MUSE Maps Spiral Galaxy W2246f, Uncovering Old Core and Ongoing Star Formation Across Disk

Why It Matters

The discovery clarifies how some spirals sustain star formation in their disks while their cores age, refining models of secular galaxy evolution and informing the classification of cLIER systems.

Key Takeaways

• W2246f shows no recent interaction within 1 billion years.
• Central bulge hosts 6–7 billion‑year‑old, metal‑poor stars.
• Disk maintains ongoing star formation and higher gas metallicity.
• Galaxy classified as cLIER, powered by evolved pAGB stars.
• MUSE achieved 0.2″ spatial resolution across entire galaxy.

Pulse Analysis

MUSE’s integral‑field spectroscopy on the VLT provides a three‑dimensional view of galaxies, capturing both spatial and spectral information in a single exposure. By covering the full extent of W2246f at 0.2‑arcsecond resolution, researchers obtained unprecedented detail on stellar motions, gas dynamics, and chemical composition. This level of granularity is rare for a galaxy at a distance of over a billion light‑years, allowing astronomers to dissect the interplay between old stellar populations and fresh star‑forming regions without the confusion of overlapping structures.

The analysis uncovered a striking dichotomy: the central kiloparsec is dominated by ancient, metal‑poor stars with suppressed star formation, while the surrounding disk exhibits active star‑forming clumps and a modest rise in gas metallicity. Such a pattern aligns with the cLIER classification, where low‑ionization emission originates from hot post‑AGB stars rather than active galactic nuclei. The positive metallicity gradient in the inner region, followed by a decline outward, suggests that the galaxy’s core experienced an early burst of star formation that later quenched, leaving the outer disk to continue building mass over billions of years.

These findings have broader implications for galaxy evolution theory. They demonstrate that secular processes, not just major mergers, can produce the mixed-age, mixed‑metallicity profiles observed in many nearby spirals. By establishing a nearby benchmark, W2246f offers a reference point for interpreting high‑redshift galaxies that appear similarly compact yet star‑forming. Future MUSE campaigns and complementary observations with JWST and ALMA will likely expand the sample of cLIER galaxies, sharpening our understanding of how stellar feedback and internal dynamics shape the life cycles of disk galaxies.