J/A+A/639/A111 NGC 4217 radio and polarization maps (Stein+, 2020)
CHANG-ES XXI. Transport processes and the X-shaped magnetic field of NGC 4217:
off-center superbubble structure.
Stein Y., Dettmar R.-J., Beck R., Irwin J., Wiegert T., Miskolczi A.,
Wang Q.D., English J., Henriksen R., Radica M., L J.-T.
<Astron. Astrophys. 639, A111 (2020)>
=2020A&A...639A.111S 2020A&A...639A.111S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Radio continuum ; Magnetic fields ; Polarization
Keywords: galaxies: halos - polarization - galaxies: individual: NGC 4217 -
radio continuum: galaxies - galaxies: spiral -
galaxies: magnetic fields
Abstract:
We investigate the radio continuum halo, the magnetic field, and the
transport processes of the CRs of the edge-on spiral galaxy NGC 4217
using Continuum HAlos in Nearby Galaxies - an Evla Survey (CHANG-ES)
radio data at two frequencies, 6GHz (C-band) and 1.5GHz (L-band),
and supplemental LOFAR data of this galaxy at 150MHz. With additional
X-ray Chandra data, we study the connection of radio features to the
diffuse hot gas around NGC 4217.
NGC 4217 shows a large-scale X-shaped magnetic field structure,
covering a major part of the galaxy with a mean total magnetic field
strength in the disk of 9G. From the analysis of the rotation
measure map at C-band, we found that the direction of the disk
magnetic field is pointing inward. A helical outflow structure is
furthermore present in the northwestern part of the galaxy, which is
extended nearly 7 kpc into the halo. More polarized emission is
observed on the approaching side of the galaxy, indicating that
Faraday depolarization has to be considered at C-band. With a
simplified galaxy disk model, we are able to explain the finding of
higher polarized intensity on the approaching side. We generalize the
model to predict that roughly 75% of edge-on spiral galaxies will show
higher polarized intensity on the approaching side. Many loop and
shell structures are found throughout the galaxy in total intensity at
C-band. One structure, a symmetric off-center (to the southwest of the
disk) superbubble-like structure is prominent in total and polarized
intensity, as well as in Halpha and optical dust filaments. This is at
a location where a second peak of total intensity (to the southwest of
the disk) is observed, making this superbubble-like structure a
possible result of a concentrated star formation region in the disk.
The X-ray diffuse emission shows similarities to the polarized diffuse
emission of NGC 4217. The flux density extension of the radio
continuum halo increases toward lower frequencies. While the total
flux density of the disk and halo are comparable at C-band, the
contribution of the disk flux density decreases toward LOFAR to 18% of
the total flux density. Dumbbell-shaped structures are present at
C-band and at the LOFAR frequency. Total intensity profiles at the two
CHANG-ES bands and the LOFAR frequency show a clear two-component
behavior and were fit best with a two-component exponential fit. The
halo scale heights are 1.10±0.04kpc, 1.43±0.09kpc, and
1.55±0.04kpc in C-band, L-band, and 150MHz, respectively. The
frequency dependence of these scale heights between C-band and L-band
suggests advection to be the main transport process. The 1D CRE
transport modeling shows that advection appears to be more important
than diffusion.
Description:
We present the radio continuum data (6 cm/C-band and 20 cm/L-band) of
the galaxy NGC 4217 from the CHANG-ES survey, observed with the VLA.
We combined and analysed the data of the following five datasets:
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Dataset Observing Date Time on Source(before flagging)
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L-band B-configuration 11. Aug 2012 2 hr
L-band C-configuration 31. Mar 2012 30 min
L-band D-configuration 18. Dec 2012 20 min
C-band C-configuration 26. Feb 2012 3 hr
C-band D-configuration 27. Dec 2012 40 min
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Please see paper and Irwin et al. (2012AJ....144...43I 2012AJ....144...43I,
2012AJ....144...44I 2012AJ....144...44I) for details on the calibration and imaging.
The here presented fits-files are named in accordance to the figure in
the paper
Stokes I was imaged with robust zero weighting:
- Stokes I of combined (B-, C-, D-configuration) L-band, beam of
12.3"x13.4: Fig.1bN4217LcombStokesIrob0.pbcor.fits
- Stokes I of combined (C-, D-configuration) C-band, uv-tapering of 12
klambda, smoothed to 7.7"x7.7" beam:
Fig.1aN4217CcombStokesIuvtap12.pbcor.fits
- Stokes I C-configuration C-band, uv-tapering of 16 klambda, beam of
5.8"x5.9": Fig.2N4217CCStokesIuvtap16.pbcor.fits
- Stokes I of D-configuration L-band, smooth to 60.5"x60.5" beam:
Fig.12N4217DLStokesIrob0_smooth60.fits
Polarisation was imaged with rob two weighting:
a) combined (C-, D-configuration) C-band, images were all smoothed to
7.7"x7.7" beam
- Polarized Intensity (PI) from Stokes Q and U:
"Fig.11aN4217CcombPIrob2_smooth7.fits"
- Polarized Angle (PA) from Stokes Q and U:
"Fig.11aN4217CcombPArob2_smooth7.fits"
- Polarized Intensity (PI rmsynth) from RM-synthesis:
Fig.11bN4217CcombPIrmsynthrob2smooth7.fits
- Derotated Polarized Angle (PA0 rmsynth) from RM-synthesis:
Fig.11bN4217CcombPA0rmsynthrob2smooth7.fits
b) D-configuration L-band: smooth to 60.5"x60.5" beam
- Polarized Intensity (PI) from Stokes Q and U:
Fig.12aN4217DLPIrob2_smooth60.fits
- Polarized Angle (PA) from Stokes Q and U:
Fig.12aN4217DLPArob2_smooth60.fits
- Polarized Intensity (PI rmsynth) from RM-synthesis:
Fig.12bN4217DLPIrmsynthrob2smooth60.fits
- Derotated Polarized Angle (PA0 rmsynth) from RM-synthesis:
Fig.12bN4217DLPA0rmsynthrob2smooth60.fits
RM map at C-band:
- RM map created with RM-synthesis, beam of 13"x13", rotated version
of this shown in the paper: N4217RMmaprmsynth.fits
Objects:
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RA (2000) DE Designation(s)
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12 15 50.90 +47 05 30.4 NGC 4217 = UGC 7282
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 232 13 List of fits images
fits/* . 13 Individual fits images
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See also:
J/AJ/150/81 : CHANG-ES. IV. VLA D-configuration observations (Wiegert+, 2015)
J/A+A/623/A33 : NGC 4666 polarization maps (Stein+, 2019)
J/A+A/632/A10 : NGC 4631 total intensity images (Mora-Partiarroyo+, 2019)
J/A+A/632/A11 : Radio images of NGC 4631 (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
--------------------------------------------------------------------------------
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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 46 A19 "datime" Obs.date Observation date
48- 51 I4 Kibyte size Size of FITS file
53-101 A49 --- FileName Name of FITS file, in subdirectory fits
103-232 A130 --- Title Title of the FITS file
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Acknowledgements:
Yelena Stein, yelena.stein(at)astro.unistra.fr
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, Cat. J/AJ/150/81
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
Mora-Partiarroyo et al., Paper XV 2019A&A...632A..11M 2019A&A...632A..11M, Cat. J/A+A/632/A11
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) Yelena Stein [Strasbourg Obs.], Patricia Vannier [CDS] 12-Jun-2020