J/A+A/660/A48 Western lobe of Fornax A images (Loi+, 2022)
A depolarizing HI tidal tail in the western lobe of Fornax A.
Loi F., Serra P., Murgia M., Govoni F., Anderson C., Heald G., Kleiner D.,
Lenc E., Vacca V., Maccagni M., Dettmar R.J.
<Astron. Astrophys. 660, A48 (2022)>
=2022A&A...660A..48L 2022A&A...660A..48L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; H I data ; Polarization
Keywords: magnetic fields - methods: observational - polarization -
galaxies: groups: individual: Fornax A - radio lines: galaxies -
radio continuum: galaxies
Abstract:
Recent MeerKAT neutral hydrogen (HI) observations of Fornax A reveal
tidal material intersecting in projection the western lobe of this
radio galaxy. We found a spatial coincidence between the northern HI
tail and a depolarized structure observed for the first time with the
Australian Square Kilometre Array Pathfinder (ASKAP) at 1.2GHz. We
analyzed the properties of the rotation measure (RM) image obtained
with ASKAP data at the location of the HI tail and in its
neighborhood. We modeled the observed RM structure function to
investigate the magnetic field power spectrum at the location of the
HI tail and in a nearby control region. We found that the observed RM,
in the control region and in a region enclosing the HI tail, cannot be
due to the intracluster Faraday screen caused by the Fornax cluster.
An intragroup magnetized medium with a central magnetic field strength
of 18.5uG can explain the control region RM, but it is clear that
there is an excess in correspondence with the HI tail region. We
evaluated several scenarios in which the HI tail is either in the lobe
foreground or embedded in the lobe. We determined a magnetic field
strength on the order of ∼9.5-11uG in the HI tail, a value consistent
with constraints derived from narrowband Hα imaging of the
ionized gas. The spatial coincidence between HI tail and
depolarization analyzed in this paper could be the first observed
evidence of a magnetic field that either has passed through a radio
galaxy lobe or has survived the lobe expansion.
Description:
MeerKAT HI image, ASKAP polarization and RM images.
Objects:
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RA (2000) DE Designation(s)
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03 22 41.79 -37 12 29.5 Fornax A = NGC 1316
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 97 3 List of fits images
fits/* . 3 Individual fits images
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See also:
J/ApJ/645/256 : XMM observations of Fornax A (NGC 1316) (Isobe+, 2006)
J/MNRAS/461/4260 : NGC1316 (Fornax A) g'r'i' photometry (Sesto+, 2016)
J/A+A/656/A45 : Feeding and feedback in Fornax A (Maccagni+, 2021)
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- 23 F4.2 arcsec/pix scale ? Scale of the image
25- 28 I4 --- Nx Number of pixels along X-axis
30- 33 I4 --- Ny Number of pixels along Y-axis
35- 55 A21 "datime" Obs.date Observation date
57- 61 I5 Kibyte size Size of FITS file
63- 72 A10 --- FileName Name of FITS file, in subdirectory fits
74- 97 A24 --- Title Title of the FITS file
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Acknowledgements:
Francesca Loi, francesca.loi(at)inaf.it
(End) Patricia Vannier [CDS] 27-Feb-2022