Researchers using NASA’s Hubble Space Telescope published a study on Monday revealing that much of the expected oxygen in 37 nearby dwarf galaxies is missing. The study analyzed archival optical imaging data from Hubble, data from the retired Spitzer Space Telescope, and information from ground-based arrays.
The findings show that dwarf galaxies retain only a small fraction of the oxygen produced by their stars. The discovery helps astronomers understand galaxy evolution and how galaxies enrich the intergalactic medium, according to Kristen Wingfield McQuinn, principal investigator of the Galaxies Losing Oxygen via Winds project. McQuinn is the mission head of the Science Operations Center for the Nancy Grace Roman Space Telescope at the Space Telescope Science Institute and an associate professor at Rutgers University.
Current simulations predict that significantly more oxygen should reside in these low-mass galaxies. Researchers concluded that galactic winds unleashed by supernovae are more effective at removing oxygen from low-mass galaxies than current models predict.
Oxygen must have been ejected by energy from massive stars and supernova explosions, said Grace Telford, a co-investigator and assistant professor at the University of Utah. The research team selected the 37 dwarf galaxies because they are close enough for Hubble to resolve their individual stars and their masses fall in a range where simulations predict oxygen expulsion.
Oxygen was chosen for the study because its production is well understood and it is relatively easy to detect, making it a reliable indicator of chemical distribution. The study was published in The Astrophysical Journal and funded by NASA and the National Science Foundation.
While a previous study found that Milky Way-like galaxies lost a large fraction of their oxygen to diffuse haloes of gas called the circumgalactic medium, it remains unclear if the missing oxygen from dwarf galaxies is in this region or completely ejected. In the future, McQuinn hopes to use the Roman Space Telescope to find fainter systems and observe their stars with the James Webb Space Telescope. Telford plans to use Hubble to observe individual massive stars that produce and eject oxygen from host galaxies.