TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet

Mueller C, Kadler M, Ojha R, Perucho M, Großberger C, Ros E, Wilms J, Blanchard J, Boeck M, Carpenter B, Dutka M, Edwards PG, Hase H, Horiuchi S, Kreikenbohm A, Lovell JEJ, Markowitz A, Phillips C, Ploetz C, Pursimo T, Quick J, Rothschild R, Schulz R, Steinbring T, Stevens J, Truestedt J, Tzioumis AK (2014)

Publication Status: Published

Publication Type: Journal article

Publication year: 2014

Journal

Publisher: EDP SCIENCES S A

Book Volume: 569

Article Number: ARTN A115

DOI: 10.1051/0004-6361/201423948

Abstract

Context. Centaurus A (Cen A) is the closest radio-loud active galactic nucleus. Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on milliarcsecond scales, providing essential information for jet emission and propagation models.Aims. In the framework of the TANAMI monitoring, we investigate the kinematics and complex structure of Cen A on subparsec scales. We have been studying the evolution of the central parsec jet structure of CenA for over 3.5 years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high-energy flux with jet ejection events. Cen A is an exceptional laboratory for such a detailed study because its proximity translates to unrivaled linear resolution, where one milliarcsecond corresponds to 0.018 pc.Methods. As a target of the southern-hemisphere VLBI monitoring program TANAMI, observations of CenA are done approximately every six months at 8.4 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, New Zealand, and South Africa, complemented by quasi-simultaneous 22.3 GHz observations.Results. The first seven epochs of high-resolution TANAMI VLBI observations at 8.4 GHz of CenA are presented, resolving the jet on (sub-) milliarcsecond scales. They show a differential motion of the subparsec scale jet with significantly higher component speeds farther downstream where the jet becomes optically thin. We determined apparent component speeds within a range of 0 : 1 c to 0 : 3 c and identified long-term stable features. In combination with the jet-to-counterjet ratio, we can constrain the angle to the line of sight to theta similar to 12 degrees-45 degrees.Conclusions. The high-resolution kinematics are best explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. On top of the underlying, continuous flow, TANAMI observations clearly resolve individual jet features. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and circumfluent jet behavior. We propose a jet-star interaction scenario to explain this appearance. The comparison of jet ejection times to high X-ray flux phases yields a partial overlap of the onset of the X-ray emission and increasing jet activity, but the limited data do not support a robust correlation.

Authors with CRIS profile

Involved external institutions

Julius-Maximilians-Universität Würzburg Germany (DE) University of València / Universitat de València Spain (ES) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) University of California, San Diego United States (USA) (US) Bundesamt für Kartographie und Geodäsie (BKG) / Federal Agency for Cartography and Geodesy Germany (DE) Catholic University of America United States (USA) (US) Hartebeesthoek Radio Astronomy Observatory (HartRAO) South Africa (ZA) Universidad de Concepcion Chile (CL) Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia (AU) National Aeronautics and Space Administration (NASA) United States (USA) (US) Nordic Optical Telescope Spain (ES) University of Tasmania (UTAS) Australia (AU)

How to cite

APA:

Mueller, C., Kadler, M., Ojha, R., Perucho, M., Großberger, C., Ros, E.,... Tzioumis, A.K. (2014). TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet. Astronomy & Astrophysics, 569. https://dx.doi.org/10.1051/0004-6361/201423948

MLA:

Mueller, C., et al. "TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet." Astronomy & Astrophysics 569 (2014).

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