A distant celestial body in a young Universe one-sixth its size. Even advanced equipment cannot see a dark thing. The SISSA research group led by Prof. Andrea Lapi which studies galaxy formation and evolution has finally identified its primary features using ALMA interferometer scans. It’s a young galaxy with plenty of interstellar dust that forms stars 1000 times faster than the Milky Way. The description of this galaxy will disclose more about this faraway object and suggest new ways to investigate other “dark” celestial entities. The Astrophysical Journal study will also help create enhanced galaxy formation and evolution models.

The furthest galaxies are dark and valuable.

The first author, SISSA Astrophysics and Cosmology student Marika Giulietti says, “Very distant galaxies are true mines of knowledge regarding the past and future history of our Universe.” Studying them is difficult. Compact and hard to see. Distance also reduces their luminosity. The enormous quantity of interstellar dust intercepts visible light from newborn stars, making it impossible to detect with optical detectors, and re-emits it at higher wavelengths where it can be seen only with strong interferometers in the (sub-)millimetre and radio wavebands.”

According to Giulietti, “several distant galaxies have been identified that are extremely veiled, looking entirely invisible even to the most powerful optical instruments, such as the Hubble Space Telescope.”

Gravity lensing

Gravitational lensing, a promising scientific tool, is applied here. General relativity states that massive space objects closer to us bend light from distant sources that are perfectly aligned. “In this approach, massive celestial entities operate as a type of giant cosmic lens that makes the ‘background’ galaxies look larger and brighter, allowing them to be discovered and studied,” Giulietti said. Several observation programs have used this strategy in the past decade. “About 100 have been discovered, but there might be many more.”

Unique item

Giulietti explains, “This was a really rare heavenly body. Due to high amounts of interstellar dust, it is brilliant and lensable at certain wavelengths. It’s complicated to study. We determined its characteristics using ALMA, a sophisticated sub-millimetre interferometer in Chile’s Atacama desert. We used programs to rebuild the background source and comprehend the lens’s features. The observations revealed this source’s gas content and distribution. This compact, youthful object is producing stars at a very fast pace, according to our study. Only the James Webb Space Telescope can disclose more about this galaxy in the future.”

“Distant galaxies that are young, compact, characterised by vigorous star formation, and largely obscured by dust, and that possess a very rich reservoir of molecular gas, are forerunners of the massive quiescent galaxies that we see in the local Universe, and therefore provide very valuable insights into the processes leading to the formation and evolution of these structures dur

“I would like to emphasise that the success of this research was achieved through synergy between the SISSA Astrophysics and Cosmology group and the ALMA Regional Centre based at the INAF – Institute of Radio Astronomy in Bologna (in particular through collaboration with Dr. Marcella Massardi, co-author of the study), which allowed our students to access, and learn how to use effectively, the ALMA data archive, a real gold mine for astrophysics,” says the professor

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