Multifrequency study of a double-double radio galaxy J1706+4340

TL;DR

This study provides a comprehensive multifrequency radio analysis of the double-double radio galaxy J1706+4340, revealing its age, jet activity cycle, and black hole spin influence on jet properties.

Contribution

It offers the first detailed multifrequency radio analysis of J1706+4340, highlighting its dynamical evolution and the role of black hole spin in jet production.

Findings

Outer lobes are 260-300 Myr old.

Jet activity restarted 12 Myr ago after 27 Myr quiescence.

Inner and outer jets have similar spectral indices and powers.

Abstract

We report the outcome of multifrequency radio observations of a double-double radio source J1706+4340 carried out with the Very Large Array and Giant Metrewave Radio Telescope. After supplementing our own data with those available in the literature, we collected a considerable set of radio measurements covering the range from 74 to 8460 MHz. This has enabled us to perform a comprehensive review of physical properties of the source and its dynamical evolution analysis. In particular, we found that, while the age of the large-scale outer lobes is in the range 260-300 Myr, the renewal of the jet activity, which is directly responsible for the double-double structure, took place only about 12 Myr ago after about 27-Myr long period of quiescence. Another important property of J1706+4340 we found is that the injection spectral indices and the jet powers for the inner and the outer doubles are very similar. This implies that it is the spin of the supermassive black hole rather than e.g. an instability of the accretion disc that is likely responsible for the jet production and its properties.