The dichotomy between radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGN) is thought to be intrinsically related to the radio jet production. This difference may be explained by the presence of a strong magnetic field (B-field) that enhances, or is the cause of, the accretion activity and the jet power. Here, we report the first evidence of an intrinsic difference in the dust polarized emission cores of four RL and five RQ AGN using 89 μm polarization with HAWC+/SOFIA. We find that the thermal polarized emission increases with the nuclear radio-loudness, R=L5GHz/LB and R20=L5GHz/L20μm. The dust emission cores of RL AGN are measured to be polarized, ∼5−11%, while RQ AGN are unpolarized, <1. For RQ AGN, our results are consistent with the observed region being filled with an unmagnetized or highly turbulent, disk and/or expanding outflow at scales of 5−80 pc from the AGN. For RL AGN, the measured 89 μm polarization arises primarily from magnetically aligned dust grains associated with a 5−80 pc-scale dusty structure with a toroidal B-field oriented mostly perpendicular, 65±22∘, to the radio jet orientation. Our results indicate that the size and strength of the B-fields surrounding the AGN are intrinsically related to the strength of the jet power -- the stronger the jet power is, the larger and stronger the toroidal B-field is. The detection of a ≤80 pc-scale ordered toroidal B-field suggests that a) the infalling gas that fuels RL AGN is magnetized, b) there is a magnetohydrodynamic wind that collimates the jet, and/or c) the jet is able to magnetize its surroundings.
BT - The Astrophysical Journal DA - 2023-06 DO - 10.3847/1538-4357/accb96 N2 -The dichotomy between radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGN) is thought to be intrinsically related to the radio jet production. This difference may be explained by the presence of a strong magnetic field (B-field) that enhances, or is the cause of, the accretion activity and the jet power. Here, we report the first evidence of an intrinsic difference in the dust polarized emission cores of four RL and five RQ AGN using 89 μm polarization with HAWC+/SOFIA. We find that the thermal polarized emission increases with the nuclear radio-loudness, R=L5GHz/LB and R20=L5GHz/L20μm. The dust emission cores of RL AGN are measured to be polarized, ∼5−11%, while RQ AGN are unpolarized, <1. For RQ AGN, our results are consistent with the observed region being filled with an unmagnetized or highly turbulent, disk and/or expanding outflow at scales of 5−80 pc from the AGN. For RL AGN, the measured 89 μm polarization arises primarily from magnetically aligned dust grains associated with a 5−80 pc-scale dusty structure with a toroidal B-field oriented mostly perpendicular, 65±22∘, to the radio jet orientation. Our results indicate that the size and strength of the B-fields surrounding the AGN are intrinsically related to the strength of the jet power -- the stronger the jet power is, the larger and stronger the toroidal B-field is. The detection of a ≤80 pc-scale ordered toroidal B-field suggests that a) the infalling gas that fuels RL AGN is magnetized, b) there is a magnetohydrodynamic wind that collimates the jet, and/or c) the jet is able to magnetize its surroundings.
PB - arXiv PY - 2022 EP - 31 T2 - The Astrophysical Journal TI - On the origin of radio-loudness in active galactic nuclei using far-infrared polarimetric observations UR - https://iopscience.iop.org/article/10.3847/1538-4357/accb96 VL - 951 ER -