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PreprintCC BY 4.0arXiv

Multi-epoch monitoring of the faint northern component in 3C 84 during 2016-2021

  • Kotaro Niinuma
  • Motoki Kino
  • Nozomu Kawakatsu
  • Hiroshi Nagai
  • Gabriele Giovannini
  • Filippo D'Ammando
  • Monica Orienti
  • Kazuhiro Hada
  • Kiyoaki Wajima
  • Marcello Giroletti
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Abstract

We present the results of multi-epoch very long baseline interferometry (VLBI) observations of the sub-parsec-scale northern jet component of 3C 84 (known as the N1 component) at 7 mm from 2016 to 2021. The peak position of the N1 component exhibits positional variations of approximately 0.2 mas at a distance of about 2.5 mas from the central radio core (C1) throughout the observation period. Although a linear fit yields a small proper motion of μDec=0.054±0.019 mas yr−1, corresponding to an apparent velocity of βapp=0.062±0.021, this displacement is comparable to the observed positional scatter, and the hypothesis that N1 exhibits systematic motion is not statistically supported. In contrast, the peak flux density varies by approximately a factor of two on timescales of several months. We propose two possible explanations for the observed behavior of N1. One is that N1 is the counterpart of the southern hotspot C3, but its motion has been halted by a collision with a compact and dense cloud along its path; in this case, the flux variability may be caused by changes in the free-free absorption opacity of the non-uniform cloud. The other possibility is that N1 is part of the northern jet that is heavily obscured by foreground free-free absorption and is observed through a gap in the absorbing medium; in this case, the variability may reflect intrinsic changes in the jet and its interaction with a non-uniform ambient medium. These results provide new constraints on the physical origin of N1 and on the circumnuclear environment of 3C 84.

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Cite

BibTeXRIS
BibTeX
@misc{niinuma2026multiepoch,
  title = {{Multi-epoch monitoring of the faint northern component in 3C 84 during 2016-2021}},
  author = {Kotaro Niinuma and Motoki Kino and Nozomu Kawakatsu and Hiroshi Nagai and Gabriele Giovannini and Filippo D'Ammando and Monica Orienti and Kazuhiro Hada and Kiyoaki Wajima and Marcello Giroletti},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.07782},
  eprint = {2611.07782},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.07782},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Multi-epoch monitoring of the faint northern component in 3C 84 during 2016-2021
AU  - Kotaro Niinuma
AU  - Motoki Kino
AU  - Nozomu Kawakatsu
AU  - Hiroshi Nagai
AU  - Gabriele Giovannini
AU  - Filippo D'Ammando
AU  - Monica Orienti
AU  - Kazuhiro Hada
AU  - Kiyoaki Wajima
AU  - Marcello Giroletti
PY  - 2026
DA  - 2026/11/05
PB  - arXiv
DO  - 10.48550/arxiv.2611.07782
UR  - https://arxiv.org/abs/2611.07782
AB  - We present the results of multi-epoch very long baseline interferometry (VLBI) observations of the sub-parsec-scale northern jet component of 3C 84 (known as the N1 component) at 7 mm from 2016 to 2021. The peak position of the N1 component exhibits positional variations of approximately 0.2 mas at a distance of about 2.5 mas from the central radio core (C1) throughout the observation period. Although a linear fit yields a small proper motion of μ_Dec=0.054±0.019 mas yr^−1, corresponding to an apparent velocity of β_app=0.062±0.021, this displacement is comparable to the observed positional scatter, and the hypothesis that N1 exhibits systematic motion is not statistically supported. In contrast, the peak flux density varies by approximately a factor of two on timescales of several months. We propose two possible explanations for the observed behavior of N1. One is that N1 is the counterpart of the southern hotspot C3, but its motion has been halted by a collision with a compact and dense cloud along its path; in this case, the flux variability may be caused by changes in the free-free absorption opacity of the non-uniform cloud. The other possibility is that N1 is part of the northern jet that is heavily obscured by foreground free-free absorption and is observed through a gap in the absorbing medium; in this case, the variability may reflect intrinsic changes in the jet and its interaction with a non-uniform ambient medium. These results provide new constraints on the physical origin of N1 and on the circumnuclear environment of 3C 84.
ER  -