The Event Horizon Telescope Image of the Quasar NRAO 530

TL;DR

This paper presents the first high-resolution images of the distant quasar NRAO 530 using the Event Horizon Telescope, revealing detailed jet structure and magnetic field configurations at 230 GHz.

Contribution

The study provides the first 230 GHz images of NRAO 530, showing its jet structure and magnetic field polarization, advancing understanding of quasar jet physics at unprecedented resolution.

Findings

Detected a bright core feature with linear polarization.

Revealed a jet extending over 60 microarcseconds with magnetic field structure.

Identified polarization patterns consistent with a helical magnetic field.

Abstract

We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z=0.902 this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of $\sim$ 20 $\mu$as, both in total intensity and in linear polarization. We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of $\sim$5-8% and has a sub-structure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 $\mu$as along a position angle PA$\sim -$28$^\circ$. It includes two features with orthogonal directions of polarization (electric vector position angle, EVPA), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of linear polarization, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on ${\mu}$as scales, while simultaneous multi-wavelength monitoring will provide insight into the high energy emission origin.