The magnetic fields of large Virgo cluster spirals. II

Weżgowiec, M.; Urbanik, M.; Beck, Rainer; Chyży, K. T.; Soida, M.

doi:10.1051/0004-6361/201218871

Cited by 15 publications

(16 citation statements)

References 38 publications

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“…6 of that paper) are markedly displaced from the optical image towards the west. This displacement has been confirmed by observations at 3.6 cm wavelength (Weżgowiec et al 2012) galactic dynamo is compressed on the western side by ram pressure; (2) a weakening of the galactic dynamo on the eastern side by ram pressure; (3) amplification and ordering of the magnetic field by shear in the HI envelope of the galaxy (Vollmer et al 2010). Note that NGC 4535 is observed almost face-on, so that if the asymmetry in PI is due to ram pressure effects then its motion through the intracluster medium (ICM) is expected to be at a small or moderate angle with respect to the galactic plane; in this case the direction of motion can hardly be inferred from spectroscopic data which gives radial velocities.…”

Section: Introductionsupporting

confidence: 81%

“…Displacements towards one side of the disc are also detected in other galaxies observed edge-on, e.g. in NGC 4402 ) and in NGC 4388 (Weżgowiec et al 2012). On the other hand, several face-on galaxies of the Virgo Cluster with large-scale spiral patterns of their magnetic fields, like NGC 4303 and NGC 4321, show no displacement at all, presumably indicating that they move "head-on" through the cluster medium, i.e.…”

Section: Introductionmentioning

confidence: 83%

“…On the other hand, several face-on galaxies of the Virgo Cluster with large-scale spiral patterns of their magnetic fields, like NGC 4303 and NGC 4321, show no displacement at all, presumably indicating that they move "head-on" through the cluster medium, i.e. almost along the line of sight (Weżgowiec et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Ram pressure effects in the galactic plane and galactic dynamos in the no-zapproximation

Moss

Sokoloff

Beck

2012

A&A

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Context. The magnetic field of galaxies is believed to be produced by internal dynamo action, but can be affected by motion of the galaxy through the surrounding medium. Observations of polarized radio emission of galaxies located in galaxy clusters have revealed noticeable features of large-scale magnetic configurations, including displacements of the magnetic structures from the optical images and tails, which are possible imprints of ram pressure effects arising from motion of the galaxies through the intracluster medium. Aims. We present a quantitative dynamo model, which attempts to describe the above effects. In contrast, to the traditional problem of a wind affecting a body with a prescribed magnetic field, we investigate how a non-magnetized wind flow affects a magnetic field that is being self-excited by galactic dynamo action. Methods. To isolate the leading physical effects, we exploit a simple dynamo model that can describe relevant effects. In particular, we use what is known as the "no-z" approximation for the mean-field dynamo equations. Results. In a suitable parametric range we obtain displacements of the large-scale magnetic field, as well as magnetic tails. However, the specific details of their locations are quite counterintuitive. The direction of displacement is perpendicular to, rather than parallel to, the wind direction. The point at which the tail emerges from the galaxy depends on details of the model. The tail is eventually directed downstream. In the simplest case the magnetic tail begins in the region where the wind decreases the total gas velocity. Any wind that penetrates the galaxy modifies the intrinsic dynamo action. These features are different from those found in ram-pressure models. Conclusions. Any determination of galactic motion through the cluster medium from observational data needs to take the effects of dynamo action into account.

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Section: Introductionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 83%

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Ram pressure effects in the galactic plane and galactic dynamos in the no-zapproximation

Moss

Sokoloff

Beck

2012

A&A

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“…The Virgo cluster is a location of especially strong interaction effects (Fig. 22), and almost all cluster galaxies observed so far show asymmetries of their polarized emission because the outer magnetic fields were compressed (Vollmer et al , 2013Weżgowiec et al 2007Weżgowiec et al , 2012. Ordered fields are an excellent tracer of past interactions between galaxies or with the intergalactic medium.…”

Section: Beyond Spirals: Interacting Galaxiesmentioning

confidence: 99%

Magnetic fields in spiral galaxies

Beck¹

2015

Astron Astrophys Rev

368

269

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Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 μG) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.-Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edgeon galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young

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“…18.11 and 18.12), and almost all cluster galaxies observed so far show asymmetries of their polarized emission because the outer magnetic fields were compressed (Vollmer et al , 2013Weżgowiec et al 2007Weżgowiec et al , 2012. The Virgo cluster is a location of especially strong interaction effects (Figs.…”

Section: Interacting Galaxiesmentioning

confidence: 93%