Stellar and galactic jets: theoretical issues

1986 ◽  
Vol 64 (4) ◽  
pp. 362-368 ◽  
Author(s):  
Arieh Königl
Keyword(s):  
Active Galactic Nuclei ◽  
Molecular Cloud ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Observational Constraints ◽  
Stellar Objects ◽  
Physical Mechanisms ◽  
Stellar Jets ◽  
Propagation Effects ◽  
Theoretical Issues

Theoretical issues pertaining to the modelling of jets in young stellar objects and in active galactic nuclei are reviewed. The strong morphological similarities between these two types of sources are emphasized, and observational constraints on the basic physical mechanisms that may be responsible for the jet phenomenon are outlined. Particular attention is given to the "momentum-discharge problem" in molecular-cloud outflows and to its possible resolution in terms of a centrifugally driven magnetohydrodynamic wind from an accretion disk. In addition, various propagation effects are discussed, and the relevance to stellar jets of the de Laval collimation mechanism and of the accelerated-clump model for emission knots is assessed. The review concludes with a brief list of potentially useful observational tests.

scholarly journals Water fountains: bipolar fast stellar jets traced by water vapor maser emission

2012 ◽  
Vol 8 (S290) ◽  
pp. 227-228
Author(s):  
Hiroshi Imai
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Asymptotic Giant Branch ◽  
Young Stellar Objects ◽  
Agb Stars ◽  
Stellar Objects ◽  
Stellar Jets ◽  
The Masses ◽  
Host Stars ◽  
Maser Sources

AbstractHighly collimated, bipolar fast jets are found in asymptotic giant branch (AGB) and post-AGB stars as well as in active galactic nuclei and young stellar objects. It is still unclear how to launch such jets from dying stars that were originally spherically symmetric. Exploration of the stellar jet evolution is also expected to probe its role in shaping a planetary nebula. Interestingly, some of stellar H2O maser sources — water fountains — exhibit stellar jets with spatially and kinematically high collimation in the earliest phase (<1000 years) of the jet evolution. Such water fountains have been identified in 14 sources to date. We have recently conducted interferometric (VLBA, EVN, VERA, VLA) maser and the single-dish (ASTE) CO J = 3 → 2 line observations of the water fountains. They have revealed a typical dynamical age (< 100 yr) and the detailed kinematical structures of the water fountains, possibility of the coexistence of “equatorial flows”, and their locations and kinematics in the Milky Way. Based on these results, the masses and evolutionary statuses of the host stars are also estimated.

scholarly journals MAGNETIC FIELD EFFECTS NEAR THE LAUNCHING REGION OF ASTROPHYSICAL JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 729-739 ◽  
Author(s):  
E. M. DE GOUVEIA DAL PINO ◽  
G. KOWAL ◽  
L. H. S. KADOWAKI ◽  
P. PIOVEZAN ◽  
A. LAZARIAN
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Magnetic Energy ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Magnetic Field Effects ◽  
Astrophysical Jets ◽  
Stellar Objects ◽  
Fundamental Properties

One of the fundamental properties of astrophysical magnetic fields is their ability to change topology through reconnection and in doing so, to release magnetic energy, sometimes violently. In this work, we review recent results on the role of magnetic reconnection and associated heating and particle acceleration in jet/accretion disk systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs).

RADIATIVE PROCESSES IN JETS

2010 ◽  
Vol 19 (06) ◽  
pp. 659-669 ◽  
Author(s):  
GABRIELA S. VILA
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Electromagnetic Spectrum ◽  
Physical Processes ◽  
Energy Distributions ◽  
Stellar Objects ◽  
Radiative Processes ◽  
Relativistic Particles

Relativistic jets and collimated outflows are ubiquitous phenomena in astrophysical settings, from young stellar objects up to Active Galactic Nuclei. The observed emission from some of these jets can cover the whole electromagnetic spectrum, from radio to gamma-rays. The relevant features of the spectral energy distributions depend on the nature of the source and on the characteristics of the surrounding environment. Here the author reviews the main physical processes that command the interactions between populations of relativistic particles locally accelerated in the jets, with matter, radiation and magnetic fields. Special attention is given to the conditions that lead to the dominance of the different radiative mechanisms. Examples from various types of sources are used to illustrate these effects.

The Formation of Astrophysical Jets

1997 ◽  
Vol 163 ◽  
pp. 845-866 ◽  
Author(s):  
Mario Livio
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Astrophysical Jets ◽  
Stellar Objects ◽  
X Ray ◽  
Astrophysical Objects ◽  
Low Mass ◽  
Wind Source ◽  
X Ray Binaries

AbstractIt is assumed that the acceleration and collimation mechanisms of jets are the same in all the classes of astrophysical objects which are observed to produce jets. These classes now include: active galactic nuclei, young stellar objects, massive x-ray binaries, low mass x-ray binaries, black hole x-ray transients, symbiotic systems, planetary nebulae, and supersoft x-ray sources.On the basis of this assumption, an attempt is made, to identify the necessary ingredients for the acceleration and collimation mechanism. It is argued that: (i) jets are produced at the center of accretion disks which are threaded by a vertical magnetic field, (ii) the production of powerful jets requires, in addition, an energy/wind source associated with the central object. Tentative explanations for the presence of jets in some classes of objects and absence in others are given. Some critical observation that can test the ideas presented in this paper are suggested.

scholarly journals Accretion-induced variability links young stellar objects, white dwarfs, and black holes

2015 ◽  
Vol 1 (9) ◽  
pp. e1500686 ◽  
Author(s):  
Simone Scaringi ◽  
Thomas J. Maccarone ◽  
Elmar Körding ◽  
Christian Knigge ◽  
Simon Vaughan ◽  
...  
Keyword(s):  
Black Holes ◽  
Active Galactic Nuclei ◽  
White Dwarfs ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Young Stellar Objects ◽  
Scaling Relation ◽  
Forming Process ◽  
Stellar Objects

The central engines of disc-accreting stellar-mass black holes appear to be scaled down versions of the supermassive black holes that power active galactic nuclei. However, if the physics of accretion is universal, it should also be possible to extend this scaling to other types of accreting systems, irrespective of accretor mass, size, or type. We examine new observations, obtained withKepler/K2and ULTRACAM, regarding accreting white dwarfs and young stellar objects. Every object in the sample displays the same linear correlation between the brightness of the source and its amplitude of variability (rms-flux relation) and obeys the same quantitative scaling relation as stellar-mass black holes and active galactic nuclei. We also show that the most important parameter in this scaling relation is the physical size of the accreting object. This establishes the universality of accretion physics from proto-stars still in the star-forming process to the supermassive black holes at the centers of galaxies.

scholarly journals On the role of magnetic reconnection in jet/accretion disk systems

2009 ◽  
Vol 5 (H15) ◽  
pp. 247-248 ◽  
Author(s):  
Elisabete M. de Gouveia Dal Pino ◽  
Pamela Piovezan ◽  
Luis Kadowaki ◽  
Grzegorz Kowal ◽  
Alex Lazarian
Keyword(s):  
Active Galactic Nuclei ◽  
Magnetic Reconnection ◽  
Accretion Disk ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Astrophysical Jet ◽  
Radio Flare

AbstractThe most accepted model for jet production is based on the magneto-centrifugal acceleration out off an accretion disk that surrounds the central source (Blandford & Payne, 1982). This scenario, however, does not explain, e.g., the quasi-periodic ejection phenomena often observed in different astrophysical jet classes. de Gouveia Dal Pino & Lazarian (2005) (hereafter GDPL) have proposed that the large scale superluminal ejections observed in microquasars during radio flare events could be produced by violent magnetic reconnection (MR) episodes. Here, we extend this model to other accretion disk systems, namely: active galactic nuclei (AGNs) and young stellar objects (YSOs), and also discuss its hole on jet heating and particle acceleration.

scholarly journals Theory of bipolar flows and jets from young stars

1987 ◽  
Vol 122 ◽  
pp. 51-59
Author(s):  
Colin A. Norman
Keyword(s):  
Galactic Nuclei ◽  
Young Stellar Objects ◽  
Future Research ◽  
Stellar Objects ◽  
Driving Mechanisms ◽  
Stellar Jets ◽  
Current Thinking ◽  
Magnetohydrodynamic Flows ◽  
General Constraints ◽  
Maser Sources

Current thinking on the origin, evolution and stability of stellar jets and bipolar flows is reviewed. Particular emphasis is given to the driving mechanisms of bipolar molecular and ionised gas outflows from young stellar objects. General constraints on both hydrodynamic and magnetohydrodynamic flows are presented. The interrelationship between the protostellar outflows and others such as those associated with powerful, highly collimated outflows in active galactic nuclei are discussed. Intimately connected phenomena such as maser sources and Herbig-Haro objects are briefly treated and finally, areas of potentially interesting future research are indicated.

First Near-infrared Imaging Polarimetry of Young Stellar Objects in the Circinus Molecular Cloud

2018 ◽  
Vol 234 (2) ◽  
pp. 42 ◽  
Author(s):  
Jungmi Kwon ◽  
Takao Nakagawa ◽  
Motohide Tamura ◽  
James H. Hough ◽  
Minho Choi ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Young Stellar Objects ◽  
Near Infrared Imaging ◽  
Stellar Objects ◽  
Imaging Polarimetry
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