J/A+A/622/A196 GMVA 86GHz Stokes IQU images of 3C84 jet (Kim+, 2019)
Spatially resolved origin of mm-wave linear polarization in the nuclear
region of 3C 84.
Kim J.-Y., Krichbaum, T.P., Marscher, A.P., Jorstad S.G., Agudo I.,
Thum C., Hodgson J.A., MacDonald N.R., Ros E., Lu R.-S., Bremer M.,
de Vicente P., Lindqvist M., Trippe S., Zensus J.A.
<Astron. Astrophys. 622, A196 (2019)>
=2019A&A...622A.196K 2019A&A...622A.196K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, radio ; Interferometry ; Polarization
Keywords: galaxies: active - galaxies: jets -
galaxies: individual : NGC 1275 - galaxies: individual : 3C 84 -
techniques : interferometric, polarimetric
Abstract:
We report results from a deep polarization imaging of the nearby radio
galaxy 3C 84 (NGC 1275). The source was observed with the Global
Millimeter VLBI Array (GMVA) at 86GHz at an ultrahigh angular
resolution of 50µas (corresponding to 200Rs). We also add
complementary multiwavelength data from the Very Long Baseline Array
(VLBA; 15 & 43GHz) and from the Atacama Large Millimeter/submillimeter
Array (ALMA; 97.5, 233.0, and 343.5GHz). At 86GHz, we measured a
fractional linear polarization of ∼2% in the VLBI core region. The
polarization morphology suggests that the emission is associated with
an underlying limb-brightened jet. The fractional linear polarization
is lower at 43 and 15GHz (∼0.3-0.7% and <0.1%, respectively). This
suggests an increasing linear polarization degree toward shorter
wavelengths on VLBI scales. We also obtain a large rotation measure
(RM) of ∼105-6rad/m2 in the core at ≳43GHz. Moreover, the VLBA
43GHz observations show a variable RM in the VLBI core region during
a small flare in 2015. Faraday depolarization and Faraday conversion
in an inhomogeneous and mildly relativistic plasma could explain the
observed linear polarization characteristics and the previously
measured frequency dependence of the circular polarization. Our
Faraday depolarization modeling suggests that the RM most likely
originates from an external screen with a highly uniform RM
distribution. To explain the large RM value, the uniform RM
distribution, and the RM variability, we suggest that the Faraday
rotation is caused by a boundary layer in a transversely stratified
jet. Based on the RM and the synchrotron spectrum of the core, we
provide an estimate for the magnetic field strength and the electron
density of the jet plasma.
Description:
3C84 was observed with the GMVA at 86GHz in dual circular polarization
in May 2015. Stokes I, Q and U images of the inner jet of 3C84.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
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03 19 48.16 +41 30 42.1 3C 84 = NGC 1275
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 117 3 List of fits images
fits/* . 3 Individual fits images
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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 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 39 A10 "date" Obs.Date Observation date
41- 47 F7.4 GHz Freq [86.2519] Observed frequency
49- 53 I5 Kibyte size [16394] Size of FITS file
55- 66 A12 --- FileName Name of FITS file, in subdirectory fits
68-117 A50 --- Title Title of the FITS file
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Acknowledgements:
Jae-Young Kim, jykim(at)mpifr-bonn.mpg.de
(End) Jae-Young Kim [MPIfR, Germany], Patricia Vannier [CDS] 28-Nov-2018