"Dwarf galaxy I Zw 18 is the least abundant in metals (in astrophysics, elements heavier than hydrogen and helium) in the nearby universe, and one of the most akin to the primeval galaxies," said Carolina Kehrig, researcher at the Institute of Astrophysics of Andalusia, according to a press release. Kehrig is the leader of the new study "The Extended HeII 4686Å-Emitting Region in I Zw 18: Clues for Peculiar Ionizing Sources," published in the Astrophysical Journal Letters.
The presence of ionized helium in the small galaxy suggests that enough radiation is being emitted by objects in the galaxy - radiation intense enough to knock off electrons from the helium atoms. "In this study we propose a new interpretation of the origin of this radiation in galaxy I Zw 18, a subject which is still enigmatic," Kehrig said, according to the press release.
The PMAS integral field spectrograph of the 3.5-meter telescope at the Calar Alto Observatory (CAHA), was used to create the first detailed map of the large area inside I Zwicky 18. "Our data points to the fact that extremely hot stars, such as supermassive stars with low metal content or massive stars practically devoid of metals may hold the key to the enigma of the excitement of helium on I Zw 18, even though the existence of these stars has not yet been confirmed by observations on any galaxy," Kehrig said, according to the press release.
First generation stars (Population III stars) composed of hydrogen and helium with masses hundreds of times greater than the sun are thought to have played a key role in the "reionization" of the universe, of which little is known.
Observations of the dwarf galaxy could clue scientists in to the origins of our universe.
