2019A&A...623A.111H


Query : 2019A&A...623A.111H

2019A&A...623A.111H - Astronomy and Astrophysics, volume 623A, 111-111 (2019/3-1)

Magnetic field at a jet base: extreme Faraday rotation in 3C 273 revealed by ALMA.

HOVATTA T., O'SULLIVAN S., MARTI-VIDAL I., SAVOLAINEN T. and TCHEKHOVSKOY A.

Abstract (from CDS):


Aims. We studied the polarization behavior of the quasar 3C 273 over the 1 mm wavelength band at ALMA with a total bandwidth of 7.5GHz across 223-243GHz at 0.8'' resolution, corresponding to 2.1kpc at the distance of 3C 273. With these observations we were able to probe the optically thin polarized emission close to the jet base, and constrain the magnetic field structure.
Methods. We computed the Faraday rotation measure using simple linear fitting and Faraday rotation measure synthesis. In addition, we modeled the broadband behavior of the fractional Stokes Q and U parameters (qu-fitting). The systematic uncertainties in the polarization observations at ALMA were assessed through Monte Carlo simulations.
Results. We find the unresolved core of 3C 273 to be 1.8% linearly polarized. We detect a very high rotation measure (RM) of (5.0±0.3)x105rad/m2 over the 1 mm band when assuming a single polarized component and an external RM screen. This results in a rotation of >40° of the intrinsic electric vector position angle, which is significantly higher than typically assumed for millimeter wavelengths. The polarization fraction increases as a function of wavelength, which according to our qu-fitting could be due to multiple polarized components of different Faraday depth within our beam or to internal Faraday rotation. With our limited wavelength coverage we cannot distinguish between the cases, and additional multifrequency and high angular resolution observations are needed to determine the location and structure of the magnetic field of the Faraday active region. Comparing our RM estimate with values obtained at lower frequencies, the RM increases as a function of observing frequency, following a power law with an index of 2.0±0.2, consistent with a sheath surrounding a conically expanding jet. We also detect ∼0.2% circular polarization, although further observations are needed to confirm this result.

Abstract Copyright: © ESO 2019

Journal keyword(s): polarization - quasars: individual: 3C 273 - galaxies: jets - radio continuum: galaxies

VizieR on-line data: <Available at CDS (J/A+A/623/A111): table1.dat>

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 3C 84 Sy2 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 3793 3
2 M 81 Sy2 09 55 33.1726556496 +69 03 55.062505368   7.89 6.94     ~ 4201 3
3 4C 03.23 QSO 12 24 52.4220395184 +03 30 50.290267176   19.02 18.77 18.9   ~ 133 1
4 M 84 Sy2 12 25 03.74333 +12 53 13.1393 12.67 12.09 10.49     ~ 1703 2
5 3C 273 BLL 12 29 06.6998257176 +02 03 08.597629980   13.05 14.830 14.11   ~ 5584 1
6 M 87 BiC 12 30 49.42338230 +12 23 28.0438581 10.16 9.59 8.63   7.49 ~ 6705 3
7 3C 279 Bla 12 56 11.1663795384 -05 47 21.528432492   18.01 17.75 15.87   ~ 2889 2

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2022.08.15-15:03:58

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