The jet collimation profile at high resolution in BL Lacertae
| Autor: | Z. R. Weaver, Svetlana G. Jorstad, J. González García, B. Boccardi, Thomas P. Krichbaum, Michael Lindqvist, Jeffrey A. Hodgson, J. A. Zensus, M. Gómez Garrido, Jia-Hui Yang, S. Sanchez, Carolina Casadio, J. Y. Kim, Juha Kallunki, Alan P. Marscher, Nicholas R. MacDonald, Efthalia Traianou |
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| Přispěvatelé: | Institute of Electronic Structure and Laser, Max-Planck-Institut für Radioastronomie, Boston University, Sejong University, Observatorio de Yebes (IGN), Metsähovi Radio Observatory, Chalmers University of Technology, Instituto de Radio Astronomia Milimétrica, Aalto-yliopisto, Aalto University |
| Rok vydání: | 2021 |
| Předmět: |
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
active [Galaxies] Astrophysics::High Energy Astrophysical Phenomena High resolution FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences IRAM 30m telescope law.invention Telescope 03 medical and health sciences high angular resolution [Instrumentation] Observatory law 0103 physical sciences Very-long-baseline interferometry media_common.cataloged_instance European union 010303 astronomy & astrophysics Very Long Baseline Array 030304 developmental biology media_common individual: BL Lacertae [BL Lacertae objects] Physics High Energy Astrophysical Phenomena (astro-ph.HE) 0303 health sciences Astronomy Astronomy and Astrophysics interferometers [Instrumentation] Space and Planetary Science jets [Galaxies] High Energy Physics::Experiment Astrophysics - High Energy Astrophysical Phenomena Fermi Gamma-ray Space Telescope Astrophysics - Cosmology and Nongalactic Astrophysics |
| Zdroj: | Astronomy & Astrophysics |
| DOI: | 10.48550/arxiv.2102.08952 |
| Popis: | Controversial studies on the jet collimation profile of BL Lacertae (BL Lac), the eponymous blazar of BL Lac objects class, complicate the scenario in this already puzzling class of objects. Understanding the jet geometry, in connection with the jet kinematics and the physical conditions in the surrounding medium, is fundamental to better constrain the formation, acceleration and collimation mechanisms in extragalactic jets. With the aim of investigating the jet geometry in the innermost regions of the jet of BL Lac, and solving the controversy, we explore the radio jet in this source, using high resolution millimeter-wave VLBI data. We collect 86GHz GMVA and 43GHz VLBA data to obtain stacked images that we use to infer the jet collimation profile by means of two comparable methods. We analyze the kinematics at 86GHz, and we discuss it in the context of the jet expansion. Finally we consider a possible implication of the Bondi sphere in shaping the different expanding region observed along the jet. We found that the jet in BL Lac expands with an overall conical geometry. A higher expanding rate region is observed between ~5 and 10 pc (de-projected) from the black hole. Such a region is associated with the decrease in brightness usually observed in high-frequency VLBI images of BL Lac. The jet retrieves the original jet expansion around 17 pc, where the presence of a recollimation shock is supported by both the jet profile and the 15GHz kinematics (MOJAVE survey). The change in the jet expansion profile occurring at ~5 pc could be associated with a change in the external pressure profile in correspondence of the Bondi radius (~3.3X10$^5$$R_s$). Comment: 10 pages, 12 figures. Accepted for publication in Astronomy & Astrophysics |
| Databáze: | OpenAIRE |
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