Broad-band, radio spectro-polarimetric study of 100 radiative-mode and jet-mode AGN

We present the results from a broadband (1 to 3 GHz), 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 1.4 GHz 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.

[1]  M. Haverkorn,et al.  Observed Faraday Effects in Damped Lyα Absorbers and Lyman Limit Systems: The Magnetized Environment of Galactic Building Blocks at Redshift = 2 , 2016, 1609.01623.

[2]  S. Poppi,et al.  MAGNETIC FIELD DISORDER AND FARADAY EFFECTS ON THE POLARIZATION OF EXTRAGALACTIC RADIO SOURCES , 2016, 1607.04914.

[3]  A. Hopkins,et al.  GAMA/WiggleZ: the 1.4 GHz radio luminosity functions of high- and low-excitation radio galaxies and their redshift evolution to z = 0.75 , 2016, 1604.04332.

[4]  C. Anderson,et al.  A STUDY OF BROADBAND FARADAY ROTATION AND POLARIZATION BEHAVIOR OVER 1.3–10 GHz IN 36 DISCRETE RADIO SOURCES , 2016, 1604.01403.

[5]  A. Bonafede,et al.  Evidence for a Toroidal Magnetic-Field Component in 5C4.114 on Kiloparsec Scales , 2015, 1511.08730.

[6]  A. Kraus,et al.  A study of a sample of high rotation measure AGNs through multifrequency single dish observations , 2015, 1510.01136.

[7]  M. Lara-L'opez,et al.  THE MAGNETIC FIELD AND POLARIZATION PROPERTIES OF RADIO GALAXIES IN DIFFERENT ACCRETION STATES , 2015, 1504.06679.

[8]  J. Banfield,et al.  Polarization signatures of unresolved radio sources , 2015, 1504.00017.

[9]  Lisa Harvey-Smith,et al.  Estimating extragalactic Faraday rotation , 2014, 1404.3701.

[10]  Lourdes Verdes-Montenegro,et al.  Advancing Astrophysics with the Square Kilometre Array , 2015 .

[11]  L. Rudnick,et al.  COMPARISON OF ALGORITHMS FOR DETERMINATION OF ROTATION MEASURE AND FARADAY STRUCTURE. I. 1100–1400 MHZ , 2014, 1409.4151.

[12]  B. M. Gaensler,et al.  FARADAY ROTATION FROM MAGNESIUM II ABSORBERS TOWARD POLARIZED BACKGROUND RADIO SOURCES , 2014, 1406.2526.

[13]  J. Stil,et al.  Radio galaxies and their magnetic fields out to z ≤ 3 , 2014, 1404.1638.

[14]  Timothy Heckman,et al.  The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe , 2014, 1403.4620.

[15]  E. Carretti,et al.  A BROADBAND POLARIZATION CATALOG OF EXTRAGALACTIC RADIO SOURCES , 2014, 1403.2391.

[16]  K. Kumazaki,et al.  Properties of Intrinsic Polarization Angle Ambiguities in Faraday Tomography , 2014, 1402.0612.

[17]  Nrao,et al.  Systematic properties of decelerating relativistic jets in low-luminosity radio galaxies , 2013, 1311.1015.

[18]  D. Ryu,et al.  Fisher Analysis on Wide-Band Polarimetry for Probing the Intergalactic Magnetic Field , 2013, 1308.5696.

[19]  C. A. Oxborrow,et al.  Planck 2013 results. XVI. Cosmological parameters , 2013, 1303.5076.

[20]  P. Best,et al.  The relation between morphology, accretion modes and environmental factors in local radio AGN , 2013, 1301.1526.

[21]  R. Laing,et al.  The magnetized medium around the radio galaxy B2 0755+37: an interaction with the intragroup gas , 2012, 1203.4582.

[22]  A. R. Taylor,et al.  Complex Faraday depth structure of active galactic nuclei as revealed by broad‐band radio polarimetry , 2012, 1201.3161.

[23]  T. Heckman,et al.  On the fundamental dichotomy in the local radio-AGN population , 2012, 1201.2397.

[24]  Jeroen M. Stil,et al.  Detection Thresholds and Bias Correction in Polarized Intensity , 2011, Publications of the Astronomical Society of Australia.

[25]  M. Lister,et al.  MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VIII. FARADAY ROTATION IN PARSEC-SCALE AGN JETS , 2012 .

[26]  O. Porth,et al.  SYNCHROTRON RADIATION OF SELF-COLLIMATING RELATIVISTIC MAGNETOHYDRODYNAMIC JETS , 2011, 1105.4258.

[27]  India,et al.  The Australia Telescope Compact Array Broadband Backend (CABB): Description & First Results ⋆ , 2011, 1105.3532.

[28]  J. Stil,et al.  POLARIZED RADIO SOURCES: A STUDY OF LUMINOSITY, REDSHIFT, AND INFRARED COLORS , 2011, 1103.4228.

[29]  Shea Brown,et al.  INTEGRATED POLARIZATION OF SOURCES AT λ ∼ 1 m AND NEW ROTATION MEASURE AMBIGUITIES , 2011, 1103.4149.

[30]  R. Laing,et al.  Ordered magnetic fields around radio galaxies: evidence for interaction with the environment , 2011, 1101.1807.

[31]  J. Stil,et al.  A ROTATION MEASURE IMAGE OF THE SKY , 2009 .

[32]  S. O’Sullivan,et al.  Magnetic field strength and spectral distribution of six parsec-scale active galactic nuclei jets , 2009, 0907.5211.

[33]  O. Lahav,et al.  The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures , 2009, 0903.5451.

[34]  P. Best.  Radio source populations: Results from SDSS , 2009 .

[35]  S. O’Sullivan,et al.  Three-dimensional magnetic field structure of six parsec-scale active galactic nuclei jets , 2008, 0811.4426.

[36]  Nrao,et al.  Structures of the magnetoionic media around the Fanaroff–Riley Class I radio galaxies 3C 31 and Hydra A , 2008, 0809.2411.

[37]  D. Evans,et al.  Hot and cold gas accretion and feedback in radio-loud active galaxies , 2007, astro-ph/0701857.

[38]  E. Wright.  A Cosmology Calculator for the World Wide Web , 2006, astro-ph/0609593.

[39]  M. Giroletti,et al.  Polarimetry of Compact Symmetric Objects , 2005, astro-ph/0702456.

[40]  P. Kharb,et al.  When Less Is More: Are Radio Galaxies below the Fanaroff-Riley Break More Polarized on Parsec Scales? , 2005, astro-ph/0509559.

[41]  K. Institute,et al.  Faraday rotation measure synthesis , 2005, astro-ph/0507349.

[42]  S. Iguchi,et al.  A Helical Magnetic Field in the jet of 3C 273(Session 1:Astrophysical Jets,High-Energy Emission from Accreting Compact Objects,Korea-Japan Seminar) , 2002, astro-ph/0205497.

[43]  S.Cole,et al.  The 2dF Galaxy Redshift Survey: spectra and redshifts , 2001, astro-ph/0106498.

[44]  D. J. Saikia,et al.  A Polarization Study of Radio Galaxies and Quasars selected from the Molonglo Complete Sample , 1998, astro-ph/9811337.

[45]  D. Sokoloff,et al.  Depolarization and Faraday effects in galaxies , 1998 .

[46]  A. Raftery.  Bayesian Model Selection in Social Research , 1995 .

[47]  E. Greisen,et al.  The NRAO VLA Sky Survey , 1996 .

[48]  Peter C. Tribble,et al.  Depolarization of extended radio sources by a foreground Faraday screen , 1991 .

[49]  Simon T. Garrington,et al.  The interpretation of asymmetric depolarization in extragalactic radio sources , 1991 .

[50]  R. Laing.  The sidedness of jets and depolarization in powerful extragalactic radio sources , 1988, Nature.

[51]  J. Leahy,et al.  A systematic asymmetry in the polarization properties of double radio sources with one jet , 1988, Nature.

[52]  D. J. Saikia,et al.  POLARIZATION PROPERTIES OF EXTRAGALACTIC RADIO SOURCES , 1988 .

[53]  J. Leahy.  Small-scale variations in the Galactic Faraday rotation , 1987 .

[54]  T. Heckman,et al.  Optical emission-line gas associated with the radio source 3C 277. 3 , 1985 .

[55]  J. N. Clarke,et al.  Evidence for the magnetic-field orientation in extragalactic radio sources , 1980 .

[56]  J. Wardle,et al.  The Radio Polarisation of Quasars , 1974 .

[57]  J. Gilbert,et al.  The Polarization of Radio Sources with Appreciable Redshift , 1972 .

[58]  J. Whiteoak,et al.  The Polarization of Cosmic Radio Waves , 1966 .

[59]  B. Burn.  On the Depolarization of Discrete Radio Sources by Faraday Dispersion , 1965 .