MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales

D. I. Zobnina; H. D. Aller; M. F. Aller; D. C. Homan; Y. Y. Kovalev; M. L. Lister; I. N. Pashchenko; A. B. Pushkarev; T. Savolainen

doi:10.1093/mnras/stad1481

MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales

D. I. Zobnina^*
, H. D. Aller
, M. F. Aller
, D. C. Homan
, Y. Y. Kovalev
, M. L. Lister
, I. N. Pashchenko
, A. B. Pushkarev
, T. Savolainen

^*Corresponding author for this work

Research output: Contribution to journal › Article › Scientific › peer-review

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Abstract

Using stacking of images obtained at different epochs, we studied the variability properties of linear polarization of active galactic nucleus (AGN) jets on parsec-scales. Our sample is drawn from the MOJAVE programme, and consists of 436 AGNs manifesting core-jet morphology and having at least five VLBA observing epochs at 15 GHz from 1996 January through 2019 August, with some additional archival VLBA data reduced by us. We employed a stacking procedure and constructed maps of (i) standard deviation of fractional polarization and electric vector position angle (EVPA) over epochs as the measure of variability and (ii) median polarization degree to quantify typical values in time. The distributions of these values along and across the jet were analysed for the whole sample for the first time. We found that core EVPA variability is typically higher than that of the jet, presumably due to component blending and outflow bends in the core. The BL Lacertae object cores have lower EVPA variability, compared to that of quasars, possibly due to lower Faraday rotation measure, suggesting a stronger ordered magnetic field component. The EVPA becomes more stable down the jet. Most of the sources showing this trend have a time coverage of more than 12 yr and at least 15 epochs. The possible cause could be the increase of stability in the magnetic field direction, reflecting an increase in the fraction of the magnetic field that is ordered. There are no significant optical-class-dependent or spectral-class-dependent relations in the EVPA variability properties in AGN jets.

Original language	English
Pages (from-to)	3615-3628
Number of pages	14
Journal	Monthly Notices of the Royal Astronomical Society
Volume	523
Issue number	3
DOIs	https://doi.org/10.1093/mnras/stad1481
Publication status	Published - 1 Aug 2023
MoE publication type	A1 Journal article-refereed

Funding

We thank the anonymous referee for helpful suggestions on the manuscript, the members of the MOJAVE team for discussions of the paper, Eduardo Ros for valuable comments on the manuscript as well as Elena Bazanova for language editing. The analysis presented in this paper was supported by the Russian Foundation for Basic Research grant 20–32–90108. The estimation of the uncertainties presented in the Appendix was supported by the Russian Science Foundation grant 21–12–00241. The MOJAVE project was supported by NASA–Fermi grants NNX08AV67G,NNX12A087G, and NNX15AU76G. This work is part of the M2FINDERS project which has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No 101018682). This research made use of the data from the University of Michigan Radio Astronomy Observatory (UMRAO), which was supported by the University of Michigan and by a series of grants from the National Science Foundation, most recently No. AST–0607523 and by a series of grants from the NASA Fermi G.I. Program. This research made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The Long Baseline Observatory and the National Radio Astronomy Observatory are facilities of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator (Deller et al. ) developed as part of the Australian Major National Research Facilities Programme and operated under licence.

Keywords

BL Lacertae objects: general
galaxies: active
galaxies: jets
polarization
quasars: general
radio continuum: galaxies

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10.1093/mnras/stad1481

Zobnina_MojaveFinal published version, 2.89 MB

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@article{7db39a5219d54dd3b9857f6d246bed2c,

title = "MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales",

abstract = "Using stacking of images obtained at different epochs, we studied the variability properties of linear polarization of active galactic nucleus (AGN) jets on parsec-scales. Our sample is drawn from the MOJAVE programme, and consists of 436 AGNs manifesting core-jet morphology and having at least five VLBA observing epochs at 15 GHz from 1996 January through 2019 August, with some additional archival VLBA data reduced by us. We employed a stacking procedure and constructed maps of (i) standard deviation of fractional polarization and electric vector position angle (EVPA) over epochs as the measure of variability and (ii) median polarization degree to quantify typical values in time. The distributions of these values along and across the jet were analysed for the whole sample for the first time. We found that core EVPA variability is typically higher than that of the jet, presumably due to component blending and outflow bends in the core. The BL Lacertae object cores have lower EVPA variability, compared to that of quasars, possibly due to lower Faraday rotation measure, suggesting a stronger ordered magnetic field component. The EVPA becomes more stable down the jet. Most of the sources showing this trend have a time coverage of more than 12 yr and at least 15 epochs. The possible cause could be the increase of stability in the magnetic field direction, reflecting an increase in the fraction of the magnetic field that is ordered. There are no significant optical-class-dependent or spectral-class-dependent relations in the EVPA variability properties in AGN jets.",

keywords = "BL Lacertae objects: general, galaxies: active, galaxies: jets, polarization, quasars: general, radio continuum: galaxies",

author = "Zobnina, \{D. I.\} and Aller, \{H. D.\} and Aller, \{M. F.\} and Homan, \{D. C.\} and Kovalev, \{Y. Y.\} and Lister, \{M. L.\} and Pashchenko, \{I. N.\} and Pushkarev, \{A. B.\} and T. Savolainen",

note = "Funding Information: We thank the anonymous referee for helpful suggestions on the manuscript, the members of the MOJAVE team for discussions of the paper, Eduardo Ros for valuable comments on the manuscript as well as Elena Bazanova for language editing. The analysis presented in this paper was supported by the Russian Foundation for Basic Research grant 20–32–90108. The estimation of the uncertainties presented in the Appendix was supported by the Russian Science Foundation grant 21–12–00241. The MOJAVE project was supported by NASA–Fermi grants NNX08AV67G,NNX12A087G, and NNX15AU76G. This work is part of the M2FINDERS project which has received funding from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 Research and Innovation Programme (grant agreement No 101018682). This research made use of the data from the University of Michigan Radio Astronomy Observatory (UMRAO), which was supported by the University of Michigan and by a series of grants from the National Science Foundation, most recently No. AST–0607523 and by a series of grants from the NASA Fermi G.I. Program. This research made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The Long Baseline Observatory and the National Radio Astronomy Observatory are facilities of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator (Deller et al. ) developed as part of the Australian Major National Research Facilities Programme and operated under licence. Publisher Copyright: {\textcopyright} 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.",

year = "2023",

month = aug,

day = "1",

doi = "10.1093/mnras/stad1481",

language = "English",

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pages = "3615--3628",

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T1 - MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales

AU - Zobnina, D. I.

AU - Aller, H. D.

AU - Aller, M. F.

AU - Homan, D. C.

AU - Kovalev, Y. Y.

AU - Lister, M. L.

AU - Pashchenko, I. N.

AU - Pushkarev, A. B.

AU - Savolainen, T.

N1 - Funding Information: We thank the anonymous referee for helpful suggestions on the manuscript, the members of the MOJAVE team for discussions of the paper, Eduardo Ros for valuable comments on the manuscript as well as Elena Bazanova for language editing. The analysis presented in this paper was supported by the Russian Foundation for Basic Research grant 20–32–90108. The estimation of the uncertainties presented in the Appendix was supported by the Russian Science Foundation grant 21–12–00241. The MOJAVE project was supported by NASA–Fermi grants NNX08AV67G,NNX12A087G, and NNX15AU76G. This work is part of the M2FINDERS project which has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No 101018682). This research made use of the data from the University of Michigan Radio Astronomy Observatory (UMRAO), which was supported by the University of Michigan and by a series of grants from the National Science Foundation, most recently No. AST–0607523 and by a series of grants from the NASA Fermi G.I. Program. This research made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The Long Baseline Observatory and the National Radio Astronomy Observatory are facilities of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator (Deller et al. ) developed as part of the Australian Major National Research Facilities Programme and operated under licence. Publisher Copyright: © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

PY - 2023/8/1

Y1 - 2023/8/1

N2 - Using stacking of images obtained at different epochs, we studied the variability properties of linear polarization of active galactic nucleus (AGN) jets on parsec-scales. Our sample is drawn from the MOJAVE programme, and consists of 436 AGNs manifesting core-jet morphology and having at least five VLBA observing epochs at 15 GHz from 1996 January through 2019 August, with some additional archival VLBA data reduced by us. We employed a stacking procedure and constructed maps of (i) standard deviation of fractional polarization and electric vector position angle (EVPA) over epochs as the measure of variability and (ii) median polarization degree to quantify typical values in time. The distributions of these values along and across the jet were analysed for the whole sample for the first time. We found that core EVPA variability is typically higher than that of the jet, presumably due to component blending and outflow bends in the core. The BL Lacertae object cores have lower EVPA variability, compared to that of quasars, possibly due to lower Faraday rotation measure, suggesting a stronger ordered magnetic field component. The EVPA becomes more stable down the jet. Most of the sources showing this trend have a time coverage of more than 12 yr and at least 15 epochs. The possible cause could be the increase of stability in the magnetic field direction, reflecting an increase in the fraction of the magnetic field that is ordered. There are no significant optical-class-dependent or spectral-class-dependent relations in the EVPA variability properties in AGN jets.

AB - Using stacking of images obtained at different epochs, we studied the variability properties of linear polarization of active galactic nucleus (AGN) jets on parsec-scales. Our sample is drawn from the MOJAVE programme, and consists of 436 AGNs manifesting core-jet morphology and having at least five VLBA observing epochs at 15 GHz from 1996 January through 2019 August, with some additional archival VLBA data reduced by us. We employed a stacking procedure and constructed maps of (i) standard deviation of fractional polarization and electric vector position angle (EVPA) over epochs as the measure of variability and (ii) median polarization degree to quantify typical values in time. The distributions of these values along and across the jet were analysed for the whole sample for the first time. We found that core EVPA variability is typically higher than that of the jet, presumably due to component blending and outflow bends in the core. The BL Lacertae object cores have lower EVPA variability, compared to that of quasars, possibly due to lower Faraday rotation measure, suggesting a stronger ordered magnetic field component. The EVPA becomes more stable down the jet. Most of the sources showing this trend have a time coverage of more than 12 yr and at least 15 epochs. The possible cause could be the increase of stability in the magnetic field direction, reflecting an increase in the fraction of the magnetic field that is ordered. There are no significant optical-class-dependent or spectral-class-dependent relations in the EVPA variability properties in AGN jets.

KW - BL Lacertae objects: general

KW - galaxies: active

KW - galaxies: jets

KW - polarization

KW - quasars: general

KW - radio continuum: galaxies

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U2 - 10.1093/mnras/stad1481

DO - 10.1093/mnras/stad1481

M3 - Article

AN - SCOPUS:85162209789

SN - 0035-8711

VL - 523

SP - 3615

EP - 3628

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

ER -

MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales

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MOJAVE - XXI. Decade-long linear polarization variability in AGN jets at parsec scales

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