Missing Oxygen Discovered in 37 Nearby Dwarf Galaxies by Hubble
“Oxygen is produced by stars, which are inside of galaxies. We know that the oxygen had to be inside of the galaxies at some point in the past, so the oxygen must have been ejected,” explained Grace Telford, co-investigator and assistant professor in the Department of Physics and Astronomy at the University of Utah. Researchers analyzing 37 nearby dwarf galaxies using data from the Hubble Space Telescope found that these small systems retain only a small fraction of the oxygen their stars manufactured, according to a paper published in The Astrophysical Journal.
Galactic Winds and Supernova Explosions Drive Out Heavy Elements
Simulations predict that significantly more oxygen should reside within dwarf galaxies, which contain anywhere from a few thousand to hundreds of millions of stars. The findings indicate that supernova-driven galactic winds expel oxygen from low-mass galaxies far more efficiently than existing models currently anticipate. Grace Telford noted that stellar energy is required to eject this material into the space between galaxies.
Why Astronomers Track Oxygen Across the Universe
Oxygen serves as a reliable indicator for how chemical elements distribute across a galaxy because it is the most abundant element after hydrogen and helium, is relatively easy to detect, and has a well-understood production cycle. Kristen Wingfield McQuinn, Galaxies Losing Oxygen via Winds (GLOW) principal investigator and mission head of the Science Operations Center for the Nancy Grace Roman Space Telescope at the Space Telescope Science Institute in Baltimore, Maryland, explained the practical reasons for choosing the element. McQuinn, who also serves as an associate professor at Rutgers University in New Brunswick, New Jersey, stated that tracking oxygen production and distribution helps scientists understand galaxy evolution and the chemical enrichment of the intergalactic medium.
Combining Multiple Space Telescopes to Map Stellar Populations
The research team utilized archival optical imaging data from Hubble to resolve stellar populations and determine star-formation histories and compositions. Researchers also incorporated data from the retired Spitzer Space Telescope, along with ground-based observations from the Very Large Array and the Australian Telescope Compact Array. The 37 dwarf galaxies were specifically chosen because their masses fall within the theoretical threshold where simulations predict supernovae will expel increasing amounts of oxygen, and because they are close enough for Hubble to resolve individual stars.
Frequently Asked Questions About the GLOW Project
Where does the missing oxygen go after leaving dwarf galaxies?
Astronomers know that galaxies expel heavy elements via galactic winds, but it remains unclear whether most of the missing oxygen is in the circumgalactic medium, or if it has been completely ejected from the galaxy’s surroundings.
What makes these 37 dwarf galaxies different from others?
These specific dwarf galaxies are close enough in the nearby universe for the Hubble Space Telescope to resolve their individual stars, whereas the vast majority of known dwarf galaxies are too distant for this level of detailed stellar observation.
Which telescopes will researchers use next to study faint galaxies?
Kristen Wingfield McQuinn plans to use the Nancy Grace Roman Space Telescope to identify faint, tiny systems across a wide swath of the sky, followed by deeper observations using Hubble and the James Webb Space Telescope.
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