- 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.
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