4,138 research outputs found
Multiband polarimetric and total intensity imaging of 3C345
We monitored the superluminal QSO 3C 345 at three epochs during a one-year
period in 1995--1996, observing with the VLBA at 22, 15, 8.4, and 5 GHz. We
imaged the radio source both in total and in polarized intensity. In the images
at 5 and 8.4 GHz, the jet emission is traced up to 20 milliarcseconds (mas)
from the jet core. In the 15 and 22 GHz images, we identify several enhanced
emission regions moving at apparent speeds of 5c. Images of the linear
polarized emission show predominantly an alignment of the electric vector with
the extremely curved jet along the inner part of the high frequency jet. At 5
GHz, the jet shows remarkably strong fractional polarization (m~15%) with the
electric vector perpendicular to the jet orientation.Comment: LaTeX file, 6 pages, 2 figures, needs "elsart" style package To be
published in New Astronomy Reviews, special issue: Proceedings of the 4th
EVN/JIVE VLBI Symposium, Eds. Garrett, M.A., Campbell, R.M., & Gurvits, L.
Is 0716+714 a superluminal blazar?
We present an analysis of new and old high frequency VLBI data collected
during the last 10 years at 5--22 GHz. For the jet components in the mas-VLBI
jet, two component identifications are possible. One of them with
quasi-stationary components oscillating about their mean positions. Another
identification scheme, which formally gives the better expansion fit, yields
motion with for km s Mpc and .
This model would be in better agreement with the observed rapid IDV and the
expected high Lorentz-factor, deduced from IDV.Comment: 2 pages, 3 figures, appears in: Proceedings of the 6th European VLBI
Network Symposium held on June 25th-28th in Bonn, Germany. Edited by: E. Ros,
R.W. Porcas, A.P. Lobanov, and J.A. Zensu
NGC1052 - A study of the pc-scale twin jet
We present results of a VLBA multi-frequency study of the pc-scale twin jet
in NGC1052. We observed this object at epoch 1998.99 with the VLBA at 5, 8.4,
22 and 43 GHz both in total and linearly polarized intensity. The spectral
analysis confirms the necessity of a free-free absorbing medium, obscuring the
innermost part of both jets. At 5 GHz we found a compact linearly polarized
emission region at the base of the eastern jet with a degree of polarization of
1.5%. At higher frequencies there is no evidence for polarization in our data.
A core shift analysis constrains the position of the central engine to ~0.03
pc. The shift rates of the apparent core position with frequency confirm the
strong influence of free-free absorption in conjunction with steep pressure
gradients at the bases of both jets.Comment: Proceedings of the conference "SRT: the impact of large antennas on
Radio Astronomy and Space Science", Cagliari, Italy, 7-10 November 2001, in
press; 6 pages, 5 figures, needs srt_style.st
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