Collimation of the kiloparsec-scale radio jets in NGC 2663

Abstract: We 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 Chandra, Swift and SRG/eROSITA. We present intensity, rotation measure, polarisation, spectral index and X-ray environment maps. 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. X-ray data suggest that the environment is extremely poor; if the jet is indeed recollimating, the large recollimation scale (40 kpc) is consistent with a slow jet in a low-density environment.

• The paper demonstrates that radio jets in NGC 2663 extend up to 355 kpc with distinct recollimation features influenced by both intrinsic properties and surrounding pressures.
• The study utilizes multi-wavelength data from MWA, ASKAP, ATCA, and X-ray observatories to construct detailed maps of jet intensity, polarization, and spectral indices.
• The paper reveals that the rarefied environmental conditions around NGC 2663 play a key role in jet collimation, challenging traditional models of jet-IGM interactions.

Collimation of the Kiloparsec-Scale Radio Jets in NGC 2663

The paper examines the radio jets surrounding the elliptical galaxy NGC 2663, particularly focusing on the phenomenon of collimation extending over kiloparsec scales. Notably, it reports the discovery of highly-collimated jets covering a span of 355 kpc around NGC 2663. This study incorporates multi-wavelength data from instruments such as the MWA, ASKAP, and ATCA, alongside X-ray data from several observatories.

Key Findings

1. Jet Structure and Collimation: The study uncovers a powerful discovery regarding the radio jets of NGC 2663. The jets are observed to be highly collimated over large kiloparsec-scale distances. In the southern jet, a feature exhibits narrowing and simultaneous brightening, suggesting potential recollimation by external environmental pressures or inherent jet structure complexities.
2. Environmental Interactions: The X-ray data from missions, such as eROSITA, suggest that NGC 2663 exists in a remarkably rarefied environment, featuring no significant surrounding intergalactic medium or dust, which has critical implications for understanding the dynamics of jet collimation on larger scales.
3. Multi-Wavelength Analysis: The researchers present a comprehensive analysis using multi-wavelength observations to construct intensity, rotation measure, polarisation, spectral index, and X-ray environment maps. This multi-spectrum approach provides a granular view of the jet structure and the galaxy's core region.
4. Spectral Analysis: The spectral index distribution shows varying values across different jet regions, with flatter spectral indexes observed near the core, steepening further out. This provides evidence for varied processes occurring along the jet length, possibly indicating differential energy dissipation or particle acceleration along the jet.

Implications

The implications of understanding such collimation phenomena are broad and significant for both observational astronomy and theoretical astrophysics. The research enriches our understanding of jet dynamics, particle acceleration, and jet interaction with the extragalactic medium. It also poses intriguing questions regarding the role of environmental pressure and intrinsic jet properties in forming these expansive structures.

Future Directions

This study serves as a precursor for further observational campaigns and theoretical modeling of similar systems. Future research could leverage upcoming surveys from projects like EMU to identify additional candidates for recollimation, thus enabling more comprehensive statistical analyses. Continued theoretical work, potentially incorporating simulations, is essential to disentangle the contributions of environmental versus intrinsic factors in jet collimation and stability.

In conclusion, the investigation into the radio jets of NGC 2663 provides crucial insights into the intricacies of large-scale jet dynamics and their interactions with the surrounding environment. This contributes significantly to our broader understanding of AGN feedback mechanisms and their role in the evolution of galaxies.