Hubble finds oxygen missing from 37 nearby dwarf galaxies
A Hubble study of 37 dwarf galaxies finds far less oxygen than models predict, suggesting supernova-driven winds expel the element more efficiently than expected.
The story in focus
NASA reports that Hubble studied 37 nearby dwarf galaxies and found much of their expected oxygen is missing. Researchers attribute the loss to supernova-driven galactic winds that remove oxygen from low-mass galaxies more effectively than current models predict, according to a paper in The Astrophysical Journal.
- Hubble observations of 37 nearby dwarf galaxies show far less oxygen than simulations predict.
- Supernova-driven galactic winds appear more effective at expelling oxygen from low-mass galaxies than models forecast.
- Oxygen serves as a tracer for a broader set of heavy elements produced by stars.
- The study used Hubble archival optical imaging plus data from Spitzer, the Very Large Array and the Australian Telescope Compact Array.
- It remains unclear whether most missing oxygen sits in the circumgalactic medium or was ejected beyond it.
What Hubble observed
NASA reports that researchers using the Hubble Space Telescope studied 37 nearby dwarf galaxies, small systems containing a few thousand to hundreds of millions of stars, and found much of the oxygen they expected is absent. The paper was published in The Astrophysical Journal.
Simulations predict significantly more oxygen should reside in these galaxies. Oxygen is the most abundant element after hydrogen and helium and is relatively easy to detect, making it a reliable tracer of how heavy elements are distributed.
How the oxygen escaped
The Galaxies Losing Oxygen via Winds (GLOW) project, funded by NASA and the National Science Foundation, traced oxygen across stars, gas between stars, and space between galaxies. Co-investigator Grace Telford of the University of Utah said the oxygen must have been ejected, requiring energy from massive stars and supernova explosions.
According to the study, galactic winds unleashed by supernovae are apparently more effective at removing oxygen from low-mass galaxies than current models predict. Principal investigator Kristen Wingfield McQuinn said tracing oxygen helps reveal how galaxies enrich the intergalactic medium.
Next steps
The team combined Hubble archival optical imaging with data from the retired Spitzer Space Telescope, the Very Large Array and the Australian Telescope Compact Array. The 37 galaxies were selected because their masses fall where theory predicts increasing oxygen loss, and because Hubble can resolve their individual stars.
McQuinn has an approved program to use the Roman Space Telescope to find fainter, lower-mass galaxies, with follow-up observations planned using Hubble and the James Webb Space Telescope. Telford plans Hubble observations of the massive stars that produce and eject oxygen.
Did the study determine where the missing oxygen ended up?
No. Researchers say it remains unclear whether most of the missing oxygen sits in the circumgalactic medium around dwarf galaxies or has been completely ejected beyond their surroundings.
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