Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Jet Kinematics from Bimonthly Monitoring with the Very Long Baseline Array
| Autor: | James R. Forster, Timothy V. Cawthorne, Svetlana G. Jorstad, Paul S. Smith, Walter Kieran Gear, Matthew L. Lister, Jamie Stevens, A. M. Stirling, Alan P. Marscher, José L. Gómez, E. Ian Robson |
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| Rok vydání: | 2005 |
| Předmět: |
Physics
Superluminal motion Active galactic nucleus Radio galaxy Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) FOS: Physical sciences Astronomy and Astrophysics Quasar Astrophysics Polarization (waves) symbols.namesake Wavelength Space and Planetary Science symbols Doppler effect Very Long Baseline Array |
| Zdroj: | The Astronomical Journal. 130:1418-1465 |
| ISSN: | 1538-3881 0004-6256 |
| DOI: | 10.1086/444593 |
| Popis: | We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7 mm at 17 epochs from 1998 March to 2001 April. At some epochs the images are accompanied by nearly simultaneous polarization measurements at 3 mm, 1.35/0.85 mm, and optical wavelengths. Here we analyze the 7 mm images to define the properties of the jets of two radio galaxies, five BL Lac objects, and eight quasars on angular scales $\gtrsim 0.1$ milliarcseconds. We determine the apparent velocities of 106 features in the jets; for many of the features we derive Doppler factors using a new method based on comparison of timescale of decline in flux density with the light-travel time across the emitting region. This allows us to estimate the Lorentz factors, intrinsic brightness temperatures, and viewing angles of 73 superluminal knots, as well as the opening angle of the jet for each source. We analyze the derived physical parameters of the jets. In nine sources we detect statistically meaningful deviations from ballistic motion, with the majority of components accelerating with distance from the core. In six sources we identify jet features with characteristics of trailing shocks that form behind the primary strong perturbations in jet simulations. The apparent speeds of these components increase with distance from the core suggesting an acceleration of the underlying jet. Comment: 100 pages, 44 figures, accepted for publication in AJ. This version does not contain figures 1-15,17(sequences of the images) due to very large size of the figures. The complete version (7mm_ms.ps) can be found at the website: www.bu.edu/blazars/multi.html |
| Databáze: | OpenAIRE |
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