CHANG-ES: XVIII—The CHANG-ES Survey and Selected Results

The CHANG-ES (Continuum Halos in Nearby Galaxies) survey of 35 nearby edge-on galaxies is revealing new and sometimes unexpected and startling results in their radio continuum emission. The observations were in wide bandwidths centred at 1.6 and 6.0 GHz. Unique to this survey is full polarization data showing magnetic field structures in unprecedented detail, resolution and sensitivity for such a large sample. A wide range of new results are reported here, some never before seen in any galaxy. We see circular polarization and variability in active galactic nuclei (AGNs), in-disk discrete features, disk-halo structures sometimes only seen in polarization, and broad-scale halos with reversing magnetic fields, among others. This paper summarizes some of the CHANG-ES results seen thus far.

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The resolved radio–FIR correlation in nearby galaxies with Herschel and Spitzer

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312009507 ◽

2011 ◽

Vol 7 (S284) ◽

pp. 400-403

Author(s):

Fatemeh S. Tabatabaei ◽

Eva Schinnerer ◽

Eric Murphy ◽

Rainer Beck ◽

Annie Hughes ◽

...

Keyword(s):

Magnetic Field ◽

Diffusion Length ◽

Spatial Scales ◽

Cosmic Ray ◽

Far Infrared ◽

Scale Dependence ◽

Radio Continuum ◽

Continuum Emission ◽

Synchrotron Emission ◽

Nearby Galaxies

AbstractWe investigate the correlation between the far-infrared (FIR) and radio continuum emission from NGC6946 on spatial scales between 0.9 and 17 kpc. We use the Herschel PACS (70, 100, 160μm) and SPIRE (250μm) data from the KINGFISH project. Separating the free-free and synchrotron components of the radio continuum emission, we find that FIR is better correlated with the free-free than the synchrotron emission. Compared to a similar study in M33 and M31, we find that the scale dependence of the synchrotron–FIR correlation in NGC6946 is more similar to M31 than M33. The scale dependence of the synchrotron–FIR correlation can be explained by the turbulent-to-ordered magnetic field ratio or, equivalently, the diffusion length of the cosmic ray electrons in these galaxies.

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VLBA Imaging of a Large Sample of Blazars

International Astronomical Union Colloquium ◽

10.1017/s0252921100044997 ◽

1998 ◽

Vol 164 ◽

pp. 159-160

Author(s):

J. M. Attridge ◽

D. H. Roberts ◽

J. F.C. Wardle

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Active Galactic Nuclei ◽

Ambient Medium ◽

Surrounding Medium ◽

Galactic Nuclei ◽

Large Sample ◽

Field Lines ◽

5 Ghz ◽

The Magnetic Field

AbstractAs part of our continuing study of parsec-scale magnetic fields in active galactic nuclei we have obtained deep polarization-sensitive images of the blazar 1055+018 with the VLBA at 5 GHz. These dramatic images reveal a magnetized layer of material on the outer surfaces of the jet, distinct from the bulk of the jet. This morphology suggests interaction of the jet with the surrounding medium, the resulting shear stretching the magnetic field lines in the direction of the flow. Further multi-frequency polarization-sensitive observations of 1055+018 offer the opportunity to study radio jet-ambient medium interactions in detail.

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Cosmic evolution of AGN with moderate-to-high radiative luminosity in the COSMOS field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000030 ◽

2017 ◽

Vol 12 (S333) ◽

pp. 195-198

Author(s):

L. Ceraj ◽

V. Smolčić ◽

I. Delvecchio ◽

J. Delhaize ◽

M. Novak

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Radio Continuum ◽

Continuum Emission ◽

Number Density ◽

X Ray ◽

Cosmic Evolution ◽

Luminosity Functions ◽

Multi Wavelength ◽

First Time

AbstractWe study the moderate-to-high radiative luminosity active galactic nuclei (HLAGN) within the VLA-COSMOS 3 GHz Large Project. The survey covers 2.6 square degrees centered on the COSMOS field with a 1σ sensitivity of 2.3 μJy/beam across the field. This provides the simultaneously largest and deepest radio continuum survey available to date with exquisite multi-wavelength coverage. The survey yields 10,830 radio sources with signal-to-noise ratios ≥5. A subsample of 1,604 HLAGN is analyzed here. These were selected via a combination of X-ray luminosity and mid-infrared colors. We derive luminosity functions for these AGN and constrain their cosmic evolution out to a redshift of z ∼ 6, for the first time decomposing the star formation and AGN contributions to the radio continuum emission in the AGN. We study the evolution of number density and luminosity density finding a peak at z ∼ 1.5 followed by a decrease out to a redshift z ∼ 6.

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Discovery of Helical Magnetic Fields in AGN, and CME and Ejection of Large-Scale Magnetic Fields from AGN

Symposium - International Astronomical Union ◽

10.1017/s007418090019463x ◽

2003 ◽

Vol 214 ◽

pp. 303-308

Author(s):

Han-Shu Chu ◽

L. B. Baath ◽

Fu-Jun Zhang ◽

R. E. Spencer

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Active Galactic Nuclei ◽

Large Scale ◽

Direct Detection ◽

Galactic Nuclei ◽

Crucial Importance ◽

Important Ingredient ◽

Celestial Bodies ◽

Helical Magnetic Field

Magnetic Fields are the crucial and most important ingredient involved in the processes of various violent activities in Active Galactic Nuclei and other celestial bodies. The generally accepted 2-sided symmetric-jets model of active galactic nuclei (AGN) does not include the magnetic fields. We present here the first direct detection of helical magnetic field in AGN, and the first direct detection of ejection of large scale magnetic fields from AGN. (CME) 2. The annular (helical) magnetic field is responsible for the collimation of the jet (through Pinch Effect) and may be of crucial importance for extraction of black hole rotational energy. 3. The CMEs are responsible for sporadic ejection of jet components in AGN, while the general accepted 2-sided jets pertain to the quiescent Jets. 4. Observations show that the CME with Asymmetric Jets can explain many phenomena and much of the morphological diversities in AGN.

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Radio continuum emission of the Milky Way and nearby galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900242538 ◽

1985 ◽

Vol 106 ◽

pp. 239-244 ◽

Cited By ~ 1

Author(s):

Rainer Beck ◽

Wolfgang Reich

Keyword(s):

Magnetic Field ◽

Central Region ◽

Milky Way ◽

Thin Disk ◽

Radio Continuum ◽

Continuum Emission ◽

Spiral Arms ◽

Ordered Field ◽

Nearby Galaxies ◽

The Magnetic Field

The radio continuum emission of the Milky Way and nearby galaxies can be decomposed into a central region, a clumpy “thin disk”, concentrated in the spiral arms, and a smooth “thick disk” (or flattened “halo”). The emissivity ratio of the two disks seems to be related to the magnetic field properties: Galaxies with strong radio spiral arms reveal a highly ordered field following the arm direction, while galaxies with diffuse disks contain a less ordered, smoothly distributed field. The degree of uniformity of the field seems to correlate with the total optical luminosity. The average magnetic field in the Milky Way is weak and turbulent compared to most of the nearby galaxies observed so far.

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A Search for Low-Level Seyfert Activity in the 500 Brightest Northern Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900155470 ◽

1987 ◽

Vol 121 ◽

pp. 451-460

Author(s):

Alexei V. Filippenko ◽

Wallace L. W. Sargent

Keyword(s):

Active Galactic Nuclei ◽

Luminosity Function ◽

Galactic Nuclei ◽

Emission Lines ◽

Full Width ◽

Line Region ◽

Wide Range ◽

Hα Emission ◽

Nearby Galaxies ◽

Narrow Line Region

A sensitive search for intrinsically faint Seyfert nuclei in the 500 brightest northern galaxies is being conducted with the Hale 5.08 m telescope. The primary aim is to extend the luminosity function of active galactic nuclei (AGNs) to lower luminosities. Thus far, we have detected Hα emission having full-width near zero-intensity (FWZI) ≳ 4000 km s−1 in a significant fraction (≳10%) of nearby galaxies. Moreover, the narrow emission lines in a given nucleus often have markedly different widths, as shown in detail for M81. Those associated with high critical densities are generally the broadest, indicating that a very wide range of densities is present in the narrow-line region. The relative intensities of the lines can readily be explained with models in which clouds of gas having ne ≈ 102 to 107 cm−3 are photoionized by nonstellar radiation such as that produced by QSOs and luminous Seyfert 1 galaxies.

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No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽

10.3390/data6010004 ◽

2021 ◽

Vol 6 (1) ◽

pp. 4

Author(s):

Evgeny Mikhailov ◽

Daniela Boneva ◽

Maria Pashentseva

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Point Of View ◽

Accretion Discs ◽

Wide Range ◽

Astrophysical Objects ◽

Alpha Effect ◽

The Stability ◽

The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

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Understanding the origin of radio outflows in Seyfert galaxies using radio polarimetry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003014 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 247-251

Author(s):

Biny Sebastian ◽

Preeti Kharb ◽

Christopher P. O’ Dea ◽

Jack F. Gallimore ◽

Stefi A. Baum ◽

...

Keyword(s):

Magnetic Fields ◽

Radio Emission ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxy ◽

Seyfert Galaxies ◽

Starburst Galaxies ◽

Galactic Magnetic Fields ◽

5 Ghz

AbstractThe role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

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