Molecules show the way to star factories in distant galaxies –

When the universe was young, galaxies were different from the stately spiral galaxies of today, which are filled with softly glowing suns and colorful gas clouds.

Initially, new stars formed at a rate hundreds of times faster than the current universe. Most of this happened behind thick layers of dust, which presents a real challenge for scientists who want to investigate the secrets of these stellar factories.

But with the help of powerful telescopes, astronomers can now better understand how so many stars could be created in distant galaxies.

New measurements of distant galaxies

In one study, an international research team, led by Chalmers University of Technology, describes new measurements at the Noema Observatory in France.

Researchers measured light from two bright galaxies in the early universe. Both had a very high rate of star formation.

– We knew that these galaxies were highly efficient star factories, perhaps among the most extreme in the universe. In order to find out how they work, we measured their light at wavelengths of about one millimeter, in the hope of gathering new evidence, says astronomer Qintao Yang of Chalmers.

Dramatic chemistry in galaxies

The measurements exceeded the researchers’ expectations. In the light recorded from the two galaxies, they were able to see traces of different types of molecules.

When stars formed, light at different wavelengths was sent from clouds of gas and dust where stars were born, deep into galaxies.

– It is a magnificent explosion of colours, with shades that the human eye cannot see. By combining our observations with our knowledge of physics and chemistry, we can understand what the colors mean, and see the differences that exist between different galaxies, explains Sergio Martin from the research team.

A record number of molecules were found

By analyzing the spectrum of both galaxies – the individual colors that together make up their light – the researchers were able to identify 13 different molecules. Many of them have never been discovered before in such distant galaxies.

The molecules can provide new information about the physical and chemical conditions in these galaxies. Each molecule provides different clues about the temperature, pressure and density of interstellar space. They can also show how starlight, radiation, and matter interact.

Interpreting signals is a challenge. Here we see a part of the electromagnetic spectrum that is difficult to observe in nearby galaxies. But thanks to the expansion of the universe, light from distant galaxies like these is shifting to longer wavelengths, which we can see with radio telescopes that observe in submillimeter light, says Chentao Yang.

Illustration shows particles in distant galaxy NCv1.143, over an image of a similar nearby galaxy, NGC 572. Images: ESA/Hubble, NASA, L. Ho. Editing: R. Cumming

More about molecules

More than a hundred different molecules have been discovered in space, in interstellar gas clouds. In the current study, astronomers identified 13 molecules: carbon monoxide (CO), cyano radical (CN), ethylene radical (CCH), hydrogen cyanide (HCN), formyl cation (HCO+), hydrogen isocyanide (HNC), carbon monosulfide (CS), water (H2O), hydronium ion (H3O+), nitric oxide (NO), diazenylium (N2H+), methylidene radical (CH) and cyclopropylenediline (c-C3H2).

The two galaxies are so far away that it took nearly 13 billion years for their light to reach us.

Looking at these galaxies is less like a night under the stars and more like seeing a city lit up with neon lights, says astronomer Susan Aalto of Chalmers.

Star factories are full of dust

Astronomers are used to taking pictures of star factories in our galaxy, such as the Orion Nebula and the Carina Nebula. But the star factories of the two distant galaxies now examined differ in many ways. They are larger, brighter and full of dust.

Nebulae such as Orion and Carina glow thanks to ultraviolet light emanating from hot, newborn stars. But in the two distant galaxies, ultraviolet rays cannot pass through layers of dust. Much of the illumination is due to cosmic rays, high-energy particles that can be created by exploding stars, or near supermassive black holes, says Suzanne Aalto.

Although these galaxies are rare, researchers plan to study more in the future. This will be done with the help of the highly sensitive telescopes NOEMA in France and ALMA in Chile.

Scientific study:

Sunrise: The rich molecular inventory of dusty, high-redshift galaxies revealed by broadband spectral line surveys, Astronomy and astrophysics.

communication:

Chentao Yang, astronomer at Chalmers University of Technology, [email protected]

Robert Cumming, astronomer and correspondent at Onsala Space Observatory, Chalmers University of Technology, [email protected]