Active black holes reveal star-forming rings and shock waves in nine nearby galaxies

A new study of nine nearby galaxies has revealed that actively growing supermassive black holes may contribute to, rather than prevent, star formation. The research, based on observations from the VLT/MUSE instrument, shows that active galactic nuclei (AGN) are associated with star-forming rings or arcs, cone-shaped regions of energized gas, and fast "shocks," which occur when energy outflows interact with surrounding gas. The findings, published in The Astrophysical Journal, give a new perspective on how AGN feedback could influence the growth and evolution of galaxies. The study focused on galaxies whose central black holes are actively accreting, or pulling in, nearby material. "We're seeing that black holes are not just consuming material at the centers of galaxies, but they're actively reshaping their surroundings," said Lisa Kewley, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, director of the center and Zhu's adviser. The researchers found that star-forming rings or arcs appeared at distances of about 0.8 to 6 kiloparsecs from the galactic center. Ionized cones of black-hole radiation extended outward from the galaxies' disks, while central regions dominated by fast shocks often extended perpendicular to those bicones. The study's results combined high-resolution observations and detailed theoretical models. The MUSE instrument provided spatially resolved optical data, while the state-of-the-art theoretical models built by Zhu and her colleagues allowed them to compare observations with predictions for black hole activity, star formation and shocks. Chandra X-ray observations also independently supported the researchers' interpretation. The results demonstrate that actively growing black holes have a complex cycle of accretion, outflow and interaction with their surrounding galaxies. By separating the effects of black hole radiation, star formation and shocks, the study provides a clearer view of that cycle and its relationship to star formation.

• The study found that star-forming rings or arcs appeared at distances of about 0.8 to 6 kiloparsecs from the galactic center.
• The researchers observed ionized cones of black-hole radiation extending outward from the galaxies' disks.
• The study used a new three-dimensional diagnostic technique to distinguish among three sources: star formation, radiation from the active black hole and excitation by shocks.
• The findings suggest that AGN feedback may contribute to star formation rather than prevent it.
• The study combined high-resolution observations and detailed theoretical models to analyze the data.
• The results demonstrate that actively growing black holes have a complex cycle of accretion, outflow and interaction with their surrounding galaxies.
• The study provides a clearer view of the feedback cycle and its relationship to star formation.

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