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https://phys.org/news/2017-12-cosmic-filament-probes-galaxy-giant.html

Cosmic filament probes our galaxy's giant black hole

December 20, 2017, Harvard-Smithsonian Center for Astrophysics

A radio image from the NSF’s Karl G. Jansky Very Large Array showing the center of our galaxy. The mysterious radio filament is the curved line located near the center of the image, & the supermassive black hole Sagittarius A* (Sgr A*), is shown by the bright source near the bottom of the image. Credit: NSF/VLA/UCLA/M. Morris et al.

The center of our Galaxy has been intensely studied for many years, but it still harbors surprises for scientists. A snake-like structure lurking near our galaxy's supermassive black hole is the latest discovery to tantalize astronomers.

In 2016, Farhad Yusef-Zadeh of Northwestern University reported the discovery of an unusual filament near the center of the Milky Way Galaxy using the NSF's Karl G. Jansky Very Large Array (VLA). The filament is about 2.3 light years long and curves around to point at the supermassive black hole, called Sagittarius A* (Sgr A*), located in the Galactic center.

Now, another team of astronomers has employed a pioneering technique to produce the highest-quality image yet obtained of this curved object.



Read more at: https://phys.org/news/2017-12-cosmic-filament-probes-galaxy-giant.html#jCp

 

the paper:

http://iopscience.iop.org/article/10.3847/2041-8213/aa9985/meta

A Nonthermal Radio Filament Connected to the Galactic Black Hole?

 

Abstract

Using the Very Large Array, we have investigated a nonthermal radio filament (NTF) recently found very near the Galactic black hole and its radio counterpart, Sgr A*. While this NTF—the Sgr A West Filament (SgrAWF)—shares many characteristics with the population of NTFs occupying the central few hundred parsecs of the Galaxy, the SgrAWF has the distinction of having an orientation and sky location that suggest an intimate physical connection to Sgr A*. We present 3.3 and 5.5 cm images constructed using an innovative methodology that yields a very high dynamic range, providing an unprecedentedly clear picture of the SgrAWF. While the physical association of the SgrAWF with Sgr A* is not unambiguous, the images decidedly evoke this interesting possibility. Assuming that the SgrAWF bears a physical relationship to Sgr A*, we examine the potential implications. One is that Sgr A* is a source of relativistic particles constrained to diffuse along ordered local field lines. The relativistic particles could also be fed into the local field by a collimated outflow from Sgr A*, perhaps driven by the Poynting flux accompanying the black hole spin in the presence of a magnetic field threading the event horizon. Second, we consider the possibility that the SgrAWF is the manifestation of a low-mass-density cosmic string that has become anchored to the black hole. The simplest form of these hypotheses would predict that the filament be bi-directional, whereas the SgrAWF is only seen on one side of Sgr A*, perhaps because of the dynamics of the local medium.

 

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