Turbulent Origin of the Galactic Center Magnetic Field: Nonthermal Radio Filaments

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.

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The Compact Nonthermal Radio Source at the Galactic Center: An Update

The Center of the Galaxy ◽

10.1007/978-94-009-2362-1_76 ◽

1989 ◽

pp. 527-534 ◽

Cited By ~ 13

Author(s):

K. Y. Lo

Keyword(s):

Radio Source ◽

Galactic Center ◽

Nonthermal Radio

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Galactic Center threads as nuclear magnetohydrodynamic waves

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa011 ◽

2020 ◽

Vol 72 (2) ◽

Author(s):

Yoshiaki Sofue

Keyword(s):

Magnetic Field ◽

Supernova Remnants ◽

Galactic Center ◽

Mhd Waves ◽

Fast Mode ◽

Magnetohydrodynamic Waves ◽

Compression Waves ◽

Sgr A ◽

The Waves ◽

The Magnetic Field

Abstract Propagation of fast-mode magnetohydrodynamic (MHD) compression waves is traced in the Galactic Center with a poloidal magnetic cylinder. MHD waves ejected from the nucleus are reflected and guided along the magnetic field, exhibiting vertically stretched fronts. The radio threads and non-thermal filaments are explained as due to tangential views of the waves driven by sporadic activity in Sgr A$^*$, or by multiple supernovae. In the latter case, the threads could be extremely deformed relics of old supernova remnants exploded in the nucleus.

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MHD Models of Galactic Center Lobes, Shells, and Filaments

Symposium - International Astronomical Union ◽

10.1017/s0074180900190564 ◽

1990 ◽

Vol 140 ◽

pp. 379-380

Author(s):

Kazunari Shibata ◽

Ryoji Matsumoto

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Galactic Center ◽

Transient State ◽

Rotating Disk ◽

Quasi Equilibrium ◽

Two Dimensional ◽

The Galaxy ◽

Field Lines

Magnetohydrodynamic (MHD) mechanisms producing radio lobes, shells, and filaments in the Galactic center as well as in the gas disk of the Galaxy are studied by using two-dimensional MHD code: (a) the explosion in a magnetized disk, (b) the interaction of a rotating disk with vertical fields, and (c) the nonlinear Parker instability in toroidal magnetic fields in a disk. In all cases, dense shells or filaments are created along magnetic field lines in a transient state, in contrast to the quasi-equilibrium filaments perpendicular to magnetic fields.

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The Nature of the Galactic Center Arc

Symposium - International Astronomical Union ◽

10.1017/s0074180900229768 ◽

1996 ◽

Vol 169 ◽

pp. 263-269 ◽

Cited By ~ 1

Author(s):

E. Serabyn

Keyword(s):

Magnetic Field ◽

Strong Magnetic Field ◽

Galactic Center ◽

Magnetic Energy ◽

Linear Structure ◽

High Energy ◽

Molecular Gas ◽

Synchrotron Emission ◽

Interferometric Imaging ◽

Relativistic Particles

Ever since the Galactic Center Arc was resolved into its component filaments a decade ago, it has been clear that its linear structure arises from the influence of a strong magnetic field. However, the origin and nature of the contributory phenomena have remained elusive. Since what is seen is synchrotron emission from relativistic particles, of prime interest is a knowledge of the acceleration mechanism involved. Interferometric imaging of the molecular gas in the vicinity of the Arc has now provided a tantalizing clue to the Arc's origin: molecular clumps coinciding with the endpoints of a number of the Arc's filaments point to these clumps as the source of the relativistic particles. This suggests that as dense molecular clumps course through the ambient magnetic field at the Galactic Center, magnetic energy is liberated in their leading layers via field reconnection, precipitating rapid acceleration of free charges to high energy.

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Near-infrared Polarimetry and Interstellar Magnetic Fields in the Galactic Center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314011569 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 387-387

Author(s):

S. Nishiyama ◽

H. Hatano ◽

T. Nagata ◽

M. Tamura

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Near Infrared ◽

Galactic Center ◽

Smooth Transition ◽

The Magnetic Field

AbstractWe present a large-scale view of the magnetic field (MF) in the central 3° × 2° region of our Galaxy. There is a smooth transition of the large-scale MF configuration in this region.

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The geometry of the magnetic field in the central molecular zone measured by PILOT

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935072 ◽

2019 ◽

Vol 630 ◽

pp. A74 ◽

Cited By ~ 7

Author(s):

A. Mangilli ◽

J. Aumont ◽

J.-Ph. Bernard ◽

A. Buzzelli ◽

G. de Gasperis ◽

...

Keyword(s):

Magnetic Field ◽

Molecular Clouds ◽

Angular Resolution ◽

Galactic Center ◽

Galactic Plane ◽

Mean Field ◽

Field Orientation ◽

Center Region ◽

The Mean ◽

The Magnetic Field

We present the first far infrared (FIR) dust emission polarization map covering the full extent of Milky Way’s central molecular zone (CMZ). The data, obtained with the PILOT balloon-borne experiment, covers the Galactic center region − 2° < ℓ < 2°, − 4° < b < 3° at a wavelength of 240 μm and an angular resolution of 2.2′. From our measured dust polarization angles, we infer a magnetic field orientation projected onto the plane of the sky (POS) that is remarkably ordered over the full extent of the CMZ, with an average tilt angle of ≃22° clockwise with respect to the Galactic plane. Our results confirm previous claims that the field traced by dust polarized emission is oriented nearly orthogonally to the field traced by GHz radio synchrotron emission in the Galactic center region. The observed field structure is globally compatible with the latest Planck polarization data at 353 and 217 GHz. Upon subtraction of the extended emission in our data, the mean field orientation that we obtain shows good agreement with the mean field orientation measured at higher angular resolution by the JCMT within the 20 and 50 km s−1 molecular clouds. We find no evidence that the magnetic field orientation is related to the 100 pc twisted ring structure within the CMZ. The low polarization fraction in the Galactic center region measured with Planck at 353 GHz combined with a highly ordered projected field orientation is unusual. This feature actually extends to the whole inner Galactic plane. We propose that it could be caused by the increased number of turbulent cells for the long lines of sight towards the inner Galactic plane or to dust properties specific to the inner regions of the Galaxy. Assuming equipartition between magnetic pressure and ram pressure, we obtain magnetic field strength estimates of the order of 1 mG for several CMZ molecular clouds.

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What are the Radio Filaments Near the Galactic Center?

Symposium - International Astronomical Union ◽

10.1017/s0074180900229756 ◽

1996 ◽

Vol 169 ◽

pp. 247-261 ◽

Cited By ~ 1

Author(s):

Mark Morris

Keyword(s):

Magnetic Field ◽

Galactic Center ◽

Galactic Plane ◽

Local Source ◽

Flux Tubes ◽

Flux Lines ◽

Magnetic Flux Tubes ◽

The Magnetic Field ◽

Relativistic Particles ◽

Projected Distance

A population of nonthermally-emitting radio filaments tens of parsecs in length has been observed within a projected distance of ∼130 pc of the Galactic center. More or less perpendicular to the Galactic plane, they appear to define the flux lines of a milligauss magnetic field. The characteristics of the known filaments are summarized. Three fundamental questions raised by these structures are discussed: 1) Do they represent magnetic flux tubes embedded within an ubiquitous, dipole magnetic field permeating the inner Galaxy, but which have been illuminated by some local source of relativistic particles, or are they instead isolated, self-sustaining current paths with an approximately force-free magnetic configuration in pressure equilibrium with the interstellar medium? 2) What is the source of either the magnetic field or the current? and 3) What is the source of the relativistic particles which provide the illuminating synchrotron radiation? We are nearer an answer to the the last of these questions than to the others, although several interesting models have been proposed.

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