3C 111 Total intensity image at 5 GHz. Credit: arxiv (2025). DOI: 10.48550 / Arxiv.2503.18621
Using the very long basic table (VLBA), European astronomers have made radio observations with several wavelengths of a Galaxy radio designated 3C 111. Results of the observation campaign, published on March 24 on the arxiv Pre -print server, throws more light on the properties of this galaxy and its relativistic jet.
Radio-galaxies (RGS) emit enormous amounts of radio waves from their central nuclei. Black holes in the centers of these galaxies accre the gas and dust, generating high energy jets visible in the radio wavelengths, which accelerate the electrically loaded particles at high speeds.
Based on their morphology and their radio brightness, astronomers divide radio-galaxies into RG FR I and FR II. FR I radio-galaxies have lower power and their emission is dominated by their jet; On the other hand, those of the FR II class have high power and are dominated on a large scale by hot spots, that is to say regions in which a jet ends due to an interaction with the intergalactic environment.
Located at around 640 million light years, 3C 111 is a RG with a typical morphology of the FR II. It presents radio lobes, a strong nucleus and a prominent unilateral jet, ending in the hot spot of the northeast lobe. The jet has a Blazar -shaped behavior, showing an apparent superluminal movement.
A team of astronomers led by Vieri Bartolini of the Max Planck Institute for Radio Astronomy in Bonn, Germany, decided to take a look at 3C 111, focusing on its radio programs and its jet properties.
“In this article, we present a set of high frequency and high frequency radio emissions of radio emissions at PC scale in radio-win-line 3C 111. The images are obtained in full polarization with the VLBA, and as such, our work is the first study of this jet with simultaneous data of 5 GHz up to 87.6 GHz,” explained the researchers.
The 3C 111 was detected by the Bartolini team at all the frequencies used. The images obtained seem to be dominated by a compact nucleus of brightness going between 3.0 JY and 1.0 dy (at 8.4 GHz and 87.6 GHz, respectively).
The observations revealed that a unilateral jet emerges from the nucleus of 3C 111. The jet is remarkably right, oriented at a position angle of approximately 65 degrees and shows little or no proof of flexion on its full extension.
According to the study, the spectral index for the nucleus of 3C 111 varies from 1.5 in the pair of lower frequencies 5−8.4 GHz to approximately 0 in the higher frequency pair 43.8 –87.6 GHz. The spectral index along the jet has generally proven to be stiff, reaching a minimum value of approximately -3.0 in the highest pair of frequencies.
In addition, the distribution of the brightness temperature across 3C 111 varies from 10 million to around 1 Billion from K. The magnetic field of the equipment was estimated at the order of 1 to 100 mg through the radio-winner.
Observations also revealed that the polarized emission is mainly in the jet at all frequencies, and with an increasing frequency, this emission also comes from regions gradually closer to the jet base.
More information:
V. Bartolini et al, Simultaneous VLBA view of the Radio 111 source, arxiv (2025). DOI: 10.48550 / Arxiv.2503.18621
Newspaper information:
arxiv
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