ALMA provides detailed look at galaxy formation in the early Universe

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The new observations show the early Universe galaxies in greater detail than ever before(Credit: ESO)

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Astronomers have used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe distant clouds of star-forming gas from just 800 million years after the Big Bang. The findings represent the first time that the objects have been seen as anything more than just faint blotches, and the new data from the observations is set to significantly impact our understanding of the early Universe.

Due to the sheer distance between the telescope and its subject, the galaxies ALMA is watching form were actually born less than a billion years after the Big Bang, during a period known as the epoch of reionisation. During this time, the Universe was flooded with a fog of hydrogen gas, from which the very first galaxies ignited. Until now, not much was known about these earliest of galaxies.

When making the new observations, the astronomers' goal was to study the relationship between the young stars and the huge clumps of gas from which they emerged. To do so, they searched for a faint glow that's a telltale sign of ionized carbon, emitted from star forming clouds.

Focusing in on the galaxy BDF 3299, the team used ALMA to pick up a faint signal from the glowing carbon. Fascinatingly, the glow wasn't emitted from the center of the fledgling galaxy, but was instead focused around one side.

The team believes that the off-center location of the glow can be attributed to a harsh environment created by the newborn stars, with high levels of radiation and supernova explosions disrupting the central clouds.

"This is the most distant detection ever of this kind of emission from a 'normal' galaxy, seen less than one billion years after the Big Bang," said study co-author Andrea Ferrara. "It gives us the opportunity to watch the build-up of the first galaxies. For the first time we are seeing early galaxies not merely as tiny blobs, but as objects with internal structures."

Observations such as this are set to provide an unparalleled insight into the nature of the early Universe, allowing scientists to test predictions and hypotheses about the period using real data, for the very first time.

"This study would have simply been impossible without ALMA, as no other instrument could reach the sensitivity and spatial resolution required." said team member Roberto Maiolino. "Although this is one of the deepest ALMA observations so far it is still far from achieving its ultimate capabilities. In future ALMA will image the fine structure of primodial galaxies and trace in detail the build-up of the very first galaxies."

Source: ESO

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