J/MNRAS/467/1776 Faraday rotation in Magellanic Bridge (Kaczmarek+, 2017)
Detection of a coherent magnetic field in the Magellanic Bridge through
Faraday rotation.
Kaczmarek J.F., Purcell C.R., Gaensler B.M., McClure-Griffiths N.M.,
Stevens J.
<Mon. Not. R. Astron. Soc. 467, 1776 (2017)>
=2017MNRAS.467.1776K 2017MNRAS.467.1776K (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Magnetic fields ; Polarization
Keywords: polarization - Magellanic Clouds - galaxies: magnetic fields
Abstract:
We present an investigation into the magnetism of the Magellanic
Bridge, carried out through the observation of Faraday rotation
towards 167 polarized extragalactic radio sources spanning the
continuous frequency range of 1.3-3.1GHz with the Australia Telescope
Compact Array. Comparing measured Faraday depth values of sources
'on' and 'off' the Bridge, we find that the two populations
are implicitly different. Assuming that this difference in populations
is due to a coherent field in the Magellanic Bridge, the observed
Faraday depths indicate a median line-of-sight coherent magnetic-field
strength of B||~=0.3uG directed uniformly away from us. Motivated by
the varying magnitude of Faraday depths of sources on the Bridge, we
speculate that the coherent field observed in the Bridge is a
consequence of the coherent magnetic fields from the Large and Small
Magellanic Clouds being pulled into the tidal feature. This is the
first observation of a coherent magnetic field spanning the entirety
of the Magellanic Bridge and we argue that this is a direct probe of a
'pan-Magellanic' field.
Description:
For this investigation, we observed a subset of polarized sources that
were originally identified through the reduction and re-processing of
archival continuum data of the western MB (see Muller et al.
2003MNRAS.339..105M 2003MNRAS.339..105M) for a summary of observations).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 71 167 Table of the Faraday depth values for each
polarized source used in our analysis
--------------------------------------------------------------------------------
See also:
J/MNRAS/339/105 : Western Magellanic Bridge HI observations (Muller+, 2003)
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Note [*] Note (1)
3- 9 F7.3 deg GLON Galactic longitude
11- 17 F7.3 deg GLAT Galactic latitude
19- 23 D5.3 % P0 Intrinsic polarization fraction
25- 29 F5.3 % e_P0 rms uncertainty on P0 (1σ)
31- 35 F5.1 deg psi0 Intrinsic polarization angle
37- 40 F4.1 deg e_psi0 rms uncertainty on psi0 (1σ)
42- 46 F5.1 rad/m2 phiraw Observed Faraday depth
48- 51 F4.1 rad/m2 e_phiraw rms uncertainty on phiraw (1σ)
53- 56 F4.1 rad/m2 sigmaphi Faraday dispersion
58- 60 F3.1 rad/m2 e_sigmaphi rms uncertainty on sigmaphi (1σ)
62- 66 F5.1 rad/m2 phicorr Faraday depth of each source once the Faraday
rotation due to the MW foreground has been
corrected for
68- 71 F4.1 rad/m2 e_phicorr rms uncertainty on phicorr
--------------------------------------------------------------------------------
Note (1): * indicates x targets that are considered to be off the Bridge,
otherwise sources are considered to be on-Bridge sources.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Nov-2019