Q&A: Astronomers study the early gas to study how galaxies are born

Studying the environment is not easy, also because of the long distances involved. If you want to learn about the galaxies where stars and galaxies form, you often have to look at the regions of the universe that do not have any light, due to the absence of the aforementioned stars.

Astronomers compensate for this by using spectroscopy, which allows them to “see” not only wavelengths of light that are invisible to the naked eye, but also detect energy from radio waves to gamma waves. In this way, they can analyze the most distant objects in the sky.

Recently Nature research, NC State astronomer Rongmon Bordoloi was part of a team that identified “primordial gas” far from any galaxies. By identifying and studying how these gases are formed, the team hopes to unravel the mystery of how galaxies are born, and what they are made of on a fundamental scale.

Bordoloi sat down with The Abstract to answer questions about the latest research.

Comment: In your paper, you saw ‘primordial gases’ emerging from new galaxies. What were these early spirits? How many were there and how did you identify them?

Bordoloi: We found two clusters of primordial gas far away from the nearest galaxies. These “clouds” are clouds of atomic gas that are relatively small in size compared to the galaxy; they are a factor of 10 or less than the standard galaxy.

We detected them using the ALMA Radio Telescope array (Atacama Large Millimeter Array), a large radio telescope array located in the Atacama Desert in Chile. We detected the forbidden transition of the ionized carbon atom, which produces a unique signature. That signature means the signal is coming from a high gas cloud.

That visible signature combined with the lack of “visible” stars when we observed the same area with the Hubble Space Telescope, means that an ancient gas cloud/galaxy existed in the area.

TA: How do these gases form?

Bordoloi: That’s a good question. How these clouds are formed is still unknown. These clouds are detected—as I explained above—by finding gas that is restricted in infrared light. But they don’t emit any light or UV light (that we can detect), indicating that these clouds are starless.

One theory is that these dense clouds form when gas cools from the core of galaxies (the vast cosmic web, where most of the bars in the early universe reside). Or, they may have formed from dense clouds of gas excited by intense light from galaxies.

TA: Do these primordial gas clouds help form new galaxies? If so, why?

Bordoloi: Yes they will play a role in the formation of galaxies. Gravity means that these clouds will eventually collapse into galaxies and form stars, thereby increasing the mass of the galaxies. Indeed, this is one of the primary processes (gas falling onto galaxies), through which galaxies grow from small galaxies in the early universe to become giant galaxies like the Milky Way today.

TA: What do these findings tell us about the early universe?

Bordoloi: These large gas clouds are located near several other galaxies, and the space between these galaxies contains hot plasma (100,000 degrees Kelvin) that we have also detected. This discovery shows that in the early universe there are many compounds that do not mix with air. For example, supernovae exploding in early galaxies can release a large amount of ionized plasma from the galaxy, which eventually flows back into star clusters and forms the next generation of stars. So the early universe was a very dynamic environment—a kind of carbon recycling machine, and this “machine” eventually created the complex atoms and molecules that are abundant today in our solar system.

TA: What do you think was the most exciting part of this discovery?

Bordoloi: The discovery of these dense gas clouds was completely unexpected, and made us think deeply about how such large gas clouds could exist in the first place. Note that this project is possible because we can combine observations from space (Hubble Space Telescope imaging), ground observations and millimeter depth observations (with ALMA).

The ability to conduct multi-wavelength research is one of the unique features of this project that provided unexpected and exciting science. To me the collaboration of combining all the elements and wavelengths together to make a coherent scientific experiment is an amazing part of this work.