Two articles, available here and here (link to the file in PDF format), that have yet to pass the peer-review phase report some results of observations of primordial galaxies conducted with the James Webb Space Telescope within the JWST Advanced Deep Extragalactic Survey (JADES) program which has precisely the aim of studying the oldest and faintest galaxies. A team of astronomers used Webb’s NIRCam and NIRSpec instruments to determine the distances of four galaxies we see as they were less than 400 million years after the Big Bang using a spectroscopic analysis of their light.
Years before the James Webb Space Telescope was launched, the instrument development teams started defining some survey programs. In 2015, the JADES program was proposed to allocate a little more than a month of Webb’s time over the course of two years for a survey of the early universe.
Going even further back in time is one of this telescope’s goals. In the case of primordial galaxies already studied with other instruments, the aim is to obtain more information with more details. Spectroscopic information offers reliable measurements on the distances of galaxies and now the first results obtained with the James Webb Space Telescope are arriving.
In this case, four primordial galaxies were studied. The image (NASA, ESA, CSA, M. Zamani (ESA/Webb), Leah Hustak (STScI), Brant Robertson (UC Santa Cruz), S. Tacchella (Cambridge), E. Curtis-Lake (UOH), S Carniani (Scuola Normale Superiore), JADES Collaboration) shows an area of the Hubble Space Telescope’s Ultra Deep Field on which the study was focused. Webb’s NIRCam instrument made it possible to conduct observations in nine different infrared wavelength ranges. The NIRSpec instrument made it possible to precisely measure the redshift of the galaxies (at right).
Two of the observed galaxies were already studied with Hubble and Webb confirmed the measurements of their distances. The other two are the most distant galaxies observed so far with spectroscopic confirmation. Webb saw the most distant galaxy as it was about 13.5 billion years ago, a result obtained thanks to this space telescope.
Obtaining information about these primordial galaxies is important for reconstructing the details of the formation of the first galaxies and their consequences. For example, according to the researchers, they contributed to reionization, the process in which hydrogen, which was neutral in the early period of the universe life, was separated into protons and electrons. This was a crucial moment because neutral hydrogen blocked light, so reionization transformed the universe from a dark place to one illuminated by the light of primordial stars.
The JADES program will continue in 2023 with another study of another area and then return again to the one containing the galaxies covered by this study. The articles already written will be evaluated and perhaps improved, and we can expect more that will help understand how the universe came to be as we know it today.
