A galactic microquasar mimicking winged radio galaxies

Abstract

A subclass of extragalactic radio sources known as winged radio galaxies has puzzled astronomers for many years. The wing features are detected at radio wavelengths as low-surface-brightness radio lobes that are clearly misaligned with respect to the main lobe axis. Different models compete to account for these peculiar structures. Here, we report observational evidence that the parsec-scale radio jets in the Galactic microquasar GRS 1758-258 give rise to a Z-shaped radio emission strongly reminiscent of the X and Z-shaped morphologies found in winged radio galaxies. This is the first time that such extended emission features are observed in a microquasar, providing a new analogy for its extragalactic relatives. From our observations, we can clearly favour the hydrodynamic backflow interpretation against other possible wing formation scenarios. Assuming that physical processes are similar, we can extrapolate this conclusion and suggest that this mechanism could also be at work in many extragalactic cases.

The content of astrophysical jets

“…Instead, magnetic dominance of the jet creates a "nose cone" â Ȃ Ş a shaped head, which is rarely observed, and might be produced also by some combinations of heavy jets and ambient medium (Komissarov 1999;Komissarov & Falle 2003). Back-flowing cocoons have been recently observed in micro-quasars as well, in accordance with the expected hydrodynamic nature of their jets (Martí et al 2015(Martí et al , 2017.…”

Are jets in GRS 1758-258 precessing?

“…The Z-shaped observed morphology in such cocoon for GRS 1758-258 was intriguing because it seemed to mimic winged radiogalaxies. This new link between microquasars and their extragalactic relatives has been proposed and reported in detail no long ago [15], with some consequences in the black hole merger rate for extragalactic sources and their corresponding gravitational wave production.…”

“…Even taking into account that the donor star lifetime τ * ∼ 2 × 10 10 years [25] could be one order of magnitude less than τ bin , the alignment timescale is of the order of the system life. As, in addition, τ align is greater than the jet travel time τ j 10 5 years [15], the black hole spin axis in GRS 1758-258 could be misaligned with the orbital orbital momentum, as usual in X-ray binaries with black holes [20], giving rise to precession.…”

Propagation and stability of relativistic jets

“…Although microquasar jets may form via the same physical mechanisms as extragalactic jets and may resemble them at large scales [73], the environment through which they evolve is extremely different from that through which extragalactic jets propagate. In the case of young microquasars, the jet may cross the companion wind, shocked wind, the supernova remnant (SNR), and the shocked interstellar medium (ISM), before entering the ISM.…”