Investigating Differences in the Palomar-Green Blazar Population Using Polarization
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...
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2024-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad8d58 |
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| author | Janhavi Baghel P. Kharb T. Hovatta Luis C. Ho C. Harrison E. Lindfors Silpa S. S. Gulati |
| author_facet | Janhavi Baghel P. Kharb T. Hovatta Luis C. Ho C. Harrison E. Lindfors Silpa S. S. Gulati |
| author_sort | Janhavi Baghel |
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| description | 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. |
| format | Article |
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| language | English |
| publishDate | 2024-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-4b91cf01e8164412b95d9b3de33f2d382025-08-20T01:59:05ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01977219210.3847/1538-4357/ad8d58Investigating Differences in the Palomar-Green Blazar Population Using PolarizationJanhavi Baghel0https://orcid.org/0000-0002-0367-812XP. Kharb1https://orcid.org/0000-0003-3203-1613T. Hovatta2https://orcid.org/0000-0002-2024-8199Luis C. Ho3https://orcid.org/0000-0001-6947-5846C. Harrison4https://orcid.org/0000-0001-8618-4223E. Lindfors5Silpa S.6https://orcid.org/0000-0003-0667-7074S. Gulati7https://orcid.org/0000-0003-3785-1725National Centre for Radio Astrophysics (NCRA)—Tata Institute of Fundamental Research (TIFR), S. P. Pune University Campus , Ganeshkhind, Pune 411007, India ; jbaghel@ncra.tifr.res.inNational Centre for Radio Astrophysics (NCRA)—Tata Institute of Fundamental Research (TIFR), S. P. Pune University Campus , Ganeshkhind, Pune 411007, India ; jbaghel@ncra.tifr.res.inFinnish Centre for Astronomy with ESO, FINCA, University of Turku , Turku, Finland; Aalto University Metsähovi Radio Observatory , Metsähovintie 114, 02540 Kylmälä, FinlandKavli Institute for Astronomy and Astrophysics, Peking University , Beijing 100871, People's Republic of China; Department of Astronomy, School of Physics, Peking University , Beijing 100871, People's Republic of ChinaSchool of Mathematics, Statistics and Physics, Newcastle University , Newcastle upon Tyne NE1 7RU, UKFinnish Centre for Astronomy with ESO, FINCA, University of Turku , Turku, FinlandDepartamento de Astronomìa, Universidad de Concepciòn , Barrio Universitario s/n, Concepciòn, ChileNational Centre for Radio Astrophysics (NCRA)—Tata Institute of Fundamental Research (TIFR), S. P. Pune University Campus , Ganeshkhind, Pune 411007, India ; jbaghel@ncra.tifr.res.inWe 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.https://doi.org/10.3847/1538-4357/ad8d58Active galaxiesBlazarsBL Lacertae objectsQuasarsRadio jetsPolarimetry |
| spellingShingle | Janhavi Baghel P. Kharb T. Hovatta Luis C. Ho C. Harrison E. Lindfors Silpa S. S. Gulati Investigating Differences in the Palomar-Green Blazar Population Using Polarization The Astrophysical Journal Active galaxies Blazars BL Lacertae objects Quasars Radio jets Polarimetry |
| title | Investigating Differences in the Palomar-Green Blazar Population Using Polarization |
| title_full | Investigating Differences in the Palomar-Green Blazar Population Using Polarization |
| title_fullStr | Investigating Differences in the Palomar-Green Blazar Population Using Polarization |
| title_full_unstemmed | Investigating Differences in the Palomar-Green Blazar Population Using Polarization |
| title_short | Investigating Differences in the Palomar-Green Blazar Population Using Polarization |
| title_sort | investigating differences in the palomar green blazar population using polarization |
| topic | Active galaxies Blazars BL Lacertae objects Quasars Radio jets Polarimetry |
| url | https://doi.org/10.3847/1538-4357/ad8d58 |
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