In the cores of distant galaxies, quasars are powerful sources of radiation. Supermassive black holes serve as their primary propulsion systems, accelerating radiation and particles into thin, brilliant jets. Astronomers are trying to understand the complex physics of these cosmic monsters. They need help figuring out exactly how the jets are powered and shaped and what function magnetic fields play in their production.

A global collaboration of scientists used Earth’s virtual radio telescope, the Event Horizon Telescope (EHT), to peer into the heart of a distant quasar NRAO 530. EHT’s extremely high, unprecedented angular resolution allowed astronomers to see previously unseen structures in the central region of NRAO 530.

The EHT collaboration uses a variety of imaging methods to gain certainty about an object’s structure at fine scales that are opaque at longer wavelengths. There are several, including brand new techniques made explicit for high-frequency Very Long Baseline Interferometry (VLBI) imaging, et-imaging, SMILI, DMC, and Themis, as well as the conventional VLBI technique CLEAN.

The image shows images of the quasar NRAO 530 obtained in different ways in total and polarized light. The images reveal a bright feature on the south side of the jet, which the authors associate with the VLBI core at millimeter wavelengths.

The core of quasars such as NRAO 530 manifests as the location where the beam begins at a specific wavelength. The beam extends the distance light travels in ~1.7 years when projected onto the plane of the sky. It contains two features with orthogonal polarization directions (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet.

According to scientists, it indicates a spiral structure of the magnetic field in the jet.

Dr. Svetlana Jorstad, a senior scientist at Boston University, USA, who leads the NRAO 530 project said: “The outer feature has a particularly high degree of linear polarization, indicating a very well-ordered magnetic field.”

Dr. Maciek Wielgus, a scientist at the Max Planck Institute for Radio Astronomy in Bonn, Germany, who co-led this study, said: “It is also the furthest object we have imaged with the EHT to date. The light we see traveled 7.5 billion years to Earth through the expanding universe, but with the power of the EHT we see the details of the source structure on a scale as small as a single light-year.”

The EHT collaboration looks forward to future observations of the quasar to understand how the inner beam characteristics and their connection to high-energy photon production change over time, as NRAO 530 is a known source of powerful gamma rays.

Magazine reference:

  1. S. Jorstad, M. Wielgus, et al. +EHTC: “The Event Horizon Telescope Image of the Quasar NRAO 530,” in Astrophysical Journal ApJ 943 170 (2023). DOI: 10.3847/1538-4357/acaea8