For the first time we can observe and disentangle the different components contributing to the earliest phases of galaxy formation
- Roberto Maiolino
The new observations will allow astronomers to start to see how the first galaxies were built up and how they cleared the cosmic fog during the era of reionisation. This is the first time that such galaxies have been seen as more than just faint blobs.
When the first galaxies started to form a few hundred million years after the Big Bang, the Universe was full of a fog of hydrogen gas. But as more and more brilliant sources — both stars and quasars powered by huge black holes — started to shine they cleared away the mist and made the Universe transparent to ultraviolet light. Astronomers call this the epoch of reionisation, but little is known about these first galaxies, and up to now they have just been seen as very faint blobs. But now new observations using the Atacama Large Millimetre/submillimetre Array (ALMA) are starting to change this.
A team of astronomers led by Roberto Maiolino from the University’s Cavendish Laboratory and Kavli Institute for Cosmology trained ALMA on galaxies that were known to be seen only about 800 million years after the Big Bang. The astronomers were not looking for the light from stars, but instead for the faint glow of ionised carbon coming from the clouds of gas from which the stars were forming. They wanted to study the interaction between a young generation of stars and the cold clumps that were assembling into these first galaxies.
They were also not looking for the extremely brilliant rare objects — such as quasars and galaxies with very high rates of star formation — that had been seen up to now. Instead they concentrated on rather less dramatic, but much more common, galaxies that reionised the Universe and went on to turn into the bulk of the galaxies that we see around us now.
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Image:The central object is a very distant galaxy, labelled BDF 3299. The bright red cloud just to the lower left is the ALMA detection of a vast cloud of material that is in the process of assembling the very young galaxy
Credit: ESO/R. Maiolino
Reproduced courtesy of the University of Cambridge
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