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Astronomical Observatory of the Jagiellonian University


Astronomy Object of the Month: 2018, October

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SBS B1646+499: black hole with a jumbled past

Blazars constitute a particular class of so-called active galaxies (AGNs, Active Galactic Nuclei). These exotic objects emit huge amount of energy. Blazars host very masive black holes in their centers, surrounded by accretion discs and toruses. Their high-energy radiation is mostly emitted in collimated streams called jets. The emission of such objects is dominated by the relativistically boosted, non-thermal emission of the jets observed at a small angle to the observer on Earth. In the case of blazar SBS B1646+499, the galaxy activity phase associated with the jet production has already occurred at least twice.

Illustration 1: Spectral index maps for SBS B1646+499 (left panel: giant lobes, right panel: inner radio structure) between 610 MHz GMRT and the VLA 1.5 GHz observations, superimposed on the 610 MHz GMRT intensity contours. Credit: the Authors.

Blazar SBS B1646+499 is situated in the northern sky, in the distance over half a billion light-years from the Earth, making it one of the the closest sources of this type. Thanks to the observations carried out using the Indian radio interferometer Giant Meterwave Radiotelescope (GMRT) at the frequency 610 MHz, the extended radio emission was detected (see the attached map - Illustration 1). The morphology of this blazar resembles a typical radio galaxy, with a visible radio center, a one-sided radio jet and two huge radio lobes extending over a distance of up to ¾ of our distance to the Andromeda Galaxy!

Blazars are objects with the jet directed towards the Earth, thus explaining the double-lobed morphology of this source is not easy. If we can observe the lobes, we should rather expect they are generated by a pair of the opposite oriented jets perpendicular to our line of sight. However, the authors of the presented publication believe that the galaxy - and thus the black hole residing in its center - most likely underwent at least two phases of the nuclear activity in the past, and the observed extended radio emission is the remnant of the first (earlier) phase.

The jet had to change the direction of its propagation, and the reason for this could be so-called Lense-Thirring effect, associated with the precession of a massive rotating body with a high moment of inertia and due to the frame-dragging of the inertial system in strong gravitational field. This mechanism is described and explained on the ground of the General Theory of Relativity.

The authors hope to discover more objects with such turbulent past. They should significantly contribute to a better understanding of the so-called feedback processes occurring in galaxies and galaxy clusters. For example, reoriented jets may be more efficient in heating their gas surroundings.

Original publication: U. Pajdosz-Śmierciak, M. Jamrozy, M. Soida, Ł. Stawarz, Megaparsec-scale Radio Structure Associated with a Hybrid Blazar SBS B1646+499: Episodic Jet Activity with Precessing Axis, accepted by Astrophysical Journal.

The project is part of research conducted at the Departments of Radioastronomy and Space Physics, Stellar and Extragalactic Astronomy, and High Energy Astrophysics of the Jagiellonian University’s Astronomical Observatory (OAUJ).

Urszula Pajdosz-Śmierciak
Astronomical Observatory
Jagiellonian University
Urszula.Pajdosz [at] uj.edu.pl