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25th of July 2022
Re-collimation of the kiloparsec-scale radio jets in NGC 2663
by Velović et al.
How do the jets of plasma ejected from the core of an active galaxy interact with their cosmic environment? As the initially over-pressured jet streams away from the centre of the galaxy, its pressure decreases with distance from the jet base. Eventually it reaches the critical point where the jet pressure falls below the pressure of the external environment. The pressure mismatch can drive an oscillation in the width of the jet, causing it to narrow and brighten with a characteristic length scale. This phenomenon is called recollimation.

Velović et al. present the discovery of highly-collimated radio jets spanning a total of 355 kpc around the nearby elliptical galaxy NGC 2663, and the possible first detection of recollimation on kiloparsec scales. The small distance to the galaxy (∼28.5 Mpc) allows us to resolve portions of the jets to examine their structure. We combine multiwavelength data: radio observations by the Murchison Widefield Array (MWA), the Australian Square Kilometre Array Pathfinder (ASKAP) and the Australia Telescope Compact Array (ATCA), and X-ray data from several satellite missions. Regions of the southern jet show simultaneous narrowing and brightening, which can be interpreted as a signature of the recollimation of the jet by external, environmental pressure, though it is also consistent with an intermittent Active Galactic Nuclei (AGN) or complex internal jet structure. The image above shows images of NGC 2663 at 200 MHz from the MWA on the left, and at 1520 MHz from ASKAP on the right, showing potential recollimation knots in the southern jet. The paper will be published in the Monthly Notices of the Royal Astronomical Society.

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