Astronomers have employed the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) to perform deep spectroscopic observations of a peculiar spiral galaxy known as W2246f. Results of the observational campaign, published May 27 on the pre-print server arXiv, offer new insights into how this galaxy evolved and shed more light on its nature.
A mystery in the foreground
W2246f, also known as Leda 1044720, is a spiral galaxy located some 1.2 billion light years away. The galaxy is about 50,000–70,000 light years in diameter and lies in the foreground of WISE J224607.57−052635.0—a hot, dust-obscured galaxy at a redshift of 4.6.
Given that very little is known about W2246f, an international group of astronomers led by Evelyn J. Johnston of the Diego Portales University in Chile decided to employ MUSE to investigate this galaxy in detail.
“The datacube used in this study covers the entire galaxy with high spatial resolution (∼ 0.2 arcsec/pixel), with the deep exposure time ensuring good signal even in the outermost regions,” the researchers explain.
What did MUSE reveal?
Johnston’s team used the collected MUSE data to carry out analysis of the stellar and gas kinematics, the stellar populations and the gas properties to better understand the nature of W2246f in the first place. The observations with MUSE were carried out between July and September 2022.
Studying the visual morphology and the stellar and gas kinematics, the astronomers found no obvious signs of distortion. This suggests that it is unlikely that W2246f has undergone a recent interaction within the last 1 billion years.
Next, the team analyzed the stellar population of W2246f. They found that the galaxy shows relatively old mass-weighted ages across the whole system, with older ages in the bulge-dominated region at the center and no strong gradient across the disk. This finding indicates that W2246f formed the majority of its mass about 6–7 billion years ago.
According to the paper, the mass-weighted metallicities in the inner part of W2246f show a slight positive gradient before decreasing again throughout the rest of the disk. This suggests that in that region the star formation has been truncated, reducing the chemical enrichment there relative to other parts of the disk that have ongoing star formation.
The astronomers note that the gas metallicity and star formation rate density also drop in the central region of W2246f where the older luminosity-weighted stellar populations are found.
Classifying W2246f
All in all, the authors of the paper conclude that their findings point to a central low-ionization emission-line region (cLIER) galaxy classification for W2246f.
“In summary, these results indicate that W2246f is a nice example of a cLIER galaxy, where the central kpc or so is dominated by old, metal-poor stars with little star formation and where the central LIER emission is primarily powered by hot evolved (pAGB) stars, while the rest of the disk is displaying ongoing star formation,” the scientists write.
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Publication details
Evelyn J. Johnston et al, A Deep Study of the Spiral Galaxy W2246f, arXiv (2026). DOI: 10.48550/arxiv.2605.29014
Journal information:
arXiv
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MUSE maps spiral galaxy W2246f, uncovering old core and ongoing star formation across disk (2026, June 6)
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