Just as it was “only” two billion years after the Big Bang, a mysterious and very distant object in the universe is hidden from even the most advanced instruments. Its properties were finally disclosed in a published SISSA study. Astrophysical Journal.

An extremely distant celestial body, still in the young universe, one-sixth the size of the present universe. The object is so dark that it is almost invisible even for very advanced devices. Its nature has long been the subject of debate, but the SISSA research team, led by Professor Andrea Lapi, who studies the formation and evolution of galaxies, was finally able to determine its basis with the help of surveys with the ALMA interferometer. features. It is a young star-forming galaxy, compact and rich in interstellar dust, about 1,000 times faster than the Milky Way. The description of this galaxy will be useful to learn more about this very distant object and to demonstrate new approaches to the study of other “dark” celestial bodies. A recently published study Astrophysical Journal, It will also provide new insights to develop advanced models of galaxy formation and evolution.

Distant, Dark, and Priceless: The Farthest Galaxies

“Very distant galaxies are real sources of information about the past and future evolution of our universe,” explains Marika Giulietti, first author to study astrophysics and cosmology at SISSA. “However, they are very difficult to study. Because they are so compact, they are difficult to observe. We also get very weak light from them due to distance. This darkening is caused by darkening at longer wavelengths that cut off visible light from young stars and make it difficult to detect with optical instruments, and where it can only be observed with powerful interferometers.” It is caused by the dense presence of interstellar dust that emits (sub)millimeter and radio waves”.
These dark objects are not particularly rare: “In recent years,” Giulietti explains, “several distant galaxies have been discovered that are particularly faint and appear completely invisible to even the most powerful optical instruments like the Hubble Space Telescope.”

gravity lens

The tool used in these cases is the so-called gravitational lensing, a solution with great scientific potential. The principle is simple: the general theory of relativity means that cosmic objects that are closer to us and have a large mass distort light from more distant sources that are perfectly aligned with them. “In this way, large celestial bodies act as a kind of giant cosmic lens, making ‘background’ galaxies larger and brighter, allowing them to be identified and studied,” Giulietti continues. Over the past decade, many observational programs have been carried out with this approach. “About a hundred individuals have been identified so far, but there could be many more.”

A truly special object

Giulietti says one of these studies identified the main purpose of the current study: “This was a very special celestial body. It is very bright and potentially lensable, but only at certain precise wavelengths, possibly due to the presence of large amounts of interstellar dust. Therefore, it is very difficult to study. Chile’ Observations made with ALMA, a very modern submillimeter interferometer located in the Atacama Desert in eastern Turkey, allowed us to identify its properties. We searched for this particular object using specific codes that allowed us to both reconstruct the original shape of the background source and understand certain properties of the lens. It provided valuable information about the gas content of the source and we were able to detect how it was dispersed. Our analysis showed that this object is very compact, possibly young, and forming stars at an extremely high rate. In the future, the James Webb Space Telescope will reveal much more about this galaxy than it can currently do. “

Emphasizing the importance of this research, Professor Lapi, co-author of the study, concludes: “Distant galaxies, characterized by young, compact, intense star formation and largely covered by dust and having a very rich reservoir of molecular gas, are the ancestors of the massive dormant galaxies we see in the local Universe and therefore, it provides invaluable information about the processes that led to the formation and evolution of these structures throughout the history of the Cosmos.”

“I would like to emphasize,” the professor continues, “that the success of this work has been achieved thanks to the synergy between SISSA’s Astrophysics and Cosmology Group and the INAF – Institute of Radio Astronomy in Bologna, the ALMA Regional Center in Bologna. Thanks to the collaboration with study co-author Dr. Marcella Massardi, who allowed them to access and learn to use the ALMA data archive, which is a real goldmine for people.”