Megamaser ‘Nkalakatha’ discovered via MeerKAT

Staff Writer
By Staff Writer, ITWeb
Johannesburg, 07 Apr 2022
Artist’s impression of a hydroxyl maser. (Image source: SARAO)
Artist’s impression of a hydroxyl maser. (Image source: SARAO)

Using the MeerKAT radio telescope, a team of researchers discovered a powerful megamaser – a radio-wavelength laser indicative of colliding galaxies.

The team is from the University of the Western Cape, University of Cape Town, Rhodes University, South African Radio Astronomy Observatory and South African Astronomical Observatory (SARAO), together with colleagues from 12 other countries.

According to SARAO, this is the most distant such megamaser found so far.

It explains that galaxies are vast islands of matter in the universe, and they are made of hundreds of billions of stars, gas and dark matter.

When galaxies merge in collisions of cosmic proportions, the gas they contain becomes extremely dense.

In particular, SARAO says, this can stimulate hydroxyl molecules, made of one atom of oxygen and one atom of hydrogen, to emit a specific radio signal called a maser (a maser is like a laser but emits radio waves instead of visible light).

When that signal is exceedingly bright, it is called a megamaser.

“When two galaxies like the Milky Way and the Andromeda Galaxy collide, beams of light shoot out from the collision and can be seen at cosmological distances,” says Professor Jeremy Darling from the University of Colorado in the US, a megamaser expert and co-author of the study.

“The OH megamasers act like bright lights that say: ‘here is a collision of galaxies that is making new stars and feeding massive black holes’. Hydroxyl megamasers emit light at a wavelength of 18cm. This light belongs to the radio part of the electromagnetic spectrum, and it is the type of light that the MeerKAT radio telescope in the Karoo is designed to capture exceptionally well.”

Probing ‘cosmic vuvuzela’

The Looking at the Distant Universe with the Meerkat Array (LADUMA) team leads one of the big MeerKAT science experiments, which is looking for neutral hydrogen gas in galaxies in one area of the sky, and looking for it very deeply – meaning very far from us, both in space and in time, SARAO says.

It adds that by measuring the neutral hydrogen gas in galaxies from the distant past to now, LADUMA will contribute to our understanding of the evolution of the universe.

The research team comprises scientists from South Africa, Australia, Chile, France, Germany, India, Italy, Japan, the Netherlands, South Korea, Spain, the UK and the US.

“LADUMA is probing hydrogen within a single ‘cosmic vuvuzela’ that extends to when the universe was only a third of its present age,” says associate professor Sarah Blyth from the University of Cape Town.

To look for hydrogen, the team looks for light with a wavelength of 21cm that has been stretched to longer wavelengths by the expansion of the universe.

However, light from other atoms and molecules is also present, and in their very first observation with MeerKAT, the team detected bright emission from hydroxyl molecules that had been even more stretched from its original wavelength of 18cm.

Dr Marcin Glowacki, previously a researcher at the Inter-University Institute for Data-Intensive Astronomy and University of the Western Cape, and now based at the Curtin University node of the International Centre for Radio Astronomy Research, led the investigation.

He explains: “It’s impressive that in a single night of observations with MeerKAT, we already found a redshift record-breaking megamaser. The full 3 000+ hour LADUMA survey will be the most sensitive of its kind.”

According to SARAO, when they saw this signal in the data coming from the telescope, and confirmed it was coming from hydroxyl, the team realised they had a megamaser on their hands.

To make this discovery, the team had to run complex scientific algorithms on large amounts of data. This was made possible by the Inter-University Institute for Data-Intensive Astronomy research cloud computing facility.

This facility exists to help the South African research community do as much science as possible with the MeerKAT, and with the upcoming Square Kilometre Array in the future.

Follow-up observations

The host galaxy of “Nkalakatha” is known to have a long tail on one side, visible in radio waves, says SARAO, adding it is about 58 thousand billion billion (58 followed by 21 zeros) kilometres away, and the megamaser light was emitted about five billion years ago when the universe was only about two-thirds of its current age.

“We have already planned follow-up observations of the megamaser, and as LADUMA progresses, we will make many more discoveries,” notes Dr Glowacki.

This is the first time a megamaser has been detected at that distance from its emission at 18cm wavelength.

The authors of the study point out it is not surprising they found such a bright megamaser, given how powerful the MeerKAT is, but the telescope is very new, so this find is hopefully one of many more to come.

“MeerKAT will probably double the known number of these rare phenomena. Galaxies were thought to merge more often in the past, and the newly discovered OH megamasers will allow us to test this hypothesis,” comments Darling.