Astronomers have seen the building blocks of galaxies in such detail for the first time, looking back to an era when the Universe was only a billion years old. A large ALMA program called CRISTAL has studied cold gas, dust, and star clusters in 39 typical galaxies where stars are forming intensively, revealing the mechanisms of their formation.
Interpretation of invisible structures
“Thanks to ALMA’s unique sensitivity and resolution, we can resolve the internal structure of these early galaxies in ways never possible before,” emphasizes CRISTAL research leader Rodrigo Herrera-Camus. The team used specific ionized carbon ([CII]) emission, which serves as a marker for cold interstellar gas and dust. By combining these ALMA data with infrared images from the James Webb and Hubble telescopes, scientists have created detailed maps of the interstellar environment of each galaxy.
A study published in Astronomy & Astrophysics revealed several important patterns. Most galaxies showed star formation in giant clusters thousands of light-years in size, demonstrating how star-forming regions are formed. Some galaxies already showed signs of rotation — early disc-like structures, the embryos of future spiral galaxies. The [CII] emission often extended far beyond the visible stars, indicating the presence of huge reservoirs of cold gas suitable for future star formation or escaping through stellar winds.
The project proved that ALMA is capable of revealing the internal structure and dynamics of galaxies even in the very distant past, demonstrating their evolution and star formation processes.
Two mysterious galaxies
Two galaxies from the CRISTAL project turned out to be particularly unusual. In CRISTAL-13, massive dust clouds completely obscure the visible light of newborn stars. Only ALMA, observing in the millimeter range, was able to “see” through this veil and reveal the hidden structures.
CRISTAL-10 proved to be even more mysterious: its [CII] emission is abnormally weak compared to its infrared brightness. This rare feature, found only in extremely eclipsed galaxies (such as neighboring Arp 220), indicates extreme conditions or an unusual source of energy within it.
A new window into the Universe’s past
The CRISTAL study significantly deepens our understanding of the formation of the first galaxies and stars. It provides an unprecedented view of the distribution of cold gas — the fuel for star formation — and reveals the diversity of structural components that ultimately led to the formation of the galaxies we see today. ALMA continues to be a key instrument for studying the earliest stages of cosmic history.
We previously reported on how ALMA discovered an exoplanet forming moons.
According to phys.org
