Stephan’s Quintet (SQ) is a tightly packed galaxy group located 94 Mpc away, showcasing complex interactions due to ongoing collisions. This study, led by M. I. Arnaudova, leverages cutting-edge observations from the William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) to examine the dynamics and effects of a large-scale shock front (LSSF) formed from these interactions. The study integrates data across wavelengths, including optical, infrared, and radio observations, to understand the role of this shock in shaping the intergalactic medium (IGM).

Observations and Data

The WEAVE instrument provided high-resolution optical spectroscopy across the Quintet, complemented by archival radio observations and James Webb Space Telescope (JWST) infrared data. The shock region's intricate properties, such as velocity, temperature, and density, were studied in unprecedented detail using these datasets.

Findings on the Shock Front

The LSSF, a 45 kpc structure, is a result of NGC 7318b colliding with the group’s IGM at hypersonic speeds. The shock propagates through a medium with multiple gas phases, producing unique emission features. While it is weak in generating relativistic particles needed for radio synchrotron emissions, the shock causes significant adiabatic compression, boosting radio luminosity. Molecular hydrogen detected in the region suggests that some dust survived the collision, allowing gas cooling and recombination.

Multi-phase Gas and Dust Interactions

The study revealed the coexistence of hot plasma, warm molecular gas, and remnants of cooler dust, each contributing to the IGM's energy dissipation. JWST data highlighted PAH and H₂ emissions in areas corresponding to the shock front. Regions of high extinction (dust presence) align with dense gas clumps, suggesting localized shielding against shock destruction.

Implications for Galaxy Interactions

SQ serves as a natural laboratory for understanding how galactic collisions influence star formation and the interstellar medium. The shock-induced heating and compression may trigger bursts of star formation in dense regions while destroying molecular structures in others.

Conclusions

By combining WEAVE’s detailed spectroscopy with multi-wavelength data, the team has provided a nuanced view of the shock’s role in energy redistribution and the lifecycle of gas and dust in SQ. The findings emphasize the complexity of galactic interactions and their long-term impacts on the evolution of galaxies. Future high-resolution studies could further unravel the interplay between shocks, star formation, and the fate of interstellar matter in such dynamic systems.

Source: Arnaudova