Parsec-scale alignments of radio–optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program
Alignment of radio–optical offsets with AGN jets (Lambert et al. 2021, A&A 651, A64)Abstract
This paper investigates the relative positions of quasar emission centers at multiple wavelengths to link different realizations of the International Celestial Reference System (ICRS) and to reveal systematics and individual behaviors in active galactic nuclei (AGNs). Using the ICRF3 positions at X, K, and Ka bands, Gaia EDR3 optical positions, and MOJAVE jet kinematics for 194 sources, we examined the orientation between radio–optical offsets and the parsec-scale jet directions. The majority of sources exhibit radio-to-optical vectors aligned with their jets, with the optical centroid located downstream from the radio centroids. The K and Ka centroids are generally upstream relative to X, consistent with the core–jet model. Several optical centroids coincide with stationary radio components showing significant polarization, indicating synchrotron-dominated optical emission. These results confirm that multiwavelength astrometry can independently trace jet directions and that the ICRF3 X-band frame is stable and reliable.
This work combines multifrequency VLBI (X, K, Ka bands) and Gaia EDR3 astrometry for 194 AGNs also monitored by MOJAVE to assess the alignment between radio–optical offsets and relativistic jet directions. The authors found that most radio–optical position vectors are aligned with the parsec-scale jets, implying that Gaia optical centroids lie downstream from the radio cores, whereas higher-frequency (K, Ka) centroids are upstream relative to X. Such geometry supports a simple core–jet model. In some cases, optical centroids coincide with stationary polarized radio features, indicating synchrotron-dominated optical emission. The results highlight that astrometric offsets themselves can trace jet orientation without imaging, strengthening the radio–optical tie of the ICRS. :contentReference[oaicite:1]{index=1}
Citation:
Lambert, S., Liu, N., Arias, E. F., Barache, C., Souchay, J., Taris, F., Liu, J.-C., & Zhu, Z. (2021).
Parsec-scale alignments of radio–optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program.
Astronomy & Astrophysics, 651, A64.
https://doi.org/10.1051/0004-6361/202140652