Italian researchers participated in the discovery of a distant galaxy at the edges of the Universe
An international research team led by researcher Austin Hoag, University of California, which included Laura Pentericci, an astronomer at the National Institute for Astrophysics (INAF) in Rome, together with Italian researchers Tommaso Treu, University of California-Los Angeles, and Michele Trenti, University of Melbourne in Australia, has discovered a small and faint galaxy at the very edges of the Universe.
Macs1423-z7p64, this is the name of the newly discovered galaxy, is similar to many other known galaxies in the Universe. What makes it special is its vast distance, in space and time: the light of this celestial body travelled for 13.1 billion years before reaching us and it was emitted when the Universe was a little more than 500 million years old, less than four percent of its current age.
“Other most distant objects are extremely bright and probably rare compared to other galaxies”, said Austin Hoag, lead author of the paper on the discovery, published online in Nature Astronomy. “We think this is much more representative of galaxies of the time”.
These ultra-distant galaxies from the early Universe are of great interest to astronomers since they date back to the so-called Epoch of Reionization, a period that occurred approximately between three hundred thousand and one billion years after the Big Bang, during which the Universe became “transparent”, making visible the light of the first stars and galaxies.
According to the Big Bang theory, reionization refers to the time when the huge mass of neutral hydrogen, which blocks radiation, melted away allowing light to filter and the first celestial bodies, which formed from the condensation of that primordial material, to become visible, converting neutral hydrogen into ionized hydrogen, allowing the free propagation of electromagnetic radiation. However, a lot remains to be understood about what happened at that distant epoch. “We have a before and an after, but not exactly a when”, continued Hoag.
There are also doubts as to which celestial objects made the reionization process possible, that is, whether it was the young galaxies or whether black holes and gamma-ray bursts contributed to the process.
“At the moment, the main ‘suspects’ are galaxies”, said Laura Pentericci, an INAF astronomer at the Astronomical Observatory in Rome. “In particular, we think that most ionizing photons come from the faintest galaxies, such as the one we have identified in this study. Unfortunately, they are the most difficult to detect just because of their low luminosity. In this particular case, we were able to detect it only because the massive cluster of galaxies situated between us and the galaxy acted as a magnifying glass, magnifying its brightness”.
The discovery of Macs1423-z7p64 was made possible by the gravitational lensing effect exerted by a cluster of galaxies that lies between us and the distant galaxy, which magnified the galaxy’s brightness tenfold and made it visible using the Hubble space telescope. The team was able to determine the distance of the galaxy by analyzing its light with the MOSFIRE spectrograph installed at the Keck I telescope on the Hawaii Islands.