J/MNRAS/469/4034 Broadband polarisation of radio AGN (O'Sullivan+, 2017)
Broadband, radio spectro-polarimetric study of 100 radiative-mode and
jet-mode AGN.
O'Sullivan S.P., Purcell C.R., Anderson C.S., Farnes J.S., Sun X.H.,
Gaensler B.M.
<Mon. Not. R. Astron. Soc. 469, 4034 (2017)>
=2017MNRAS.469.4034O 2017MNRAS.469.4034O (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Polarization
Keywords: radio continuum: galaxies - galaxies: magnetic fields -
techniques: polarimetric - galaxies: jet - galaxies: active
Abstract:
We present the results from a broadband (1 to 3GHz),
spectro-polarimetry study of the integrated emission from 100
extragalactic radio sources with the ATCA, selected to be highly
linearly polarized at 1.4 GHz. We use a general purpose, polarization
model-fitting procedure that describes the Faraday rotation measure
(RM) and intrinsic polarization structure of up to three distinct
polarized emission regions or 'RM components' of a source. Overall,
37%/52%/11% of sources are best fit by one/two/three RM components.
However, these fractions are dependent on the signal-to-noise ratio
(S/N) in polarization (more RM components more likely at higher S/N).
In general, our analysis shows that sources with high integrated
degrees of polarization at 1.4GHz have low Faraday depolarization,
are typically dominated by a single RM component, have a steep
spectral index, and a high intrinsic degree of polarization. After
classifying our sample into radiative-mode and jet-mode AGN, we find
no significant difference between the Faraday rotation or Faraday
depolarization properties of jet-mode and radiative-mode AGN. However,
there is a statistically significant difference in the intrinsic
degree of polarization between the two types, with the jet-mode
sources having more intrinsically ordered magnetic field structures
than the radiative-mode sources. We also find a preferred
perpendicular orientation of the intrinsic magnetic field structure of
jet-mode AGN with respect to the jet direction, while no clear
preference is found for the radiative-mode sources.
Description:
Linear polarisation data as a function of wavelength-squared for 100
extragalactic radio sources, selected to be highly polarised at
1.4GHz.
The data presented here were obtained using the Australia Telescope
Compact Array (ATCA) over 1.1-3.1GHz (16cm) with 1MHz spectral
resolution between 2014 April 19-28. The integrated emission from each
source, imaged at 10 MHz intervals, is presented below. See Section 2
for details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 88 100 Basic properties of all sources in the sample
tablea1.dat 85 16241 The spectropolarimetric data
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See also:
J/ApJS/45/97 : Extragal. Radio Sources Faraday Rot. (Simard-Normandin+ 1981)
J/ApJ/707/114 : Faraday rotation in Cen A (Feain, 2009)
J/MNRAS/421/3300 : Complex Faraday depth structure of AGN (O'Sullivan+, 2012)
J/ApJ/759/25 : Rotation measures at 1.4GHz toward the LMC (Mao+, 2012)
J/AJ/144/105 : MOJAVE. VIII. Faraday rotation in AGN jets. (Hovatta+, 2012)
J/AJ/149/60 : Modeling Faraday structures. I. 1100-1400 MHz (Sun+, 2015)
J/ApJ/825/59 : A Study of Broadband Faraday Rotation (Anderson+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name (JHHMM+DDMM)
12- 18 F7.3 deg RAdeg Right ascension (J2000)
20- 26 F7.3 deg DEdeg Declination (J2000)
28- 32 F5.2 --- alpha Spectral index
34- 37 I4 mJy I2.1GHz Integrated total intensity at 2.1GHz
39- 43 F5.3 --- z Redshift
45- 49 F5.1 rad/m2 |RRM| Absolute value of the residual rotation measure
51- 54 F4.1 rad/m2 sRMw Polarization-weighted RM dispersion
56- 59 F4.1 rad/m2 DRMw Polarization-weighted RM gradient
61- 64 F4.1 % Mean intrinsic degree of polarization
66- 67 I2 --- S/N Polarization signal-to-noise ratio
69 I1 --- N Number of RM components
71- 75 F5.2 --- beta Polarization spectral index
77- 81 A5 --- Morph Total intensity morphology
83 A1 --- l_l Limit flag on l
84- 86 I3 kpc l Linear size
88 A1 --- Rad/Jet [0/1] Radiatice (0) or jet (1) mode
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name (JHHMM+DDMM)
17- 25 F9.7 m2 lsq [0.001/0.06] Wavelength squared
31- 40 F10.7 --- q Stokes Q/I data (fractional)
46- 55 F10.7 --- u Stokes U/I data (fractional)
60- 70 F11.7 --- e_q ?=-99 Uncertainty in Q/I (fractional)
75- 85 F11.7 --- e_u ?=-99 Uncertainty in U/I (fractional)
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Acknowledgements:
Shane O'Sullivan, shane(at)astro.unam.mx
(End) Shane O'Sullivan [IA-UNAM], Patricia Vannier [CDS] 17-Aug-2017