Special Issue "Particle Acceleration Processes in Astrophysical Jets"

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (31 August 2019).

Special Issue Editors

Assoc. Prof. Dr. Bidzina Kapanadze
E-Mail Website
Guest Editor
Abastumani Astrophysical Observatory, Ilia State University, 0162 Tbilisi, Georgia
Interests: BL Lacertae ; relativistic jets; supermassive black hole; Fermi acceleration; nonthermal emission; relativistic shock waves; X-ray astronomy; gamma-ray astronomy; optical astronomy; blazar multifrequency variability
Prof. Philip Hughes
E-Mail Website
Guest Editor
Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
Interests: active galactic nuclei, blazars, black holes, relativistic jets

Special Issue Information

Dear Colleagues,

Astrophysical jets, the collimated outflows associated with matter accretion onto compact objects, represent one of the most extreme phenomena in the Universe. They have been observed from a variety of cosmic sources, from protostars to distant galaxies, and often determine the major observational features of the parent object. The jet phenomenon appears to be common wherever mass accretion onto a central object occurs. In many cases, the bulk motion of the jet plasma is close to the speed of light, so relativistic effects play an important role in the physical processes in these outflows. Jets become relativistic in the case of accretion onto compact objects, such as neutron stars or black holes, both in Galactic systems and extragalactic systems. The detection of astrophysical jets and our understanding of their physical nature has been closely related to the development of multiwavelength instruments, and improved methods of simulation. However, we still need much effort to make progress in our understanding of the many fundamental aspects of jet physics that are still poorly understood and constrained: the mechanisms of jet launching andacceleration, the connection between these processes and those operating in accretion discs; the physics responsible for jet collimation over tens of thousands to even millions of Schwarzschild radii of the central putative black holes; the role of magnetic fields and reconnection;  the matter content of jets; the location of the region accelerating particles to TeV-PeV energy, and, possibly, even to EeV energies; the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes.

This Issue reviews our current understanding of the particle acceleration processes at work in the jets of various extreme Galactic and extragalactic objects: protostars, X-ray binaries, microquasars, Fermi bubbles (as relics of Seyfert-type active Galactic nuclei), blazars, radio galaxies, and gamma-ray bursts. It emphasizes unresolved problems, and the importance of multiwavelength monitoring and high-resolution simulations for insight into the physical processes operating in the jets of various objects over a range of distances from the central engine.

Prof. Bidzina Kapanadze
Prof. Philip Hughes
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Jets: relativistic
  • collimation
  • particle acceleration
  • active galactic nuclei
  • microquasars
  • GRBs
  • Seyfert galaxies
  • blazars
  • quasars
  • X-ray binaries

Published Papers (2 papers)

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Review

Open AccessReview
Relativistic Jets in Gamma-Ray-Emitting Narrow-Line Seyfert 1 Galaxies
Galaxies 2019, 7(4), 87; https://doi.org/10.3390/galaxies7040087 - 07 Nov 2019
Abstract
Before the launch of the Fermi Gamma-ray Space Telescope satellite only two classes of active galactic nuclei (AGN) were known to generate relativistic jets and thus to emit up to the γ -ray energy range: blazars and radio galaxies, both hosted in giant [...] Read more.
Before the launch of the Fermi Gamma-ray Space Telescope satellite only two classes of active galactic nuclei (AGN) were known to generate relativistic jets and thus to emit up to the γ -ray energy range: blazars and radio galaxies, both hosted in giant elliptical galaxies. The discovery by the Large Area Telescope (LAT) on-board the Fermi satellite of variable γ -ray emission from a few radio-loud narrow-line Seyfert 1 galaxies (NLSy1) revealed the presence of an emerging third class of AGN with powerful relativistic jets. Considering that NLSy1 are usually hosted in late-type galaxies with relatively small black hole masses, this finding opened new challenging questions about the nature of these objects, the disc/jet connection, the emission mechanisms at high energies, and the formation of relativistic jets. In this review, I will discuss the broad-band properties of the γ -ray-emitting NLSy1 included in the Fourth Fermi LAT source catalog, highlighting major findings and open questions regarding jet physics, black hole mass estimation, host galaxy and accretion process of these sources in the Fermi era. Full article
(This article belongs to the Special Issue Particle Acceleration Processes in Astrophysical Jets)
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Open AccessReview
An Introduction to Particle Acceleration in Shearing Flows
Galaxies 2019, 7(3), 78; https://doi.org/10.3390/galaxies7030078 - 10 Sep 2019
Cited by 3
Abstract
Shear flows are ubiquitously present in space and astrophysical plasmas. This paper highlights the central idea of the non-thermal acceleration of charged particles in shearing flows and reviews some of the recent developments. Topics include the acceleration of charged particles by microscopic instabilities [...] Read more.
Shear flows are ubiquitously present in space and astrophysical plasmas. This paper highlights the central idea of the non-thermal acceleration of charged particles in shearing flows and reviews some of the recent developments. Topics include the acceleration of charged particles by microscopic instabilities in collisionless relativistic shear flows, Fermi-type particle acceleration in macroscopic, gradual and non-gradual shear flows, as well as shear particle acceleration by large-scale velocity turbulence. When put in the context of jetted astrophysical sources such as Active Galactic Nuclei, the results illustrate a variety of means beyond conventional diffusive shock acceleration by which power-law like particle distributions might be generated. This suggests that relativistic shear flows can account for efficient in-situ acceleration of energetic electrons and be of relevance for the production of extreme cosmic rays. Full article
(This article belongs to the Special Issue Particle Acceleration Processes in Astrophysical Jets)
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