The life cycle of molecular gas in the barred spiral galaxy Messier 83 appears to be driven mainly by the galaxy’s large-scale structure and rotation, rather than by feedback from newborn stars, according to a new study.
This ALMA image shows the barred spiral galaxy Messier 83. Image credit: ALMA / ESO / NAOJ / NRAO / Koda et al.
Messier 83 is located approximately 15 million light-years away in the southern constellation of Hydra.
Also known as the Southern Pinwheel Galaxy, M83, NGC 5236, LEDA 48082 or UGCA 366, the galaxy is about twice as small as the Milky Way.
Messier 83 was discovered by the French astronomer Nicolas Louis de Lacaille on February 17, 1752.
It has an apparent magnitude of 7.5 and is one of the brightest spiral galaxies in the night sky. It can be observed using a pair of binoculars most easily in May.
“Messier 83 is one of the brightest galaxies in the night sky, but this image — taken with the Atacama Large Millimeter/submillimeter Array (ALMA) — doesn’t show how the galaxy looks in the light our eyes can see,” Dr. Jin Koda of Stony Brook University and colleagues said in a statement.
“Instead, it depicts the light emitted by cold gas molecules, the ingredients of star formation.”
The astronomers used ALMA to map Messier 83’s molecular gas at a resolution of about 150 light-years.
They compared two carbon monoxide emission lines, whose ratio traces the gas’s density and temperature.
The ratio is very high at the galaxy’s center, drops in the bar, rises again near the bar’s end, and falls in the outer disk where spiral arms dominate.
Because this pattern is synchronized with galactic rotation, the researchers conclude it is set largely by galactic structure and dynamics.
Messier 83 closely resembles the Milky Way, and the results agree with earlier studies of our own Galaxy and other barred spirals.
“We are interested in molecular gas clouds as virtually all stars are born from their collapse,” the scientists said.
“Once stars form, they heat up their surroundings, making it harder for gas to condense and form further stars.
“This, combined with galactic dynamics that continually stirs gas, controls the growth of galaxies.”
“ALMA allows us to map how the density and temperature of these gas clouds change in different locations within a galaxy, such as the central regions, the spiral arms, or the space between them.”
“This in turn helps us understand whether stars form differently in different galactic environments.”
The team’s results were published June 10, 2025 in the Astrophysical Journal.
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Jin Koda et al. 2026. Dynamically Driven Evolution of Molecular Gas in the Barred Spiral Galaxy M83 Traced by CO J = 2-1/1-0 Line Ratio Variations. ApJ 986, 29; doi: 10.3847/1538-4357/add1dc
