Hubble finds 37 nearby dwarf galaxies retain little of their oxygen in the GLOW project
Astronomers using Hubble measured oxygen in 37 nearby dwarf galaxies and found far less than simulations predict, pointing to stronger supernova-driven winds.
Researchers using NASA's Hubble Space Telescope studied 37 nearby dwarf galaxies, which contain from a few thousand to hundreds of millions of stars, and found that much of the oxygen they expected is missing, according to science.nasa.gov. The paper was published in The Astrophysical Journal. science.nasa.gov
science.nasa.govscience.nasa.govOpen source ↗ Simulations predict that significantly more oxygen, a tracer of a wider set of heavy elements, should reside in these galaxies.
How the GLOW project traced oxygen
The work is part of the Galaxies Losing Oxygen via Winds (GLOW) project, funded by NASA and the National Science Foundation. The team traced oxygen in stars, in the gas between stars, and in the space between galaxies. Oxygen is the most abundant element after hydrogen and helium, is relatively easy to detect and measure, and its production is well understood, which makes it a reliable indicator of how chemical elements are distributed in a galaxy.
The researchers used archival optical imaging from Hubble to resolve stellar populations and determine star-formation histories and compositions. They added data from the retired Spitzer Space Telescope and from the ground-based Very Large Array and Australian Telescope Compact Array. The galaxies were selected because their masses fall in the range where theory predicts that a growing share of oxygen is expelled by supernova explosions. All 37 are close enough for Hubble to resolve individual stars, which is not true for most known dwarf galaxies.
Where the missing oxygen may have gone
According to the study, galactic winds driven by supernovae remove oxygen from low-mass galaxies more effectively than current models predict. Dwarf galaxies hold onto only a small fraction of the oxygen made by their stars. science.nasa.gov
science.nasa.govscience.nasa.govOpen source ↗ Grace Telford of the University of Utah, a co-investigator, said that typically about 15 percent of the oxygen produced by stars in these galaxies is still found inside them today, mostly in the gas, with smaller amounts in stars and dust.
A 2014 study of Milky Way-like star-forming galaxies found that they lost a large fraction of their oxygen, some of it located in the diffuse gas halo outside the disk, called the circumgalactic medium. GLOW extends this work to low-mass galaxies across a wide range of masses and environments. Oxygen has been measured in the circumgalactic medium of dwarf galaxies before, but it remains unclear whether most of the missing oxygen is there or has left the galaxy's surroundings entirely.
GLOW principal investigator Kristen Wingfield McQuinn has an approved program to use the Roman Space Telescope to find even fainter, lower-mass galaxies nearby, and plans to follow them up with Hubble and the James Webb Space Telescope. Telford is using Hubble to observe individual massive stars in some of the GLOW targets.
