J/A+A/695/A260 The Faraday rotation of NRAO150 (Livingston+, 2025)
A helical magnetic field in quasar NRAO150 revealed by Faraday rotation.
Livingston J.D., Nikonov A.S., Dzib S.A., Debbrecht L.C., Kovalev Y.Y.,
Lisakov M.M., MacDonald N.R., Paraschos G.F., Roder J., Wielgus M.
<Astron. Astrophys. 695, A260 (2025)>
=2025A&A...695A.260L 2025A&A...695A.260L (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Magnetic fields ; Polarization
Keywords: polarization - galaxies: magnetic fields -
quasars: individual: NRAO 150
Abstract:
Active galactic nuclei (AGN) are some of the most luminous and extreme
environments in the Universe. The central engines of AGN are believed
to be super-massive black-holes (SMBHs) are fed by accretion discs
threaded by magnetic fields within a dense magneto-ionic medium.
We report our findings from polarimetric very-long-baseline
interferometry (VLBI) observations of quasar NRAO 150 taken in October
2022 using a combined network of the Very Long Baseline Array (VLBA)
and Effelsberg 100-m Radio Telescope. These observations comprise the
first co-temporal multi-frequency polarimetric VLBI observations of
NRAO 150 at frequencies above 15GHz.
We used the new VLBI polarization calibration procedure, GPCAL, with
polarization observations of frequencies of 12GHz, 15GHz, 24GHz, and
43GHz of NRAO 150. From these observations, we were able to measure
the Faraday rotation and use it to derive the intrinsic electric
vector position angle (EVPA0) for the source. As a complementary
measurement, we determined the behavior of polarization as a function
of observed frequency.
The polarization from NRAO 150 only comes from the core region, with a
peak polarization intensity occurring at 24GHz. Across the core region
of NRAO 150, we see clear gradients in Faraday rotation and EVPA0
values that are aligned with the direction of the jet curving around
the core region. We find that for the majority of the polarized region
the polarization fraction is greater at higher frequencies, with
intrinsic polarization fractions in the core ~=3%.
The Faraday rotation gradients and circular patterns in EVPA0 offer
strong evidence to support the presence of a helical+toroidal magnetic
field. Furthermore, the presence of low intrinsic polarization
fractions indicate that the polarized emission and, hence, the
helical+toroidal magnetic field, is present within the innermost jet.
Description:
The FITS images are the observed Faraday rotation and intrinsic EVPA,
and the associated errors.
Objects:
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RA (2000) DE Designation(s)
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03 59 29.747 +50 57 50.161 NRAO 150 = QSO J0359+5057
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 144 4 List of fits images
fits/* . 4 Individual fits images
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See also:
J/A+A/566/A26 : Jet models for the quasar NRAO150 (Molina+, 2014)
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- 55 A26 "datime" Obs.date Observation date
57- 60 I4 Kibyte size Size of FITS file
62- 72 A11 --- FileName Name of FITS file, in subdirectory fits
74-144 A71 --- Title Title of the FITS file
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Acknowledgements:
Jack Livingston, jack.david.livingston+academic(at)gmail.com
(End) Patricia Vannier [CDS] 28-Feb-2025