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Dark Mysteries of the Cosmos: Unraveling the Secrets of an Invisible Galaxy

Galaxy Astrophysics Mystery Concept Art

Researchers from SISSA have identified the main properties of a mysterious, distant celestial object using the ALMA interferometer. The young, compact galaxy is forming stars 1000 times faster than the Milky Way, and the study offers valuable insights into galaxy formation and the study of other “dark” celestial bodies.

A mysterious and very distant object, in a universe as it was ‘just’ two billion years after the

Lensed Galaxy Acquired With ALMA Interferometer

Image of the lensed galaxy acquired with the ALMA interferometer Credit: Giulietti et al.

Remote, dark and invaluable: the most distant galaxies

“Very distant galaxies are real mines of information about the past and future evolution of our Universe,” explains the first author Marika Giulietti, who studies Astrophysics and Cosmology at SISSA. “However, studying them is very challenging. They are very compact and therefore difficult to observe. Also, because of distance, we receive very weak light from them. The cause of this obscuration is the massive presence of interstellar dust, which intercepts visible light from young stars, and makes it difficult to detect with optical instruments, and re-emits it at greater wavelengths where it can be observed only with powerful interferometers in the (sub-)millimetre and radio wavebands.”
These dark bodies are not particularly rare: “In recent years” explains Giulietti “several distant galaxies have been discovered that are particularly obscured, appearing completely invisible even to the most powerful optical instruments, such as the

A truly special object

It was in one of these investigations, says Giulietti, that the main object of this current study was identified: “This was a very special celestial body. It is very bright and potentially subject to lensing, but this occurs only at certain precise wavelengths, probably due to the presence of large quantities of interstellar dust. Studying it is consequently very complex. Observations made with ALMA, a very modern sub-millimetre interferometer located in the Atacama desert of Chile, enabled us to determine its features. We studied this peculiar object by adopting particular codes that enabled us to reconstruct the original shape of the background source and also to understand certain properties of the lens itself. The observations also provided valuable information about the gas content of this source, and we were able to determine how it is distributed. Our analysis showed that this object is very compact, presumably young, and forming stars at an extremely high rate. In the future, the DOI: 10.3847/1538-4357/aca53f

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