The discovery of a dwarf galaxy, named PEARLSDG, by a team of astronomers led by Tim Carleton from Arizona State University, challenges our understanding of galaxy evolution. Observed through the James Webb Space Telescope (JWST), this galaxy is characterized by its lack of star formation and isolation, thus defying current theories.
Dwarf galaxies, often defined by their small size and low brightness, are among the most abundant objects in the universe. However, PEARLSDG presents unexpected characteristics for a galaxy of its type: it does not create new stars and does not appear to interact with other nearby galaxies. This profile is atypical for a dwarf galaxy, which, when isolated, usually continues to form young stars.
PEARLSDG is identified in cyan, and the green squares show the area covered by the NIRCam imagery. Two of the closest massive galaxies (in projection) are identified by red circles.
Credit: The Astrophysical Journal Letters (2024).
The discovery was made as part of the JWST Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) project, although PEARLSDG was not the main target of the observations. It was the analysis of the images taken by the JWST's Near-InfraRed Camera (NIRCam) that revealed this distant dwarf galaxy. NIRCam's high resolution and sensitivity made it possible to identify individual stars within PEARLSDG, thus providing valuable information on the galaxy's distance, estimated at 98 million light-years.
The absence of recent star formation signatures, typical of new stars, along with the spectrometric analysis carried out with the DeVeney spectrograph on the Lowell Discovery Telescope in Flagstaff, Arizona, confirm the stasis state of PEARLSDG. These observations are complemented by archive data in ultraviolet, optical, and infrared, notably from the Galex and Spitzer space telescopes, as well as from the Sloan Digital Sky Survey and the Dark Energy Camera Legacy Survey.
This discovery challenges the current understanding of galaxy evolution, suggesting the existence of other isolated and quiescent dwarf galaxies yet to be discovered. The JWST, with its advanced instruments, plays a key role in this quest, opening new perspectives on the formation and evolution of galaxies in the universe.