J/A+A/632/A11 Radio images of NGC 4631 (Mora-Partiarroyo+, 2019)
CHANG-ES. XV. Large-scale magnetic field reversals in the radio halo of
NGC 4631.
Mora-Partiarroyo S.C., Krause M., Basu A., Beck R., Wiegert T., Irwin J.,
Henriksen R., Stein Y., Vargas C.J., Heesen V., Walterbos R.A.M.,
Rand R.J., Heald G., Li J., Kamieneski P., English J.
<Astron. Astrophys. 632, A11 (2019)>
=2019A&A...632A..11M 2019A&A...632A..11M (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Radio continuum
Keywords: galaxies: individual: NGC 4631 - galaxies: halos -
galaxies: magnetic fields - galaxies: interactions -
galaxies: spiral - radio continuum: galaxies
Abstract:
NGC 4631 is an interacting galaxy which exhibits one of the largest
gaseous halos observed among edge-on galaxies. We aim to examine the
synchrotron and polarization properties of its disk and halo emission
with new radio continuum data.
Radio continuum observations of NGC 4631 were performed with the Karl
G. Jansky Very Large Array at C-band (5.99GHz) in the C & D array
configurations, and at L-band (1.57GHz) in the B, C, & D array
configurations. The Rotation Measure Synthesis algorithm was utilized
to derive the polarization properties.
We detected linearly polarized emission at C-band and L-band. The
magnetic field in the halo is characterized by strong vertical
components above and below the central region of the galaxy. The
magnetic field in the disk is only clearly seen in the eastern side of
NGC 4631, where it is parallel to the plane of the major axis of the
galaxy. We detected for the first time a large-scale, smooth Faraday
depth pattern in a halo of an external spiral galaxy, which implies
the existence of a regular (coherent) magnetic field. A quasi-periodic
pattern in Faraday depth with field reversals was found in the
northern halo of the galaxy.
The field reversals in the northern halo of NGC 4631, together with
the observed polarization angles, indicate giant magnetic ropes (GMRs)
with alternating directions. To our knowledge, this is the first time
such reversals are observed in an external galaxy.
Description:
Radio polarimetric observations of NGC 4631 were performed with the
Karl G. Jansky Very Large Array (VLA) during its commissioning phase
through the project Continuum HAlos in Nearby Galaxies - an EVLA
Survey (CHANG-ES). The data were taken at C-band (5.0-7.0GHz) in C
and D array configuration, and at L-band (1.25-1.50 and
1.65-1.90GHz) in the B, C, and D array configurations.
We present polarized intensity images of NGC4631.
Objects:
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RA (2000) DE Designation(s)
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12 42 08.01 +32 32 29.4 NGC 4631 = UGC 7865
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 169 2 List of fits images
fits/* . 2 Individual fits images
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See also:
J/A+A/623/A33 : NGC 4666 polarization maps (Stein+, 2019)
J/A+a/632/A10 : NGC 4631 radio emission maps (Mora Partiarroyo+, 2019)
J/A+A/632/A12 : NGC 891 and NGC 4565 radio images (Schmidt+, 2019)
J/A+A/632/A13 : NGC 4013 radio and polarization maps (Stein+, 2019)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 53 A26 "datime" Obs.Date Observation date
55- 58 I4 Kibyte size Size of FITS file
60- 80 A21 --- FileName Name of FITS file, in subdirectory fits
82-169 A88 --- Title Title of the FITS file
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Acknowledgements:
Silvia Carolina Mora Partiarroyo, silvia.carolina.mora(at)gmail.com
References:
Irwin et al., Paper I 2012AJ....144...43I 2012AJ....144...43I
Irwin et al., Paper II 2012AJ....144...44I 2012AJ....144...44I
Irwin et al., Paper III 2013AJ....146..164I 2013AJ....146..164I
Wiegert et al., Paper IV 2015AJ....150...81W 2015AJ....150...81W
Irwin et al., Paper V 2015ApJ...809..172I 2015ApJ...809..172I
Li et al., Paper VI 2016MNRAS.456.1723L 2016MNRAS.456.1723L
Damas-Segovia et al., Paper VII 2016ApJ...824...30D 2016ApJ...824...30D
Irwin et al., Paper VIII 2017MNRAS.464.1333I 2017MNRAS.464.1333I
Krause et al., Paper IX 2018A&A...611A..72K 2018A&A...611A..72K
Vargas et al., Paper X 2018ApJ...853..128V 2018ApJ...853..128V
Irwin et al., Paper XI 2018MNRAS.476.5057I 2018MNRAS.476.5057I
Miskolczi et al., Paper XII 2019A&A...622A...9M 2019A&A...622A...9M
Stein et al., Paper XIII 2019A&A...623A..33S 2019A&A...623A..33S, Cat. J/A+A/623/A33
Mora Partiarroyo et al., Paper XIV 2019A&A...632A..10M 2019A&A...632A..10M, Cat. J/A+A/632/A10
Schmidt et al., Paper XVI 2019A&A...632A..12S 2019A&A...632A..12S, Cat. J/A+A/632/A12
Vargas et al., Paper XVII 2019ApJ...881...26V 2019ApJ...881...26V
Stein et al., Paper XIX 2019A&A...632A..13S 2019A&A...632A..13S, Cat. J/A+A/632/A13
Irwin et al., Paper XX 2019AJ....158...21I 2019AJ....158...21I
(End) Patricia Vannier [CDS] 10-Sep-2019