JWST Reveals Hidden History of Galaxy Merger in Centaurus A

• Centaurus A (NGC 5128), a prominent starburst galaxy located 11 million light-years away, shows clear evidence of a past galaxy merger through new JWST observations.
• Galaxy mergers occur over hundreds of millions of years, involving gravitational interactions, the formation of tidal tails, and eventual "violent relaxation" that triggers rapid star formation.
• While visible light observations are often obscured by thick dust, JWST infrared capabilities allow astronomers to peer through that dust to uncover structural signatures of past mergers.

The Merger Process

• Gravitational interaction: Galaxies on a collision course create tidal tails or bridges of gas and stars during their first pass.
• Orbital decay: Friction between stars and dark matter reduces energy, causing galaxies to loop back and collide repeatedly.
• Violent relaxation: The gravitational potential shifts, forcing stars into random orbits and increasing the density of star-forming gas, leading to starburst activity.

Insights from JWST

• Infrared imaging: The Mid-Infrared Instrument (MIRI) revealed previously unseen structures in Centaurus A, including wispy filaments, a central parallelogram feature, and a mysterious S-shaped loop.
• Spectroscopy: JWST’s spectrograph measured the movement of ionized gas and molecular hydrogen near the center, helping scientists understand the complex relationship between the galaxy's active supermassive black hole and star formation.
• Chemical history: Centaurus A contains a bimodal distribution of globular clusters, with one metal-poor population (ancient) and one metal-rich population (billions of years younger), providing further confirmation of a past merger event.