Some 13,300 million years ago the first galaxies formed, composed almost entirely of hydrogen and helium, the primary elements that emerged after the Big Bang. Their study, today, it is technically very complex because of its great distance, but the observation of similar galaxies in the local universe is unfolding as an excellent shortcut to know them.
“The dwarf galaxy is the poorest IZw18 galaxy metals (in astrophysics, heavier than hydrogen and helium) in the nearby universe, and one that most resembles the first galaxies. So their study allows us to glimpse the conditions that existed in the early universe, “notes Carolina Kehrig, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who heads a research analyzing the properties of IZw18.
It has been discovered in this small nearby galaxy a large region of ionized helium, a common but distant
This study found in this small nearby galaxy a very large region of ionized helium, something more common in very distant galaxies and low metal abundance. The ionization of helium requires the presence of objects that emit a sufficiently intense radiation to boot electrons from helium atoms. “In this paper we give a new interpretation for the origin of this radiation in the galaxy IZw18, an issue that remains unknown”.
Using the PMAS integral field spectrograph of the 3.5 m telescope of Calar Alto Observatory (CAHA), researchers have obtained the first detailed map of this region IZw18 and reviewed the possible sources ionizing.
The conventional sources of ionization, as Wolf-Rayet stars are -stars very intensos- very massive stellar winds and shocks generated by supernova remnants, can not provide all the energy needed to generate the halo IZw18 ionized helium, so that researchers shuffled other options.
The problem of excitation of helium
“Our data suggest that extremely hot stars like supermassive stars While low metallicity massive stars or virtually no metals, can hide the key to solving the problem of excitation of helium in IZw18, although the existence of these stars has not yet been confirmed observationally in any galaxy. “
You try to very hot stars similar to the first generation stars (called Population III stars) and, according to theoretical models, would consist only of hydrogen and helium and could be hundreds of times the sun’s mass. It is believed that these stars were instrumental in the “reionization” of the universe, a time during which the first stars and galaxies were visible, and still remains poorly understood.
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