Webb Telescope reveals a galaxy that shouldn’t exist

Astronomers have discovered an isolated dwarf galaxy without star formation, which appears in James Webb Space Telescope images and was not the main object of observation.

Galaxies are held together by gravity and made up of stars and planets, giant clouds of dust and gas, as well as dark matter. Dwarf galaxies are the most abundant in the universe and are, by definition, smaller and less luminous. They have less than 100 million stars, whereas the Milky Way, for example, has about 200 billion stars.

The recent dwarf galaxy observation of an abundance of “ultradiffuse galaxies” beyond the scope of previous large spectroscopic surveys suggests that our understanding of dwarf galaxy populations may be incomplete.

In the new study, a team led by Tim Carlton, assistant research scientist at Arizona State University, was initially observing a galaxy cluster as part of the JWST Prime Extragalactic Area for Reionization and Lensing Science (PEARLS) project.

The dwarf galaxy, PEARLSDG, appeared in some of the team’s JWST images. It was not a target at all, a short distance away from the main observing area, in a region of space where they did not expect to see anything.

Their results have been published in the Astrophysical Journal Letters.

PEARLSDG did not have the typical features of a dwarf galaxy that one would expect to see. It does not interact with nearby galaxies, but it also does not form new stars. It turns out that this is an interesting case of an isolated inactive galaxy.

“Except in relatively few cases, isolated, inactive dwarf galaxies of this type have never been observed before. In fact, given our current understanding of galaxy evolution, they are not expected to exist, so the fact that we observed this object See, helps us improve our theories about galaxy formation,” Carleton said in a statement. “In general, dwarf galaxies that exist alone continue to form new stars.”

Until now, astronomers’ understanding of galaxy evolution reflected an isolated galaxy that continued to form young stars or would interact with a more massive companion galaxy. This theory does not apply to PEARLSDG, which appears to be an ancient stellar population that does not form new stars and remains latent.

As an added surprise, individual stars can be seen in the team’s JWST images. These stars are brightest at JWST wavelengths; This is one of the most distant galaxies in which we can see these stars with this level of detail. The brightness of these stars allows astronomers to measure their distance: 98 million light years.

For this study, Carleton and team used image data from JWST’s near-infrared camera (NIRCam); Spectroscopic data from the Deveney Optical Spectrograph at the Lowell Discovery Telescope in Flagstaff, Arizona; Archival images from NASA’s Galax and Spitzer space telescopes; and ground images from the Sloan Digital Sky Survey and the Dark Energy Camera Legacy Survey.