An article accepted for publication in “The Astrophysical Journal” reports the results of a study of the structure and morphology of galaxies that existed in the first three billion years of life of the universe. A team of researchers used observations conducted with the James Webb Space Telescope as part of the CEERS survey to obtain enough detail to understand what primordial galaxies were like. The conclusion is a confirmation of previous research regarding the remarkable variety of shapes and structures and turned out even superior thanks to Webb. In many of them, the structures are already quite evolved, as in closer and younger galaxies.
Studies on the origin and evolution of galaxies have been enriched with every advance in astronomical instruments. The James Webb Space Telescope was designed with this among its main purposes. In recent years, the Hubble Space Telescope was used to create a census of primordial galaxies that already showed their diversity of shapes and structures. In the first months of its scientific mission, Webb made it possible to take a step forward.
850 galaxies with an age between about 11 and 13 billion years were observed with the James Webb Space Telescope within the Cosmic Evolution Early Release Science (CEERS) survey. Its instruments made it possible to capture much more detail than Hubble and therefore to recognize the different types of galaxies with greater precision.
The top image (NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/Z. Levay; Cutout images: NASA/STScI/CEERS/TACC/S. Finkelstein/M) shows a mosaic of 690 frames obtained with Webb’s Near Infrared Camera (NIRCam) instrument which constitutes one of the first images of the CEERS survey and shows in the insets some examples of primordial galaxies.
An example of types of galaxies is given by the ones in which the Hubble Space Telescope detected a disk. The new observations conducted with the James Webb Space Telescope have also made it possible to discover many galaxies with structures such as spheroids and irregular shapes of the types observed at shorter distances and therefore younger.
In essence, Webb made it possible to discover the diversity of primordial galaxies and that many of them were already evolved when they were young. In the end, 488 of the 850 galaxies previously studied with Hubble were reclassified as new details about their structures were discovered.
The bottom image (Courtesy Jeyhan S. Kartaltepe et al., Apjl, 2023) shows a selection of images captured by the James Webb Space Telescope’s NIRCam instrument with the various morphological categories to which different galaxies belong with an age between 11 and 13 billion years.
The results obtained thanks to the CEERS survey are in line with cosmological simulations such as IllustrisTNG. Observations and simulations indicate that galaxies with disks and spheroids already exist among the oldest ones and that the shape of galaxies has an evolution over time becoming more regular.
While the researchers were analyzing the images captured by the James Webb Space Telescope, the CEERS survey continued. There is now an archive that potentially offers images of thousands of primordial galaxies. Images being collected in another investigation called COSMOS-Web will also be added later in 2023, with lead investigator Professor Jeyhan Kartaltepe of the Rochester Institute of Technology, co-investigator of the CEERS survey and first author of this study. For this reason, the scientist stated that this is only the beginning and that the incoming data will make it possible to collect much larger samples of galaxies, especially the oldest.
