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Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155–304

Lucchini, M. and Markoff, S. and Crumley, P. and Krauß, F. and Connors, R. M. T. (2019) Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155–304. Monthly Notices of the Royal Astronomical Society, 482 (4). pp. 4798-4812. ISSN 0035-8711. doi:10.1093/mnras/sty2929.

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Supermassive black holes can launch powerful jets which can be some of the most luminous multiwavelength sources; decades after their discovery their physics and energetics are still poorly understood. The past decade has seen a dramatic improvement in the quality of available data, but despite this improvement the semi-analytical modelling of jets has advanced slowly: simple one-zone models are still the most commonly employed method of interpreting data, in particular for active galactic nucleus (AGN) jets. These models can roughly constrain the properties of jets but they cannot unambiguously couple their emission to the launching regions and internal dynamics, which can be probed with simulations. However, simulations are not easily comparable to observations because they cannot yet self-consistently predict spectra. We present an advanced semi-analytical model which accounts for the dynamics of the whole jet, starting from a simplified parametrization of relativistic magnetohydrodynamics in which the magnetic flux is converted into bulk kinetic energy. To benchmark the model, we fit six quasi-simultaneous, multiwavelength spectral energy distributions of the BL Lac PKS 2155–304 obtained by the TANAMI (Tracking Active Galactic Nuclei with Austral Milliarc-second Interferometry) program, and we address the degeneracies inherent to such a complex model by employing a state-of-the-art exploration of parameter space, which so far has been mostly neglected in the study of AGN jets. We find that this new approach is much more effective than a single-epoch fit in providing meaningful constraints on model parameters.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Markoff, S.0000-0001-9564-0876
Crumley, P.0000-0002-5355-7158
Krauß, F.0000-0001-6191-1244
Connors, R. M. T.0000-0002-8908-759X
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 October 25. Received 2018 October 18; in original form 2018 July 6. Published: 30 October 2018. The authors of this manuscript would like to thank the suggestions of the anonymous referee for careful reading and useful comments. ML and SM are thankful for support from an NWO (Netherlands Organization for Scientific Research) VICI award, grant no. 639.043.513. FK acknowledges funding from the European Union’s Horizon 2020 research and innovation program under grant agreement no. 653477. ML thanks Phil Uttley for insightful discussions on the variability of accretion flows. This research has made use of ISIS functions (ISISscripts) provided by the Erlangen Center for Particle Astrophysics, the Remeis observatory and the Massachussets Institute for Technology (
Funding AgencyGrant Number
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)639.043.513
European Research Council (ERC)653477
Subject Keywords:radiation mechanisms: non-thermal – BL Lacertae objects: individual: PKS 2155−304 – gamma-rays: galaxies
Issue or Number:4
Record Number:CaltechAUTHORS:20190411-155231146
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Official Citation:M Lucchini, S Markoff, P Crumley, F Krauß, R M T Connors, Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155–304, Monthly Notices of the Royal Astronomical Society, Volume 482, Issue 4, February 2019, Pages 4798–4812,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94673
Deposited By: Tony Diaz
Deposited On:12 Apr 2019 02:57
Last Modified:16 Nov 2021 17:06

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