Distant galaxies shed light on cosmic dark ages

Distant galaxies shed light on cosmic dark ages

Image of the plot in a false color, covering 2 square degrees. The small white marks indicate the positions of 23 Lyman alpha emitters (AIL). The inset shows the two largest AILs, reaching 0.5 arc-minutes, and white circles — 5 arc-seconds in diameter.

In the study of a distant universe, scientists found that small star-forming galaxies were present in huge numbers when the age of space was only 800 million years.

300,000 years after the Big Bang, space still remained dark. Until that time, there were no stars and galaxies, and the universe was inhabited by neutral gaseous hydrogen. But at a certain point, the first galaxies were born, whose energy rays ionized the environment and lit up space.

This event happened between about 300 million and 1 billion years after the beginning of everything. Such a big gap complicates their search. Moreover, the problem also creates intergalactic gas, which was originally neutral.

To get closer to distant events, scientists take an indirect approach. They study the demographics of small galaxies with star formation to understand when the intergalactic gas launched the ionization process. If such galaxies, glowing from the hydrogen line of Lyman's alpha-radiation, are surrounded by neutral gaseous hydrogen, then Lyman photons quickly scatter, closing the object. When the gas is ionized, the fog disappears and the search is much easier to perform. A new study made it possible to find 23 candidates in the Lyman gamma and alpha radiation, created 800 million years after the beginning of everything.

Distant galaxies shed light on cosmic dark ages

Historical milestones of the Universe (scale not met). The intergalactic gas was in a neutral state 300,000 years after the Big Bang and before the first stellar generation. After a billion years, it is completely ionized.

Researchers also found that Lyman's alpha-radiation was 4 times less common at around 800 million years than a billion years (in redshift).

The data show that the “fog” was already rising when the age of space reached 5% of today's. Gas was ionized by 50% with a red shift at z ~ 7, that is, most of the first galaxies formed early (800 million years after the Big Bang).

Scientists continue to explore distant galaxies, trying to look as far as possible into the past. The current feature of ionization is 800 million years. Further studies may help move this mark.

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