Large-scale radio continuum properties of 19 Virgo cluster galaxies

Vollmer, B.; Soida, M.; Beck, Rainer; Chung, A.; Urbanik, M.; Chyży, K. T.; Otmianowska-Mazur, K.; Kenney, Jeffrey D. P.

doi:10.1051/0004-6361/201321163

Cited by 55 publications

(70 citation statements)

References 62 publications

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“…the radial velocities are positive). Similar DP asymmetries along the major axis of the projected galaxy disk in the sky plane were found in many other galaxies, for which the minimum polarized emission at λ20 cm owing to strong depolarization is always located on the receding side (Braun et al 2010;Vollmer et al 2013). A combination of spiral fields in the disk and vertical fields in the halo, as observed in edge-on galaxies (Krause 2014) and predicted by dynamo models (i.e.…”

Section: Faraday Depolarizationsupporting

confidence: 75%

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study

Beck

2015

A&A

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Context. Magnetic fields play an important role in the formation and stabilization of spiral structures in galaxies, but the interaction between interstellar gas and magnetic fields has not yet been understood. In particular, the phenomenon of "magnetic arms" located between material arms is a mystery. Aims. The strength and structure of interstellar magnetic fields and their relation to spiral arms in gas and dust are investigated in the nearby and almost face-on spiral galaxy IC 342. Methods. The total and polarized radio continuum emission of IC 342 was observed with high spatial resolution in four wavelength bands with the Effelsberg and VLA telescopes. At λ6.2 cm the data from both telescopes were combined. I separated thermal and nonthermal (synchrotron) emission components with the help of the spectral index distribution and derived maps of the magnetic field strength, degree of magnetic field order, magnetic pitch angle, Faraday rotation measure, and Faraday depolarization. Results. IC 342 hosts a diffuse radio disk with an intensity that decreases exponentially with increasing radius. The frequency dependence of the scalelength of synchrotron emission indicates energy-dependent propagation of the cosmic-ray electrons, probably via the streaming instability. The equipartition strength of the total field in the main spiral arms is typically 15 μG, that of the ordered field about 5 μG. The total radio emission, observed with the VLA's high resolution, closely follows the dust emission in the infrared at 8 μm (Spitzer telescope) and 22 μm (WISE telescope). The polarized emission is not diffuse, but concentrated in spiral arms of various types: (1) a narrow arm of about 300 pc width, displaced inwards with respect to the eastern arm by about 200 pc, indicating magnetic fields compressed by a density wave; (2) a broad arm of 300-500 pc width around the northern arm with systematic variations in polarized emission, polarization angles, and Faraday rotation measures on a scale of about 2 kpc, indicative of a helically twisted flux tube generated by the Parker instability; (3) a rudimentary magnetic arm in an interarm region in the north-west; (4) several broad spiral arms in the outer galaxy, related to spiral arms in the total neutral gas; (5) short features in the outer south-western galaxy, probably distorted by tidal interaction. Faraday rotation of the polarization angles reveals an underlying regular field of only 0.5 μG strength with a large-scale axisymmetric spiral pattern, probably a signature of a mean-field α − Ω dynamo, and an about 10× stronger field that fluctuates on scales of a few 100 pc. The magnetic field around the bar in the central region of IC 342 resembles that of large barred galaxies; it has a regular spiral pattern with a large pitch angle, is directed outwards, and is opposite to the large-scale regular field in the disk. Polarized emission at λ20.1 cm is strongly affected by Faraday depolarization in the western and northern parts of the galaxy. Helical fields extending fro...

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Section: Faraday Depolarizationsupporting

confidence: 75%

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study

Beck

2015

A&A

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“…Radio continuum observations of other Virgo galaxies affected by ram pressure like NGC 4402 or NGC 4501 also show signs of interaction with the ICM: both galaxies show a truncated gas disk (Chung et al 2009) with enhancements of polarization and sharp edges of the total power emission on one side of the galactic disk (Vollmer et al 2007. Vollmer et al (2008) estimated a ram pressure of P ≈ 8.2 × 10 −12 dyn cm −2 for NGC 4501.…”

Section: Ram Pressure Estimatesmentioning

confidence: 98%

“…The distribution of polarized radio emission in a cluster galaxy tends to be asymmetric as a consequence of interaction with the ICM (Vollmer et al 2007(Vollmer et al , 2013. This interaction enhances the polarized flux on the side which is facing the ram pressure due to the motion of the galactic disk in the denser environment.…”

Section: Introductionmentioning

confidence: 99%

Chang-Es. Vii. Magnetic Outflows From the Virgo Cluster Galaxy NGC 4388

Damas-Segovia

Beck

Vollmer

et al. 2016

ApJ

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We investigate the effects of ram pressure on the ordered magnetic field of a galaxy hosting a radio halo and strong nuclear outflows. New radio images in total and polarized intensity of the edge-on Virgo galaxy NGC 4388 were obtained within the CHANG-ES EVLA project. The unprecedented noise level reached allows us to detect striking new features of the ordered magnetic field. The nuclear outflow extends far into the halo to about 5 kpc from the center and is spatially correlated with the Hα and X-ray emission. For the first time, the southern outflow is detected. Above and below both spiral arms we find extended blobs of polarized emission with an ordered field oriented perpendicular to the disk. The synchrotron lifetime of the cosmic ray electrons (CREs) in these regions yields a mean outflow velocity of (270 ± 70) km s −1 , in agreement with a galactic wind scenario. The observed symmetry of the polarized halo features in NGC 4388 excludes a compression of the halo gas by the ram pressure of the intra-cluster medium (ICM). The assumption of equilibrium between the halo pressure and the ICM ram pressure yields an estimate of the ICM density that is consistent with both the ICM density derived from X-ray observations and the recent Planck Sunyaev-Zel'dovich measurements. The detection of a faint radio halo around cluster galaxies could thus be used for an estimate of ICM ram pressure.

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“…Due to the substantial depolarization in the midplane of star-forming galaxies (e.g. Braun et al 2007;Vollmer et al 2013, in the WSRT-SINGS survey and in the Virgo cluster, respectively), only the front layer of the ISM is visible in polarization as could be expected from internal Faraday dispersion (Sokoloff et al 1998). This depolarization, together with a common large-scale magnetic field topology, leads to a clear and consistent pattern within the sample: an azimuthal variation in fractional polarization exhibiting a minimum at the kinematically receding major axis, together with an azimuthal variation in the rotation measure.…”

Section: Large-scale Field Structuresmentioning

confidence: 99%

Magnetic Field Tomography in Nearby Galaxies with the Square Kilometre Array

Heald¹,

Beck²,

Blok³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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Magnetic fields play an important role in shaping the structure and evolution of the interstellar medium (ISM) of galaxies, but the details of this relationship remain unclear. With SKA1, the 3D structure of galactic magnetic fields and its connection to star formation will be revealed. A highly sensitive probe of the internal structure of the magnetoionized ISM is the partial depolarization of synchrotron radiation from inside the volume. Different configurations of magnetic field and ionized gas within the resolution element of the telescope lead to frequency-dependent changes in the observed degree of polarization. The results of spectro-polarimetric observations are tied to physical structure in the ISM through comparison with detailed modeling, supplemented with the use of new analysis techniques that are being actively developed and studied within the community such as Rotation Measure Synthesis. The SKA will enable this field to come into its own and begin the study of the detailed structure of the magnetized ISM in a sample of nearby galaxies, thanks to its extraordinary wideband capabilities coupled with the combination of excellent surface brightness sensitivity and angular resolution.Advancing Astrophysics with the Square Kilometre Array

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Large-scale radio continuum properties of 19 Virgo cluster galaxies

Cited by 55 publications

References 62 publications

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study

Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study

Chang-Es. Vii. Magnetic Outflows From the Virgo Cluster Galaxy NGC 4388

Magnetic Field Tomography in Nearby Galaxies with the Square Kilometre Array

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