the reference feature.
* Only ∼4% of the components from galaxies and <2% of those
from quasars undergo large bends i.e. within 15° of ±90°.
* The distribution of radial velocities shows a broad distribution of
velocities (apparent velocities up to 30c). Fifteen percent of the
best-sampled jet components exhibit low velocities that may need to
be explained in a different manner to the fast motions.
* Some negative superluminal motions are seen, and in 15 cases (6%)
these are definitely significant.
* We find a strong correlation between the 5 GHz luminosity and the
apparent velocity.
* The CJF galaxies, on average, show slower apparent jet-component
velocities than the quasars.
* The mean velocity in the VLBA 2cm survey (Kellermann et al. 2004)
is substantially higher than in the CJF survey, the ratio could be
roughly a factor of 1.5-2.
This supports the observed trend toward increasing apparent velocity
with in creasing observing frequency. This AGN survey provides the
basis for any statistical analysis of jet and jet-component
properties.
Description:
The results of the kinematic modeling for all 779 components from
sources participating in the proper-motion analysis are listed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 72 266 Source list
tablec1.dat 188 779 The kinematic properties of 779 AGN-components
fig/* . 798 Kinematic modeling figures in PostScript
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See also:
J/A+A/472/763 : Multi-epoch VLBI survey of CJF sources (Britzen+, 2007)
J/A+A/476/759 : X-ray properties of AGN from the CJF sample (Britzen+, 2007)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name IAU-name of the source HHMM+DDd (B1950),
CJF BHHMM+DDd in Simbad
10- 28 A19 --- Name2000 Name with J2000 position
31- 43 A13 ---- FileNameR Image name of pmtot, pmr and pmphi as function
of radial distance from the core,
in subdirectory fig
45- 57 A13 ---- FileNameT Image name x and y of each component as a
function of time, in subdirectory fig (1)
59- 72 A14 ---- FileNameXY Image name of positions of all components at
all epochs, in subdirectory fig (2)
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Note (1): For each component, a "stationary" dotted line is plotted for
reference.
Note (2): The components are color-coded and the epochs are represented by
different plotting symbols. The modeled positions at each epoch are
shown in small black symbols.
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Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name IAU-name of the source HHMM+DDd (B1950),
CJF BHHMM+DDd in Simbad
10- 19 A10 --- Class Optical classification (1)
20- 21 A2 --- l_z [≥] Limit flag on z
22- 26 F5.3 --- z ? Redshift, see details in paper
27 A1 --- u_z [?] Uncertainty flag on z
29- 31 A3 --- Comp Jet-component identification (2)
33 I1 --- q [1/3] Quality class (3)
35 I1 --- NDet Number of times this component has been
detected
37- 40 F4.2 yr Span Time span from the first to the last detection
42- 51 F10.4 d Epoch Reference epoch -2400000
53- 59 F7.3 mas X0 Component position at the reference epoch in
rectangular X-coordinate
61- 65 F5.3 mas e_X0 ? rms uncertainty on X0 (4)
67- 73 F7.3 mas Y0 Component position at the reference epoch in
rectangular Y-coordinate
75- 79 F5.3 mas e_Y0 ? rms uncertainty on Y0 (4)
81- 86 F6.3 mas/yr pmX Proper motion components in X
88- 92 F5.3 mas/yr e_pmX ? rms uncertainty on pmX (4)
94- 99 F6.3 mas/yr pmY Proper motion components in Y
101-105 F5.3 mas/yr e_pmY ? rms uncertainty on pmY (4)
107-112 F6.3 mas/yr pmr Radial proper motion component
114-118 F5.3 mas/yr e_pmr ? rms uncertainty on pmr (4)
120-125 F6.3 mas/yr pmphi Orthogonal proper motion component
127-131 F5.3 mas/yr e_pmphi ? rms uncertainty on pmphi (4)
133-137 F5.3 mas/yr pmtot Total proper motion, calculated from pmx, pmy
139-143 F5.3 mas/yr e_pmtot ? rms uncertainty on pmtot (4)
145-151 F7.3 c betar ? Radial apparent velocity
153-158 F6.3 c e_betar ? rms uncertainty on betar (4)
160-166 F7.3 c betaphi ? Orthogonal apparent velocity
168-173 F6.3 c e_betaphi ? rms uncertainty on betaphi (4)
175-181 F7.3 c betatot ? Total apparent velocity
183-188 F6.3 c e_betatot ? rms uncertainty on betatot (4)
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Note (1): Optical classification as follows:
Q = quasar
B = BL Lac object
G = galaxy
U = unclassified
Note (2): Jet-component identification as:
C plus a number increasing with ordinal separation from the core
CC in case of counter-jet denotes a counter-jet component
Note (3): Quality flag is 1 for best to 3 for suffers from some problems
in identification
Note (4): Components that have observations at only two epochs do not have
an associated uncertainty ; with no degrees of freedom in the fit for
the kinematic model (four constraints and four unknowns), the scaling
to ∼chi=1 is ill-defined.
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Acknowledgements:
Silke Britzen, sbritzen (at)mpifr-bonn.mpg.de
(End) Silke Britzen [MPIfR, Germany], Patricia Vannier [CDS] 09-Apr-2008