J/A+A/648/A82 Quasar 3C 345 at 18 cm with RadioAstron (Poetzl+, 2021)
Probing the innermost regions of AGN jets and their magnetic fields with
RadioAstron.
IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness
temperature.
Poetzl F.M., Lobanov A.P., Ros E., Gomez J.L., Bruni G., Bach U.,
Fuentes A., Gurvits L.I., Jauncey D.L., Kovalev Y.Y., Kravchenko E.V.,
Lisakov M.M., Savolainen T., Sokolovsky K.V., Zensus J.A.
<Astron. Astrophys. 648, A82 (2021)>
=2021A&A...648A..82P 2021A&A...648A..82P (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Radio sources
Keywords: radio continuum: galaxies - galaxies: active - galaxies: jets -
galaxies: magnetic fields - quasars: individual: 3C 345
Abstract:
Supermassive black holes in the centres of radio-loud active galactic
nuclei (AGN) can produce collimated relativistic outflows (jets).
Magnetic fields are thought to play a key role in the formation and
collimation of these jets, but the details are much debated.
We study the innermost jet morphology and magnetic field strength in
the AGN 3C 345 with an unprecedented resolution using images obtained
within the framework of the key science programme on AGN polarisation
of the Space VLBI mission RadioAstron.
We observed the flat spectrum radio quasar 3C 345 at 1.6GHz on 2016
March 30 with RadioAstron and 18 ground-based radio telescopes in full
polarisation mode.
Our images, in both total intensity and linear polarisation, reveal a
complex jet structure at 300µas as angular resolution,
corresponding to a projected linear scale of about 2pc or a few
thousand gravitational radii. We identify the synchrotron
self-absorbed core at the jet base and find the brightest feature in
the jet 1.5 mas downstream of the core. Several polarised components
appear in the Space VLBI images that cannot be seen from ground
array-only images. Except for the core, the electric vector position
angles follow the local jet direction, suggesting a magnetic field
perpendicular to the jet. This indicates the presence of plane
perpendicular shocks in these regions. Additionally, we infer a
minimum brightness temperature at the largest uv-distances of
1.1x1012K in the source frame, which is above the inverse Compton
limit and an order of magnitude larger than the equipartition value.
This indicates locally efficient injection or re-acceleration of
particles in the jet to counter the inverse Compton cooling or the
geometry of the jet creates significant changes in the Doppler factor,
which has to be >11 to explain the high brightness temperatures.
Description:
Images of the FSRQ 3C345 at 1.6GHz observed with RadioAstron and at
15GHz observed with the VLBA within the MOJAVE project are provided
in Stokes I, Q and U. Note that the presented images in Stokes Q and U
are not corrected for the absolute EVPA calibration, which has to be
applied using the single-dish EVPA as provided in the paper.
Objects:
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RA (2000) DE Designation(s)
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16 42 58.81 +39 48 37.0 3C 345 = IERS B1641+399
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 166 6 List of fits files
fits/* . 6 Individual fits files
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See also:
J/PAZh/25/893 : Optical outbursts of the blazar 3C 345 (Belokon+, 1999)
J/A+A/604/A111 : 22GHz image of 3C 273 (Bruni+, 2017)
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- 51 E11.6 Hz Freq Observed frequency
53- 57 I5 Kibyte size Size of FITS file
59- 70 A12 --- FileName Name of FITS file, in subdirectory fits
72-166 A95 --- Title Title of the FITS file
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Acknowledgements:
Felix Poetzl, fpoetzl(at)mpifr-bonn.mpg.de
References:
Gomez et al., Paper I 2016ApJ...817...96G 2016ApJ...817...96G
Bruni et al., Paper II 2017A&A...604A.111B 2017A&A...604A.111B, Cat. J/A+A/604/A111
Kravchenko et al., Paper III 2020ApJ...893...68K 2020ApJ...893...68K
(End) Patricia Vannier [CDS] 04-Feb-2021