News release

From: Springer Nature

JWST data confirms galaxies from long ago (N&V)

The unambiguous confirmation of four galaxies dating to when the Universe was around 300–500 million years old are presented in a pair of papers in Nature Astronomy. The findings are based on images and spectroscopic analysis of data from the James Webb Space Telescope (JWST).

JWST was designed to probe the early Universe and initial surveys have identified many possible candidate galaxies of extremely high redshift, but currently the only way to know that they are at those redshifts is to confirm them spectroscopically: the galaxies have distinctive spectra in ultraviolet light wavelengths, which helps differentiate them from other galaxies that have similar properties. Redshift is a measure of the speed and can help infer distance: due to the expansion of the Universe, light from distant objects shifts to wavelengths towards the red end of the spectrum — the redder the image, the more distant the object is. Understanding what happened during the formation of the earliest galaxies is important for understanding the conditions and processes that led to the formation of the first stars.

Brant Robertson, Sandro Tacchella and colleagues analysed images from JWST’s near-infrared camera. They identified four galaxies (JADES-GS-z10-0, JADES-GS-z11-0, JADES-GS-z12-0, JADES-GS-z13-0) in the redshift range of 10.3 to 13.2. JADES-GS-10-0 and JADES-GS-11-0 were known previously from Hubble imaging, while JADES-GS-z12-0 and JADES-GS-z13-0 were newly discovered. They determined their star-formation rates, sizes and other properties indicating that each galaxy could contain 100 million solar masses in stars, in stellar populations that are less than one hundred million years old based on their cosmic age. The authors infer that the moderate levels of star formation and their compact size suggest higher star formation rate surface densities, which are a key indicator of how the galaxies formed. They suggest the galaxies formed rapidly with intense internal radiation fields.

In the companion paper, Emma Curtis-Lake, Stefano Carniani and colleagues used JWST’s near-infrared spectrometry instrument to provide the first spectroscopic confirmations of galaxies (JADES-GS-z12-0 and JADES-GS-z13-0) further away than those identified by the Hubble space telescope, as well as confirming the two objects originally detected with Hubble (JADES-GS-10-0 and JADES-GS-11-0 ) to be inhabiting the Universe when it was less than 350 million years old, with measured redshifts of 10.3 to 13.2.  The spectra do not show fingerprints of complex elements like carbon, oxygen and nitrogen, indicating that the stars have not yet processed the pristine hydrogen and helium left over from the Big Bang to produce large stores of these heavier elements in the galaxies. The authors suggest that their findings demonstrate the rapid emergence of the first generations of galaxies.