The James Webb Space Telescope has observed a gravitationally lensed galaxy from 510 million years after the Big Bang, revealing insights into the early Universe’s reionization process and the characteristics of the earliest galaxies.
New James Webb Space Telescope (JWST) imaging and spectroscopy observations have revealed a gravitationally lensed galaxy, with strong nebular emission lines, at redshift 9.5 – corresponding to 510 million years after the Big Bang.
Though little is known about galaxies at such early times, emission lines in the spectrum of this distant galaxy allowed the study’s authors to determine some of its physical properties. It is thought that the Universe was once opaque, dominated by dense neutral hydrogen filling intergalactic space.
Light from the earliest galaxies gradually reionized the majority of the gas in the intergalactic medium, transforming the Universe and making it transparent. However, the precise timeline of reionization and the relative contributions of the Universe’s earliest galaxies to this process remain uncertain.
Hayley Williams and colleagues report near-infrared imaging and spectroscopy observations, from JWST, of a distant galaxy magnified by gravitational lensing. The observed galaxy is located at redshift 9.5, corresponding to about 510 million years after the Big Bang and before reionization was complete. The high magnification provided by gravitational lensing enabled the authors to detect the intrinsically faint galaxy and to obtain spectral information with strong nebular emission lines that reveal some of the galaxy’s physical properties.
According to Williams et al., the findings show that the galaxy has a radius of 16.2 parsecs and is much more compact than other galaxies with equivalent luminosity, suggesting a high density of star formation. What’s more, spectrographic analysis shows that the galaxy has an abundance of oxygen and hydrogen.
Reference: “A magnified compact galaxy at redshift 9.51 with strong nebular emission lines” 13 April 2023, Science.
The research was supported by the National Science Foundation and NASA through the Space Telescope Science Institute, with additional funding from the United States-Israel Binational Science Foundation and the Spanish State Research Agency.