scholarly journals Magnetic Fields & Ionized Gas in Elliptical Galaxy Halos

1990 ◽  
Vol 140 ◽  
pp. 459-462
Author(s):  
Richard G. Strom
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Elliptical Galaxy ◽  
Radio Sources ◽  
Early Type ◽  
Ionized Gas ◽  
X Ray ◽  
Galaxy Halos ◽  
Field Strengths

Faraday depolarization estimates of thermal densities within the components of double radio sources agree well with estimates from X-ray observations of hot halos around early-type galaxies, provided magnetic field strengths are close to their equipartition values. Internal Faraday dispersion is the main cause of the depolarization observed.

scholarly journals An X‐Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources

2005 ◽  
Vol 626 (2) ◽  
pp. 733-747 ◽  
Author(s):  
J. H. Croston ◽  
M. J. Hardcastle ◽  
D. E. Harris ◽  
E. Belsole ◽  
M. Birkinshaw ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Sources ◽  
Particle Content ◽  
X Ray ◽  
Field Strengths

scholarly journals Feedback and environmental effects in elliptical galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 289-290
Author(s):  
Craig L. Sarazin
Keyword(s):  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Energy Output ◽  
Radio Sources ◽  
Early Type ◽  
Gas Stripping ◽  
Interstellar Gas ◽  
X Ray ◽  
Radio Jets

AbstractThe role of the environment of an elliptical galaxy on its hot interstellar gas is discussed. In general, the X-ray halos of early-type galaxies tend to be smaller and fainter in denser environments, with the exception of group-central galaxies. X-ray observations show many examples of nearby galaxies which are undergoing gas stripping. On the other hand, most bright galaxies in clusters do manage to retain small coronae of X-ray emission. Recent theoretical and observational results on the role of feedback from AGN at the centers of elliptical galaxies on their interstellar gas are reviewed. X-ray observations show many examples of X-ray holes in the central regions of brightest-cluster galaxies; in many cases, the X-ray holes are filled with radio lobes. Similar radio bubbles are seen in groups and individual early-type galaxies. “Ghost bubbles” are often seen at larger radii in clusters and galaxies; these bubbles are faint in high radio frequencies, and are believed to be old radio bubbles which have risen buoyantly in the hot gas. Low frequency radio observations show that many of the ghost bubbles have radio emission; in general, these long wavelength observations show that radio sources are much larger and involve greater energies than had been previously thought. The radio bubbles can be used to estimate the total energy output of the radio jets. The total energies deposited by radio jets exceed the losses from the gas due to radiative cooling, indicating that radio sources are energetically capable of heating the cooling core gas and preventing rapid cooling.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

scholarly journals Modeling of magneto-conductivity of bismuth selenide: a topological insulator

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Yogesh Kumar ◽  
Rabia Sultana ◽  
Prince Sharma ◽  
V. P. S. Awana
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Single Crystal ◽  
Single Crystals ◽  
X Ray Diffraction ◽  
Field Range ◽  
X Ray ◽  
Bulk Carriers ◽  
Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

Supermassive Black Hole feedback in early type galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 119-125
Author(s):  
W. Forman ◽  
C. Jones ◽  
A. Bogdan ◽  
R. Kraft ◽  
E. Churazov ◽  
...  
Keyword(s):  
Dark Matter Halo ◽  
Scaling Relations ◽  
Radio Sources ◽  
Early Type ◽  
X Ray ◽  
Galaxy Groups ◽  
Sufficient Energy ◽  
The Galaxy ◽  
Simple Scaling ◽  
Halo Masses

AbstractOptically luminous early type galaxies host X-ray luminous, hot atmospheres. These hot atmospheres, which we refer to as coronae, undergo the same cooling and feedback processes as are commonly found in their more massive cousins, the gas rich atmospheres of galaxy groups and galaxy clusters. In particular, the hot coronae around galaxies radiatively cool and show cavities in X-ray images that are filled with relativistic plasma originating from jets powered by supermassive black holes (SMBH) at the galaxy centers. We discuss the SMBH feedback using an X-ray survey of early type galaxies carried out using Chandra X-ray Observatory observations. Early type galaxies with coronae very commonly have weak X-ray active nuclei and have associated radio sources. Based on the enthalpy of observed cavities in the coronae, there is sufficient energy to “balance” the observed radiative cooling. There are a very few remarkable examples of optically faint galaxies that are 1) unusually X-ray luminous, 2) have large dark matter halo masses, and 3) have large SMBHs (e.g., NGC4342 and NGC4291). These properties suggest that, in some galaxies, star formation may have been truncated at early times, breaking the simple scaling relations.

scholarly journals Investigating the Magnetospheres of Rapidly Rotating B-type Stars

2016 ◽  
Vol 12 (S329) ◽  
pp. 369-372
Author(s):  
C. L. Fletcher ◽  
V. Petit ◽  
Y. Nazé ◽  
G. A. Wade ◽  
R. H. Townsend ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Centrifugal Force ◽  
Point Of View ◽  
Closed Field ◽  
Theoretical Point ◽  
X Rays ◽  
Rapid Rotation ◽  
X Ray ◽  
Surface Magnetic Field

AbstractRecent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars.

scholarly journals Magnetic Field Strengths of GPS Radio Sources

1999 ◽  
Vol 194 ◽  
pp. 324-326
Author(s):  
V. G. Panajyan
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Radio Sources ◽  
Spectral Indices ◽  
The Past ◽  
Spectrum Radio ◽  
Field Strengths

GHz peaked spectrum radio sources (GPS) are believed to be a subclass of compact steep spectrum radio sources (CSS) with high frequency spectral indices α < −0.5 (5 ˜ vα), linear sizes of pc to kpc scale and turnover spectra near 1GHz. Due to the work of many radioastronomers during the past two decades many properties of CSS and GPS radio sources at present are known (O'Dea,C.P. et al.1998, and references therein).

scholarly journals Extragalactic megahertz-peaked spectrum radio sources at milliarcsecond scales

2019 ◽  
Vol 628 ◽  
pp. A56 ◽  
Author(s):  
M. A. Keim ◽  
J. R. Callingham ◽  
H. J. A. Röttgering
Keyword(s):  
Magnetic Field ◽  
Spectral Characteristics ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Long Baseline ◽  
Spectrum Radio ◽  
Spectral Peaks ◽  
Murchison Widefield Array ◽  
Very Long Baseline Array ◽  
Field Strengths

Extragalactic peaked-spectrum radio sources are thought to be the progenitors of larger, radio-loud active galactic nuclei (AGN). Synchrotron self-absorption (SSA) has often been identified as the cause of their spectral peak. The identification of new megahertz-peaked spectrum sources from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey provides an opportunity to test how radio sources with spectral peaks below 1 GHz fit within this evolutionary picture. We observed six peaked-spectrum sources selected from the GLEAM survey, three that have spectral characteristics which violate SSA and three that have spectral peaks below 230 MHz, with the Very Long Baseline Array at 1.55 and 4.96 GHz. We present milliarcsecond resolution images of each source and constrain their morphology, linear size, luminosity, and magnetic field strength. Of the sources that are resolved by our study, the sources that violate SSA appear to be compact doubles, while the sources with peak frequencies below 230 MHz have core-jet features. We find that all of our sources are smaller than expected from SSA by factors of ≳20. We also find that component magnetic field strengths calculated from SSA are likely inaccurate, differing by factors of ≳5 from equipartition estimates. The calculated equipartition magnetic field strengths more closely resemble estimates from previously studied gigahertz-peaked spectrum sources. Exploring a model of the interaction between jets and the interstellar medium, we demonstrate that free-free absorption (FFA) can accurately describe the linear sizes and peak frequencies of our sources. Our findings support the theory that there is a fraction of peaked-spectrum sources whose spectral peaks are best modeled by FFA, implying our understanding of the early stages of radio AGN is incomplete.

scholarly journals Cyclotron lines in highly magnetized neutron stars

2019 ◽  
Vol 622 ◽  
pp. A61 ◽  
Author(s):  
R. Staubert ◽  
J. Trümper ◽  
E. Kendziorra ◽  
D. Klochkov ◽  
K. Postnov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Direct Measurement ◽  
Resonant Scattering ◽  
Electron Cyclotron ◽  
X Ray ◽  
Cyclotron Line ◽  
The Magnetic Field ◽  
Proton Cyclotron

Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (end 2018), we list 35 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

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