ALMA Telescope ‘Sees’ Galaxies Collide in Early Universe

It is the earliest example of merging galaxies yet discovered.

A team of researchers observed, thanks to the Atacama Large Millimeter / submillimeter Array (ALMA), signals of oxygen, carbon, and dust in a galaxy of the primitive Universe, 13,000 million years ago.

ALMA -the largest astronomical project in existence- is a single telescope of revolutionary design, composed of 66 high precision antennas located on the Chajnantor plateau, 5000 meters altitude in northern Chile.

This is the oldest galaxy where this combination of signals has been detected.

By comparing the different signals, the researchers came to the conclusion that they are actually two colliding galaxies, the oldest discovered to date.

Galactic Collision

Researcher Takuya Hashimoto, from Waseda University, Japan, and his team used ALMA to observe B14-65666, an object located 13 billion light years from Earth, in the constellation Sextans, the Sextant.

Since the speed of light is finite, the signals of B14-65666 captured today had to travel for 13 billion years to reach us.

In other words, these waves provide us with an image of the galaxy as it was 13 billion years ago, that is, only 1 billion years after the Big Bang.

This is a composite image of B14-65666 showing the distributions of dust (red), oxygen (green), and carbon (blue), observed by ALMA and stars (white) observed by the Hubble Space Telescope. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Hashimoto et al.
This is a composite image of B14-65666 showing the distributions of dust (red), oxygen (green), and carbon (blue), observed by ALMA and stars (white) observed by the Hubble Space Telescope. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Hashimoto, et al.

‘Sniffing out’ the cosmic environment

ALMA detected radio emissions of oxygen, carbon, and dust in B14-65666. This is the oldest galaxy where this combination of signals has been detected. Multiple signals are important for astronomers because they provide complementary information.

Further analysis of the data revealed that the emissions are divided into two groups.

In observations made previously with the Hubble Space Telescope (HST), two stellar clusters had been detected in B14-65666.

Now, with the three signals detected by ALMA, the researchers were able to demonstrate that the two groups of signals are part of the same system, although they have different speeds of displacement.

This indicates that the two groups correspond to two galaxies in the process of fusion which points to the oldest collision galaxies that have been detected so far.

The research team calculates that the total star mass of B14-65666 is equivalent to less than 10% of the star mass of the Milky Way, which shows that B14-65666 is in the early stages of its evolution.

Now, despite being in its infancy, B14-65666 produces stars 100 times faster than the Milky Way.

This star formation activity is another important indication of galactic fusion since compression of the gas in colliding galaxies naturally produces star formation bursts.

Via
ALMA
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