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J/A+A/600/A6   NGC628 3.1GHz total intensity & polarised images (Mulcahy+, 2017)

Resolved magnetic structures in the disk-halo interface of NGC 628. Mulcahy D.D., Beck R., Heald G. <Astron. Astrophys. 600, A6 (2017)> =2017A&A...600A...6M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Radio lines ; Polarization Keywords: cosmic rays - galaxies: magnetic fields - galaxies: ISM - radio continuum: galaxies Abstract: Magnetic fields are essential to fully understand the interstellar medium (ISM) and its role in the disk-halo interface of galaxies is still poorly understood. Star formation is known to expel hot gas vertically into the halo and these outflows have important consequences for mean-field dynamo theory in that they can be efficient in removing magnetic helicity. We perform new observations of the nearby face-on spiral galaxy NGC 628 with the Karl G. Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at frequencies of 2.6GHz and 8.35GHz. We obtain some of the most sensitive radio continuum images in both total and linearly polarised intensity of any external galaxy observed so far in addition to high-quality images of Faraday depth and polarisation angle from which we obtained evidence for drivers of magnetic turbulence in the disk-halo connection. Such drivers include a superbubble detected via a significant Faraday depth gradient coinciding with a HI hole. We observe an azimuthal periodic pattern in Faraday depth with a pattern wavelength of 3.7±0.1kpc, indicating Parker instabilities. The lack of a significant anti-correlation between Faraday depth and magnetic pitch angle indicates that these loops are vertical in nature with little helical twisting, unlike in IC 342. We find that the magnetic pitch angle is systematically larger than the morphological pitch angle of the polarisation arms which gives evidence for the action of a large-scale dynamo where the regular magnetic field is not coupled to the gas flow and obtains a significant radial component. We additionally discover a lone region of ordered magnetic field to the north of the galaxy with a high degree of polarisation and a small pitch angle, a feature that has not been observed in any other galaxy so far and is possibly caused by an asymmetric HI hole. Description: Total Intensity and polarised intensity/angle images of NGC628 with the S-Band (3-4GHz) receiver of the JVLA at natural (18arcsec) and robust weighting(7.5-arcsec). Full details of the observation, calibration and imaging can be seen in the paper. Objects: ----------------------------------------- RA (2000) DE Designation(s) ----------------------------------------- 01 36 41.77 +15 47 00.5 NGC628 = M 74 ----------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file list.dat 170 6 List of fits images fits/* 0 6 Individual fits images
Byte-by-byte Description of file: list.dat
Bytes Format Units Label Explanations
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000) 10- 18 F9.5 deg DEdeg Declination of center (J2000) 20- 23 I4 --- Nx Number of pixels along X-axis 25- 28 I4 --- Ny Number of pixels along Y-axis 30- 50 A21 --- Obs.Date Observatrion date (YYYY-MM-DDThh:mm:ss.s) 52- 58 F7.5 GHz Freq observed frequency 60- 64 I5 Kibyte size Size of FITS file 66- 87 A22 --- FileName Name of FITS file, in subdirectory fits 89-170 A82 --- Title Title of the FITS file
Acknowledgements: David Mulcahy, david.mulcahy(at)
(End) Patricia Vannier [CDS] 23-Feb-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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