1805.05966
The onset of star formation 250 million years after the Big Bang
Hashimoto, et al
A fundamental quest of modern astronomy is to locate the earliest galaxies and study how they influenced the intergalactic medium a few hundred million years after the Big Bang. The abundance of star-forming galaxies is known to decline from redshifts of about 6 to 10, but a key question is the extent of SF at even earlier times, corresponding to the period when the first galaxies might have emerged. Present spectroscopic observations of MACS1149-JD1, a gravitationally lensed galaxy observed when the Universe was less than 4% of its present age. Detect an emission line of doubly ionized oxygen at a z of 9.1096±0.0006, with an uncertainty of one standard deviation. This precisely determined redshift indicates that the red rest-frame optical color arises from a dominant stellar component that formed about 250 million years after the Big Bang, corresponding to a redshift of about 15. The results indicate that it may be possible to detect such early episodes of SF in similar galaxies with future telescopes.
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