scholarly journals Cosmic-ray-driven outflow from the Galactic Centre and the origin of magnetized radio filaments

2019 ◽  
Vol 490 (1) ◽  
pp. L1-L5 ◽  
Author(s):  
F Yusef-Zadeh ◽  
M Wardle
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Galactic Plane ◽  
Formation Rate ◽  
Vertical Direction ◽  
Cosmic Ray ◽  
Molecular Ions ◽  
Galactic Centre ◽  
Azimuthal Magnetic Field ◽  
X Ray

Abstract Radio, X-ray, and infrared observations of the inner few hundred parsecs of the Galactic Centre have highlighted two characteristics of the interstellar medium. The cosmic-ray ionization rate derived from molecular ions such as H$^+_3$ is at least two to three orders of magnitude higher than in the Galactic disc. The other is bipolar X-ray and radio emission away from the Galactic plane. These features are consistent with a scenario in which high cosmic-ray pressure drives large-scale winds away from the Galactic plane. The interaction of such a wind with stellar wind bubbles may explain the energetic non-thermal radio filaments found throughout the Galactic Centre. Some of the implications of this scenario is the removal of gas driven by outflowing winds, acting as a feedback to reduce the star formation rate in the central molecular zone (CMZ), and the distortion of azimuthal magnetic field lines in the CMZ to vertical direction away from the plane. The combined effects of the wind and the vertical magnetic field can explain why most magnetized filaments run perpendicular to the galactic plane. This proposed picture suggests our Milky Way nucleus has recently experienced starburst or black hole activity, as recent radio and X-ray observations indicate.

scholarly journals CHANG-ES

2019 ◽  
Vol 623 ◽  
pp. A33 ◽  
Author(s):  
Y. Stein ◽  
R.-J. Dettmar ◽  
J. Irwin ◽  
R. Beck ◽  
M. Weżgowiec ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Magnetic Fields ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Cosmic Ray ◽  
Transport Processes ◽  
X Ray ◽  
Radio Data ◽  
The Magnetic Field

Context. The observation of total and linearly polarized synchrotron radiation of spiral galaxies in the radio continuum reveals the distribution and structure of their magnetic fields. By observing these, information about the proposed dynamo processes that preserve the large-scale magnetic fields in spiral galaxies can be gained. Additionally, by analyzing the synchrotron intensity, the transport processes of cosmic rays into the halo of edge-on spiral galaxies can be investigated. Aims. We analyze the magnetic field geometry and the transport processes of the cosmic rays of the edge-on spiral starburst galaxy NGC 4666 from CHANG-ES radio data in two frequencies; 6 GHz (C-band) and 1.5 GHz (L-band). Supplementary X-ray data are used to investigate the hot gas in NGC 4666. Methods. We determine the radio scale heights of total power emission at both frequencies for this galaxy. We show the magnetic field orientations derived from the polarization data. Using rotation measure (RM) synthesis we further study the behavior of the RM values along the disk in C-band to investigate the large-scale magnetic-field pattern. We use the revised equipartition formula to calculate a map of the magnetic field strength. Furthermore, we model the processes of cosmic-ray transport into the halo with the 1D SPINNAKER model. Results. The extended radio halo of NGC 4666 is box-shaped and is probably produced by the previously observed supernova-driven superwind. This is supported by our finding of an advective cosmic-ray transport such as that expected for a galactic wind. The scale-height analysis revealed an asymmetric halo above and below the disk as well as between the two sides of the major axis. A central point source as well as a bubble structure is seen in the radio data for the first time. Our X-ray data show a box-shaped hot halo around NGC 4666 and furthermore confirm the AGN nature of the central source. NGC 4666 has a large-scale X-shaped magnetic field in the halo, as has been observed in other edge-on galaxies. The analysis furthermore revealed that the disk of NGC 4666 shows hints of field reversals along its radius, which is the first detection of this phenomenon in an external galaxy.

scholarly journals Observations of Magnetic Fields in Galaxies

1992 ◽  
Vol 9 ◽  
pp. 81-86
Author(s):  
R. Wielebinski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Building Blocks ◽  
Galactic Centre ◽  
Definitive Evidence ◽  
The Galaxy ◽  
The Universe

AbstractMagnetic fields are present in every corner of the Universe. The Earth, the Sun and most of the planets are known to possess dipolar magnetic fields. In the Galaxy many individual objects like stars, pulsars, bipolar nebulae and supernova remnants are found to have associated magnetic fields. It seems that the rotation plays a significant role in the ability of a cosmic object to develop a magnetic field. The magnetic field of the Galaxy is observed to be oriented along the galactic plane as evidenced by both optical and radio polarization observations. Radio maps of the Galactic centre reveal poloidal magnetic fields as ‘wisps’ or ‘strings’ around Sagittarius A. Observations of nearby galaxies give us remarkable information about the large-scale magnetic fields in these building blocks of the Universe. Magnetic fields play an important role in the formation of jets of radio galaxies. Further out, in clusters of galaxies, definitive evidence has been given for the existence of intergalactic magnetic fields.

AGN torus threaded by large scale magnetic field

2018 ◽  
Vol 27 (10) ◽  
pp. 1844006
Author(s):  
A. Dorodnitsyn ◽  
T. Kallman
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Accretion Disk ◽  
Large Scale ◽  
Three Dimensional ◽  
X Ray ◽  
Radiative Feedback ◽  
Large Scale Magnetic Field ◽  
Three Dimensional Simulations

Large scale magnetic field can be easily dragged from galactic scales toward AGN along with accreting gas. There, it can contribute to both the formation of AGN “torus” and help to remove angular momentum from the gas which fuels AGN accretion disk. However the dynamics of such gas is also strongly influenced by the radiative feedback from the inner accretion disk. Here we present results from the three-dimensional simulations of pc-scale accretion which is exposed to intense X-ray heating.

scholarly journals Radio and X-ray connection in radio mini-halos: Implications for hadronic models

2020 ◽  
Vol 640 ◽  
pp. A37 ◽  
Author(s):  
A. Ignesti ◽  
G. Brunetti ◽  
M. Gitti ◽  
S. Giacintucci
Keyword(s):  
Magnetic Field ◽  
Large Fraction ◽  
Cosmic Ray ◽  
Physical Parameters ◽  
Model Parameters ◽  
Relativistic Electrons ◽  
X Rays ◽  
X Ray ◽  
Hadronic Model ◽  
Radio Halos

Context. A large fraction of cool-core clusters are known to host diffuse, steep-spectrum radio sources, called radio mini-halos, in their cores. Mini-halos reveal the presence of relativistic particles on scales of hundreds of kiloparsecs, beyond the scales directly influenced by the central active galactic nucleus (AGN), but the nature of the mechanism that produces such a population of radio-emitting, relativistic electrons is still debated. It is also unclear to what extent the AGN plays a role in the formation of mini-halos by providing the seeds of the relativistic population. Aims. In this work we explore the connection between thermal and non-thermal components of the intra-cluster medium in a sample of radio mini-halos and we study the implications within the framework of a hadronic model for the origin of the emitting electrons. Methods. For the first time, we studied the thermal and non-thermal connection by carrying out a point-to-point comparison of the radio and the X-ray surface brightness in a sample of radio mini-halos. We extended the method generally applied to giant radio halos by considering the effects of a grid randomly generated through a Monte Carlo chain. Then we used the radio and X-ray correlation to constrain the physical parameters of a hadronic model and we compared the model predictions with current observations. Results. Contrary to what is generally reported in the literature for giant radio halos, we find that the mini-halos in our sample have super-linear scaling between radio and X-rays, which suggests a peaked distribution of relativistic electrons and magnetic field. We explore the consequences of our findings on models of mini-halos. We use the four mini-halos in the sample that have a roundish brightness distribution to constrain model parameters in the case of a hadronic origin of the mini-halos. Specifically, we focus on a model where cosmic rays are injected by the central AGN and they generate secondaries in the intra-cluster medium, and we assume that the role of turbulent re-acceleration is negligible. This simple model allows us to constrain the AGN cosmic ray luminosity in the range ∼1044−46 erg s−1 and the central magnetic field in the range 10–40 μG. The resulting γ-ray fluxes calculated assuming these model parameters do not violate the upper limits on γ-ray diffuse emission set by the Fermi-LAT telescope. Further studies are now required to explore the consistency of these large magnetic fields with Faraday rotation studies and to study the interplay between the secondary electrons and the intra-cluster medium turbulence.

scholarly journals A Multi-Wavelength View of the XMM-Newton Galactic Plane

2014 ◽  
Vol 1 (1) ◽  
pp. 123-126
Author(s):  
Ada Nebot Gómez-Morán ◽  
Christian Motch
Keyword(s):  
Surface Density ◽  
Binary Systems ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Galactic Latitude ◽  
X Ray ◽  
Model Predictions ◽  
Science Centre ◽  
Multi Wavelength ◽  
Galactic Longitude

We present an X-ray survey of the Galactic Plane conducted by the Survey Science Centre of the XMM-Newton satellite. The survey contains more than 1300 X-ray detections at low and intermediate Galactic latitudes and covering 4 deg<sup>2</sup> well spread in Galactic longitude. From a multi-wavelength analysis, using optical spectra and helped by optical and infrared photometry we identify and classify about a fourth of the sources. The observed surface density of soft X-ray (&lt;2 keV) sources decreases with Galactic latitude and although compatible with model predictions at first glance, presents an excess of stars, likely due to giants in binary systems. In the hard band (&gt;2 keV) the surface density of sources presents an excess with respect to the expected extragalactic contribution. This excess highly concentrates towards the direction of the Galactic Centre and is compatible with previous results from Chandra observations around the Galactic Centre. The nature of these sources is still unknown.

scholarly journals Prominence Disappearance Related to CMEs

1998 ◽  
Vol 167 ◽  
pp. 380-383
Author(s):  
E. Hiei
Keyword(s):  
Magnetic Field ◽  
Solar Disk ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
X Ray ◽  
Dynamic Phenomena

AbstractDB (disparition brusque) events are associated with dynamic phenomena such as a CME, a flare, brightening of a soft X-ray arcade, and soft X-ray dimming, and probably a change of the coronal magnetic field on a large scale. The DB event observed on January 16, 1993 identified with a CME occurred on the solar disk.

scholarly journals On the flux of high-energy cosmogenic neutrinos and the influence of the extragalactic magnetic field

2019 ◽  
Vol 488 (1) ◽  
pp. L119-L122 ◽  
Author(s):  
David Wittkowski ◽  
Karl-Heinz Kampert
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Large Scale ◽  
Neutrino Flux ◽  
Cosmic Ray ◽  
High Energy ◽  
Observation Time ◽  
Cosmological Time ◽  
Cosmic Background ◽  
The Universe

ABSTRACT Cosmogenic neutrinos originate from interactions of cosmic rays propagating through the universe with cosmic background photons. Since both high-energy cosmic rays and cosmic background photons exist, the existence of high-energy cosmogenic neutrinos is certain. However, their flux has not been measured so far. Therefore, we calculated the flux of high-energy cosmogenic neutrinos arriving at the Earth on the basis of elaborate 4D simulations that take into account three spatial degrees of freedom and the cosmological time-evolution of the universe. Our predictions for this neutrino flux are consistent with the recent upper limits obtained from large-scale cosmic-ray experiments. We also show that the extragalactic magnetic field has a strong influence on the neutrino flux. The results of this work are important for the design of future neutrino observatories, since they allow to assess the detector volume and observation time that are necessary to detect high-energy cosmogenic neutrinos in the near future. An observation of such neutrinos would push multimessenger astronomy to hitherto unachieved energy scales.

scholarly journals Chandra COSMOS Legacy Survey: Clustering dependence of Type 2 active galactic nuclei on host galaxy properties

2019 ◽  
Vol 632 ◽  
pp. A88
Author(s):  
V. Allevato ◽  
A. Viitanen ◽  
A. Finoguenov ◽  
F. Civano ◽  
H. Suh ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Scale ◽  
Formation Rate ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Host Galaxy ◽  
X Ray ◽  
Normal Galaxies ◽  
Massive Halos

Aims. We perform clustering measurements of 800 X-ray selected Chandra COSMOS Legacy (CCL) Type 2 active galactic nuclei (AGN) with known spectroscopic redshift to probe the halo mass dependence on AGN host galaxy properties, such as galaxy stellar mass Mstar, star formation rate (SFR), and specific black hole accretion rate (BHAR; λBHAR) in the redshift range z = [0−3]. Methods. We split the sample of AGN with known spectroscopic redshits according to Mstar, SFR and λBHAR, while matching the distributions in terms of the other parameters, including redshift. We measured the projected two-point correlation function wp(rp) and modeled the clustering signal, for the different subsamples, with the two-halo term to derive the large-scale bias b and corresponding typical mass of the hosting halo. Results. We find no significant dependence of the large-scale bias and typical halo mass on galaxy stellar mass and specific BHAR for CCL Type 2 AGN at mean z ∼ 1, while a negative dependence on SFR is observed, i.e. lower SFR AGN reside in richer environment. Mock catalogs of AGN, matched to have the same X-ray luminosity, stellar mass, λBHAR, and SFR of CCL Type 2 AGN, almost reproduce the observed Mstar − Mh, λBHAR − Mh and SFR–Mh relations, when assuming a fraction of satellite AGN fAGNsat ∼ 0.15. This corresponds to a ratio of the probabilities of satellite to central AGN of being active Q ∼ 2. Mock matched normal galaxies follow a slightly steeper Mstar − Mh relation, in which low mass mock galaxies reside in less massive halos than mock AGN of similar mass. Moreover, matched mock normal galaxies are less biased than mock AGN with similar specific BHAR and SFR, at least for Q >  1.

scholarly journals Probing interstellar magnetic fields with Supernova remnants

2008 ◽  
Vol 4 (S259) ◽  
pp. 75-80 ◽  
Author(s):  
Roland Kothes ◽  
Jo-Anne Brown
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Field Configuration ◽  
Large Scale Magnetic Field ◽  
Rotation Measure ◽  
Field Lines ◽  
The Magnetic Field

AbstractAs Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.

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