MODELING THE MAGNETIC FIELD IN THE GALACTIC DISK USING NEW ROTATION MEASURE OBSERVATIONS FROM THE VERY LARGE ARRAY

Abstract Radio relics are sites of electron (re)acceleration in merging galaxy clusters but the mechanism of acceleration and the topology of the magnetic field in and near relics are yet to be understood. We are carrying out an observational campaign on double relic galaxy clusters starting with RXC J1314.4-2515. With Jansky Very Large Array multi-configuration observations in the frequency range 1-4 GHz, we perform both spectral and polarization analyses, using the Rotation Measure synthesis technique. We use archival XMM-Newton observations to constrain the properties of the shocked region. We discover a possible connection between the activity of a radio galaxy and the emission of the eastern radio relic. In the northern elongated arc of the western radio relic, we detect polarized emission with an average polarization fraction of 31 % at 3 GHz and we derive the Mach number of the underlying X-ray shock. Our observations reveal low levels of fractional polarization and Faraday-complex structures in the southern region of the relic, which point to the presence of thermal gas and filamentary magnetic field morphology inside the radio emitting volume. We measured largely different Rotation Measure dispersion from the two relics. Finally, we use cosmological magneto-hydrodynamical simulations to constrain the magnetic field, viewing angle, and to derive the acceleration efficiency of the shock. We find that the polarization properties of RXC J1314.4-2515 are consistent with a radio relic observed at 70○ with respect to the line of sight and that efficient re-acceleration of fossil electrons has taken place.

Download Full-text

Magnetic-Field Vector Maps of Nearby Spiral Galaxies

Galaxies ◽

10.3390/galaxies7010032 ◽

2019 ◽

Vol 7 (1) ◽

pp. 32 ◽

Cited By ~ 1

Author(s):

Hiroyuki Nakanishi ◽

Kohei Kurahara ◽

Kenta Anraku

Keyword(s):

Magnetic Field ◽

Spiral Galaxies ◽

Transverse Magnetic ◽

Field Vector ◽

Line Of Sight ◽

Large Array ◽

Magnetic Vector ◽

Very Large Array ◽

Rotation Measure ◽

The Galaxy

We present a method for determining the directions of magnetic-field vectors in a spiral galaxy using two synchrotron polarization maps, an optical image, and a velocity field. The orientation of the transverse magnetic field is determined with a synchrotron polarization map of a higher-frequency band, and the 180 ∘ -ambiguity is solved by using a sign of Rotation Measure (RM) after determining the geometrical orientation of a disk based on an assumption of trailing spiral arms. The advantage of this method is that the direction of a magnetic vector for each line of sight throughout the galaxy can inexpensively be determined, with easily available data and simple assumptions. We applied this method to three nearby spiral galaxies using archival data obtained with a Very Large Array (VLA) to demonstrate how it works. The three galaxies have both clockwise and counterclockwise magnetic fields, which implies that none of the three galaxies is classified in a simple Axis-Symmetric type, but types of higher modes, and that magnetic reversals commonly exist.

Download Full-text

The discovery of secondary lobes in the Seyfert galaxy NGC 2639

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz136 ◽

2019 ◽

Vol 490 (1) ◽

pp. L26-L31 ◽

Cited By ~ 2

Author(s):

Biny Sebastian ◽

P Kharb ◽

C P O’Dea ◽

J F Gallimore ◽

S A Baum

Keyword(s):

Magnetic Field ◽

Seyfert Galaxy ◽

Accretion Disc ◽

Field Structure ◽

Host Galaxy ◽

Very Large Array ◽

Rotation Measure ◽

A Minor ◽

The Magnetic Field ◽

East West

ABSTRACT We report the discovery of a secondary pair of radio lobes in the Seyfert galaxy NGC 2639 with polarization-sensitive observations with the Karl G. Jansky Very Large Array (VLA). The presence of these lobes, which are aligned nearly perpendicular to the known set of radio lobes observed in the east–west direction, has not been reported previously in the literature. The in-band rotation measure image shows gradients in both the lobes indicative of organized magnetic field structures on kpc-scales. The magnetic field structure is aligned with the jet/lobe direction in both the lobes. Based on the settled optical morphology of the host galaxy, it is likely that a minor merger that did not disrupt the host galaxy structure is responsible for the observed features in NGC 2639. This also explains the near 90° change in the jet direction; the current jet direction being the result of a new accretion disc formed by the minor merger, whose direction was a result of the angular momentum of the inflowing merger gas.

Download Full-text

Polarization study of the pulsars in the globular cluster 47 Tucanae

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317008389 ◽

2017 ◽

Vol 13 (S337) ◽

pp. 295-298

Author(s):

F. Abbate ◽

A. Possenti ◽

C. Tiburzi ◽

W. van Straten ◽

E. Barr ◽

...

Keyword(s):

Magnetic Field ◽

Globular Cluster ◽

Galactic Disk ◽

Line Of Sight ◽

Radio Telescopes ◽

Parallel Component ◽

Polarization Study ◽

Rotation Measure ◽

Linearly Polarized ◽

The Magnetic Field

AbstractThe linearly polarized component of a pulsar signal at different radio frequencies can help to constrain the parallel component of the magnetic field along the line of sight. In this work we measured the polarimetric properties of the pulsars in the globular cluster 47 Tucanae and we report the Rotation Measure (RM) for 13 of them. A gradient in the RM values of the pulsars across the cluster is detected suggesting the presence of significant variations in the magnetic field across the very small angular scales associated with the lines of sight to the pulsars in 47 Tucanae. Both magnetic fields located in the globular cluster or in the Galactic disk in the direction of the cluster are taken into consideration. However, more detailed modelling of the dynamics of the cluster and deeper observations with the MeerKAT and/or the SKA1 radio telescopes are necessary to discriminate among the models.

Download Full-text

WIDEBAND VERY LARGE ARRAY OBSERVATIONS OF A2256. I. CONTINUUM, ROTATION MEASURE, AND SPECTRAL IMAGING

The Astrophysical Journal ◽

10.1088/0004-637x/794/1/24 ◽

2014 ◽

Vol 794 (1) ◽

pp. 24 ◽

Cited By ~ 38

Author(s):

Frazer N. Owen ◽

Lawrence Rudnick ◽

Jean Eilek ◽

Urvashi Rau ◽

Sanjay Bhatnagar ◽

...

Keyword(s):

Spectral Imaging ◽

Large Array ◽

Very Large Array ◽

Rotation Measure

Download Full-text

Connecting magnetic fields from sub-galactic scale to clusters of galaxies and beyond with cosmological MHD simulations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316006396 ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 699-699

Author(s):

Klaus Dolag ◽

Alexander M. Beck ◽

Alexander Arth

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Heat Transport ◽

Galaxy Clusters ◽

Large Scale ◽

High Redshift ◽

Galactic Halos ◽

Rotation Measure ◽

The Magnetic Field ◽

Good Agreement

AbstractUsing the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

Download Full-text

Probing interstellar magnetic fields with Supernova remnants

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309030087 ◽

2008 ◽

Vol 4 (S259) ◽

pp. 75-80 ◽

Cited By ~ 2

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.

Download Full-text

Magnetic field evolution in dwarf and Magellanic-type galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730566 ◽

2018 ◽

Vol 611 ◽

pp. A7 ◽

Cited By ~ 1

Author(s):

H. Siejkowski ◽

M. Soida ◽

K. T. Chyży

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Large Scale ◽

Magnetic Energy ◽

Galactic Disk ◽

Cosmic Ray ◽

Dark Matter Halo ◽

Field Evolution ◽

Low Mass ◽

The Magnetic Field

Aims. Low-mass galaxies radio observations show in many cases surprisingly high levels of magnetic field. The mass and kinematics of such objects do not favour the development of effective large-scale dynamo action. We attempted to check if the cosmic-ray-driven dynamo can be responsible for measured magnetization in this class of poorly investigated objects. We investigated how starburst events on the whole, as well as when part of the galactic disk, influence the magnetic field evolution. Methods. We created a model of a dwarf/Magellanic-type galaxy described by gravitational potential constituted from two components: the stars and the dark-matter halo. The model is evolved by solving a three-dimensional (3D) magnetohydrodynamic equation with an additional cosmic-ray component, which is approximated as a fluid. The turbulence is generated in the system via supernova explosions manifested by the injection of cosmic-rays. Results. The cosmic-ray-driven dynamo works efficiently enough to amplify the magnetic field even in low-mass dwarf/Magellanic-type galaxies. The e-folding times of magnetic energy growth are 0.50 and 0.25 Gyr for the slow (50 km s−1) and fast (100 km s−1) rotators, respectively. The amplification is being suppressed as the system reaches the equipartition level between kinetic, magnetic, and cosmic-ray energies. An episode of star formation burst amplifies the magnetic field but only for a short time while increased star formation activity holds. We find that a substantial amount of gas is expelled from the galactic disk, and that the starburst events increase the efficiency of this process.

Download Full-text

Cosmic ray driven dynamo in barred and ringed galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311007368 ◽

2010 ◽

Vol 6 (S274) ◽

pp. 398-400

Author(s):

K. Kulpa-Dybeł ◽

K. Otmianowska-Mazur ◽

B. Kulesza-Żydzik ◽

G. Kowal ◽

D. Wóltański ◽

...

Keyword(s):

Magnetic Field ◽

Radio Emission ◽

High Frequency ◽

Galactic Disk ◽

Cosmic Ray ◽

Field Configuration ◽

Magnetic Field Configuration ◽

Global Evolution ◽

Weak Magnetic Fields ◽

The Magnetic Field

AbstractWe study the global evolution of the magnetic field and interstellar medium (ISM) of the barred and ringed galaxies in the presence of non-axisymmetric components of the potential, i.e. the bar and/or the oval perturbations. The magnetohydrodynamical dynamo is driven by cosmic rays (CR), which are continuously supplied to the disk by supernova (SN) remnants. Additionally, weak, dipolar and randomly oriented magnetic field is injected to the galactic disk during SN explosions. To compare our results directly with the observed properties of galaxies we construct realistic maps of high-frequency polarized radio emission. The main result is that CR driven dynamo can amplify weak magnetic fields up to few μG within few Gyr in barred and ringed galaxies. What is more, the modelled magnetic field configuration resembles maps of the polarized intensity observed in barred and ringed galaxies.

Download Full-text

Reading M87's DNA: A Double Helix Revealing a Large-scale Helical Magnetic Field

The Astrophysical Journal ◽

10.3847/2041-8213/ac3a88 ◽

2021 ◽

Vol 923 (1) ◽

pp. L5

Author(s):

Alice Pasetto ◽

Carlos Carrasco-González ◽

José L. Gómez ◽

José-Maria Martí ◽

Manel Perucho ◽

...

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Double Helix ◽

High Sensitivity ◽

Polarization Degree ◽

Very Large Array ◽

Wide Range ◽

Helical Magnetic Field ◽

Helical Configuration ◽

The Magnetic Field

Abstract We present unprecedented high-fidelity radio images of the M87 jet. We analyzed Jansky Very Large Array broadband full-polarization radio data from 4 to 18 GHz. The observations were taken with the most extended configuration (A configuration), which allows the study of the emission of the jet up to kiloparsec scales with a linear resolution of ∼10 pc. The high sensitivity and resolution of our data allow us to resolve the jet width. We confirm a double-helix morphology of the jet material between ∼300 pc and ∼1 kpc. We found a gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges and a gradient in the Faraday depth with opposite signs at the jet edges. We also found that the behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All of these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole, although the jet is most likely particle-dominated at these large scales. Therefore, we propose a plausible scenario in which the helical configuration of the magnetic field has been maintained to large scales thanks to the presence of Kelvin–Helmholtz instabilities.

Download Full-text