The Galactic centre mini-spiral in the mm-regime

Kunneriath, D.; Eckart, A.; Vogel, S. N.; Teuben, Peter; Mužić, K.; Schödel, R.; García-Marín, M.; Moultaka, J.; Staguhn, Johannes; Straubmeier, C.; Zensus, J. A.; Valencia-S., M.; Karas, V.

doi:10.1051/0004-6361/201117676

Cited by 31 publications

(30 citation statements)

References 34 publications

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“…The evidence is more complicated in the case of our Galactic Center (despite its relative proximity) because there is no standard accretion disc present [3]. However, we can still clearly resolve the inflowing material and numerous effects of the past activity [10,18], which also prove the relevance of the threecomponent scenario. The three mentioned subsystems are in mutual interaction with each other, and the role of this interaction is essential for their long-term behaviour.…”

Section: Introductionmentioning

confidence: 80%

Enhancing the rate of tidal disruptions of stars by a self-gravitating disc around a massive central black hole

Karas

Šubr

2012

EPJ Web of Conferences

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Abstract. We further study the idea that a self-gravitating accretion disc around a supermassive black hole can increase the rate of gradual orbital decay of stellar trajectories (and hence tidal disruption events) by setting some stars on eccentric trajectories. Cooperation between the gravitational field of the disc and the dissipative environment can provide a mechanism explaining the origin of stars that become bound tightly to the central black hole. We examine this process as a function of the black hole mass and conclude that it is most efficient for intermediate central masses of the order of ∼10 4 M . Members of the cluster experience the stage of orbital decay via collisions with an accretion disc and by other dissipative processes, such as tidal effects, dynamical friction and the emission of gravitational waves. Our attention is concentrated on the region of gravitational dominance of the central body. Mutual interaction between stars and the surrounding environment establishes a non-spherical shape and anisotropy of the nuclear cluster. In some cases, the stellar sub-system acquires ring-type geometry. Stars of the nuclear cluster undergo a tidal disruption event as they plunge below the tidal radius of the supermassive black hole.

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Section: Introductionmentioning

confidence: 80%

Enhancing the rate of tidal disruptions of stars by a self-gravitating disc around a massive central black hole

Karas

Šubr

2012

EPJ Web of Conferences

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“…If the line shape of the calculated spectrum of γ-ray emission in the clumpy structure is consistent with the result observed by the HESS experiment, this can further support our model of adopting the VFF. In the central region, the minispiral is a region with a stellar population cluster and density structure, which consists of four main components: the northern arm, the western arc, the eastern arm and the bar (Kunneriath et al 2012). In those streamers, it is very bright in the near-infrared wave band and possible P Pcollision regime.…”

Section: Discussionmentioning

confidence: 99%

The Galactic Center: A Petaelectronvolt Cosmic-ray Acceleration Factory

Guo

Tian

Wang

et al. 2017

ApJ

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The multi-TeV γ-rays from the Galactic Center (GC) have a cutoff at tens of TeV, whereas the diffuse emission has no such cutoff, which is regarded as an indication of PeV proton acceleration by the HESS experiment. It is important to understand the inconsistency and study the possibility that PeV cosmic-ray acceleration could account for the apparently contradictory point and diffuse γ-ray spectra.In this work, we propose that the cosmic rays are accelerated up to >PeV in GC. The interaction between cosmic rays and molecular clouds is responsible for the multi-TeV γ-ray emissions from both the point source and diffuse sources today. Enhanced by the small volume filling factor (VFF) of the clumpy structure, the absorption of the γ-rays leads to a sharp cutoff spectrum at tens of TeV produced in the GC. Away from galactic center, the VFF grows and the absorption enhancement becomes negligible.As a result, the spectra of γ-ray emissions for both point source and diffuse sources can be successfully reproduced under such self-consistent picture. In addition, a "surviving-tail" at ∼100 TeV is expected from the point source, which can be observed by future projects CTA and LHAASO. Neutrinos are simultaneously produced during proton-proton (PP) collision. With 5-10 years observations, the KM3Net experiment will be able to detect the PeV source according to our calculation.

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“…Under such conditions the accreted medium consists of complex plasma with a nonnegligible content of dust (Chan et al 1997). Located at a distance about 0.1-0.2 pc (projected distance ∼0.06 pc) from the supermassive black hole, this feature can be understood as consisting of three independent clumpy streams of mainly gaseous material at roughly Keplerian motion around the centre (Zhao et al 2010;Kunneriath et al 2012). The streams collide, and their mutual interaction may cause the loss of angular momentum and an occasional inflow of the clumpy material towards the black hole (Paumard et al 2005;Czerny et al 2013a).…”

Section: Discussionmentioning

confidence: 99%

Dust-enshrouded star near supermassive black hole: predictions for high-eccentricity passages near low-luminosity galactic nuclei

Karas

Eckart

2014

A&A

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Context. Supermassive black holes reside in cores of galaxies, where they are often surrounded by a nuclear cluster and a clumpy torus of gas and dust. Mutual interactions can set some stars on a plunging trajectory towards the black hole. Aims. We model the pericentre passage of a dust-enshrouded star during which the dusty envelope becomes stretched by tidal forces and is affected by the interaction with the surrounding medium. In particular, we explore under which conditions these encounters can lead to periods of enhanced accretion activity. Methods. We discuss different scenarios for such a dusty source. To this end, we employed a modification of the Swift integration package. Elements of the cloud were modelled as numerical particles that represent the dust component that interacts with the optically thin gaseous environment. Results. We determine the fraction of the total mass of the dust component that is diverted from the original path during the passages through the pericentre at 10 3 Schwarzschild radii and find that the main part of the dust ( 90% of its mass) is significantly affected upon the first crossing. The fraction of mass captured at the second passage generally decreases to very low values. Conclusions. As an example, we show predictions for the dusty source evolution assuming the current orbital parameters of the G2 cloud (also known as Dusty S-Cluster Object, DSO) in our Galactic centre. Encounter of a core-less cloud with a supermassive black hole is, most likely, a non-repeating event: the cloud is destroyed. However, in the case of a dust-enshrouded star, part of the envelope survives the pericentre passage. We discuss an offset of 0.3 arcsec between the centre of mass of the diverted part and the star along the eccentric orbit. Finally, we examine an interesting possibility of a binary star embedded within a common wind envelope that becomes dispersed at the pericentre passage.

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The Galactic centre mini-spiral in the mm-regime

Cited by 31 publications

References 34 publications

Enhancing the rate of tidal disruptions of stars by a self-gravitating disc around a massive central black hole

Enhancing the rate of tidal disruptions of stars by a self-gravitating disc around a massive central black hole

The Galactic Center: A Petaelectronvolt Cosmic-ray Acceleration Factory

Dust-enshrouded star near supermassive black hole: predictions for high-eccentricity passages near low-luminosity galactic nuclei

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