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#Science

ALMA peeks inside universe’s oldest galaxies

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Astronomers have detected the earliest known galaxies in the universe – formed just 800 million years after the Big Bang – using European Southern Observatory’s Atacama Large Millimeter/submillimeter Array (ALMA) in a bid to understand how the first galaxies were built up and how they cleared the cosmic fog during the era of reionization.

Researchers believe that after Big Bang and before star and galaxy formation was at its peak, the universe was full of hydrogen gas. As more and more stars begin the form followed by increased radiation from quasars powered by huge black holes, the hydrogen gas started to clear away making the universe transparent to ultraviolet light from the stars.

This view is a combination of images from ALMA and the Very Large Telescope. The central object is a very distant galaxy, labelled BDF 3299, which is seen when the Universe was less than 800 million years old. 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

This view is a combination of images from ALMA and the Very Large Telescope. The central object is a very distant galaxy, labelled BDF 3299, which is seen when the Universe was less than 800 million years old. 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

Astronomers call this timeline as the epoch of reionization, 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 power of ALMA are starting to change this.

Roberto Maiolino from Cavendish Laboratory and Kavli Institute for Cosmology, University of Cambridge along with their team trained ALMA on galaxies that were known to be seen only about 800 million years after the Big Bang. One such galaxy they spotted was BDF 3299, which was picked up by ALMA as a faint but clear signal from the glowing carbon.

Researchers observed that the glow wasn’t coming from the center of the galaxy, but rather from one side and the reason of the loft-sided nature – researchers believe – is because the central clouds are being disrupted by harsh environment created by the newly formed stars.

Researchers combined their observations from ALMA with computer simulations and have been able to understand in detail key processes occurring within the first galaxies. Dubbed as a typical example of early galaxy, the BDF 3299 provided astronomers the means to understand the effects of radiation from stars, the survival of molecular clouds, the escape of ionizing radiation and the complex structure of the interstellar medium.