An article published in “The Astrophysical Journal Letters” reports the results of the study of three very compact primordial galaxies with characteristics that can’t be explained by current cosmological models. A team led by researchers from Penn State University used observations conducted with the James Webb Space Telescope within the RUBIES survey to examine three objects that were considered mysterious for their strange characteristics.
In an article published in the journal “Nature” the researchers had already proposed that those were galaxies, and the new examination of the data confirms that. We see them as they were when the universe was between 600 and 800 million years old but their emissions indicate that they contain stars that are already relatively old and supermassive black holes with masses that were already enormous, perhaps more than the one at the center of the Milky Way.
Current models of the formation of galaxies and supermassive black holes seemed to offer descriptions that matched observations obtained in the early universe. However, the data currently available about three objects observed during the RUBIES survey makes them unexplainable by those models.
The data is collected by the James Webb Space Telescope using the NIRSpec instrument to observe several thousand sources selected from images captured with the NIRCam. The data about the objects cataloged as RUBIES-EGS-49140, RUBIES-EGS-55604/L23-38094, and RUBIES-EGS-966323/L23-14924 was examined leading first to the study published in “Nature” and then to the one published in “The Astrophysical Journal Letters” that confirms that they are primordial galaxies.
In galaxies we see as they were between 600 and 800 million years after the Big Bang, astronomers would expect to find young stars and supermassive black holes in their growth phase. They are extremely compact galaxies, and that’s already unusual given that their volume is about a thousandth of the Milky Way’s. Spectroscopic data analysis reveals elements in their stars that indicate some of them are hundreds of millions of years old, much older than expected. Their supermassive black holes have grown much larger than model predictions.
One problem in observing these three early galaxies is figuring out how much of their light is emitted by stars and how much by supermassive black holes. This means they could be massive galaxies that formed earlier than current models predict, or galaxies with normal stellar masses with supermassive black holes that are already truly colossal. Galaxies and their supermassive black holes are supposed to experience a common evolution, but in the early galaxies studied in this study, they appear to be evolving separately.
The researchers would like to conduct follow-up observations to observe the three galaxies for longer periods. This could provide more data with the possibility of examining their spectral characteristics to obtain more precise information on the traces left by the various elements of the stars in the electromagnetic emissions. It would also be easier to understand which are the stellar emissions and which are from the supermassive black holes.
Only more precise data on these three primordial galaxies will allow to understand whether they can be explained in some way by current models of galaxy formation or these models are still too limited. For now, the James Webb Space Telescope continues to lead to surprising discoveries, starting new astronomical studies that could give very interesting results in the coming years.
