An article published in “The Astrophysical Journal” reports the characterization of the galaxy HATLASJ113526.2-01460, or simply J1135, which we see as it was about two billion years after the Big Bang. So far, the problem was actually being able to resolve their characteristics and now a team led by Professor Andrea Lapi used observations conducted with the ALMA radio telescope to obtain this result. ALMA’s power and sensitivity made it possible to detect even the very weak radio and submillimeter emissions, which might be the only ones that reach us from J1135 due to the considerable presence of interstellar dust within it. These observations help to better understand the formation and evolution of galaxies in the young universe.
Marika Giulietti, the first author of the article, who is studying for her Ph.D. in astrophysics and cosmology at the International School for Advanced Studies in Trieste, Italy, explained that very distant galaxies are real mines of information about the past and future evolution of our universe but are difficult to observe due to the large amount of interstellar dust inside them. Even the most powerful instruments can’t detect this type of galaxy at optical and infrared frequencies, therefore very powerful radio telescopes are needed to be able to observe them. ALMA (Atacama Large Millimeter/submillimeter Array) made it possible to observe one.
Gravitational lenses are useful in astronomical research about distant objects because the gravity of a galaxy or galaxy cluster can distort light from sources that are behind them from Earth’s perspective, resulting in them being magnified. The galaxy J1135 can be observed thanks to a gravitational lens but the light arriving on Earth is still very weak and maybe limited to the radio and submillimeter bands. Due to the distortion, it’s necessary to apply specially created algorithms to the detected images to reconstruct the original images.
The image (Courtesy M. Giulietti et al, ApJ, 2023. All rights reserved) shows the results of some reconstructions of J1135’s shape obtained starting from the detections conducted with the ALMA radio telescope in different electromagnetic frequencies.
The difficulties in observing the galaxy J1135 even with powerful radio telescopes led to discussions about its nature. The observations conducted with the ALMA radio telescope show a young and compact galaxy in which the rate of star formation was estimated at a thousand times that of the Milky Way. These features indicate a progenitor galaxy of the massive and quiescent galaxies present in the so-called local universe. In essence, understanding the characteristics of galaxies like J1135 is useful for reconstructing the early stages of a history that leads them to become like some relatively close galaxies that we can study in depth.
In recent years, several galaxies strongly obscured by dust were discovered. Their weak emissions make them difficult to study, and this study of J1135 represents a step forward. Every successful observation of such a galaxy offers new insights, and the one achieved with J1135 once again proves the possibilities offered by ALMA almost 10 years after its official inauguration.
The James Webb Space Telescope is sensitive to mid-infrared and could detect some emissions from the galaxy J1135 passing through the dust inside it. For astronomers, it would be another step forward in understanding its characteristics, also through a mapping of the distribution of interstellar dust. This would offer new insights into the formation and evolution of galaxies in the young universe.
