A1 Refereed original research article in a scientific journal
Investigating Differences in the Palomar-Green Blazar Population Using Polarization
Authors: Baghel, Janhavi; Kharb, P.; Hovatta, T.; Ho, Luis C.; Harrison, C.; Lindfors, E.; Silpa, S.; Gulati, S.
Publisher: IOP Publishing Ltd
Publishing place: BRISTOL
Publication year: 2024
Journal: Astrophysical Journal
Journal name in source: ASTROPHYSICAL JOURNAL
Journal acronym: ASTROPHYS J
Article number: 192
Volume: 977
Issue: 2
Number of pages: 23
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ad8d58
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ad8d58
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/478109053
We present polarization images with the Karl G. Jansky Very Large Array (VLA) in A- and B-array configurations at 6 GHz of seven radio-loud (RL) quasars and eight BL Lac objects belonging to the Palomar-Green (PG) "blazar" sample. This completes our arcsecond-scale polarization study of an optically selected volume-limited blazar sample comprising 16 radio-loud quasars and 8 BL Lac objects. Using the VLA, we identify kiloparsec-scale polarization in the cores and jets/lobes of all the blazars, with fractional polarization varying from around 0.8% +/- 0.3% to 37% +/- 6%. The kiloparsec-scale jets in PG RL quasars are typically aligned along their parsec-scale jets and show apparent magnetic fields parallel to jet directions in their jets/cores and magnetic field compression in their hot spots. The quasars show evidence of interaction with their environment as well as restarted active galactic nucleus activity through morphology, polarization, and spectral indices. These quasi-periodic jet modulations and restarted activity may be indicative of an unstable accretion disk undergoing transition. We find that the polarization characteristics of the BL Lacs are consistent with their jets being reoriented multiple times, with no correlation between their core apparent magnetic field orientations and parsec-scale jet directions. We find that the low synchrotron peaked BL Lacs show polarization and radio morphology features typical of "strong" jet sources as defined by E. T. Meyer et al. for the "blazar envelope scenario," which posits a division based on jet profiles and velocity gradients rather than total jet power.
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Funding information in the publication:
Department of Atomic Energy, Government of India, under the project 12-R&D-TFR-5.02-0700. L.C.H. was supported by the National Science Foundation of China (11991052, 12233001), the National Key R&D Program of China (2022YFF0503401), and the China Manned Space Project (CMS-CSST-2021-A04, CMS-CSST-2021-A06). C.M.H. acknowledges funding from a United Kingdom Research and Innovation grant (code: MR/V022830/1). S.S. acknowledges financial support from Millennium Nucleus NCN23\_002 (TITANs) and Comité Mixto ESO-Chile. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research has 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.
