A team of astronomers discovers a galaxy that shouldn’t exist

A team of astronomers discovers a galaxy that shouldn’t exist

This article has been reviewed in accordance with Science

Fact check

trusted source

Proofreading


Color composite image of PEARLSDG made using JWST NIRCAM data. Individual stars appear as small points of light in the image. Its somewhat dull color and lack of many bright stars are consistent with its advanced age and lack of continued star formation. Image credit: NASA, ESA, CSA, Jake Summers (ASU), Jordan CJ D’Silva (UWA), Anton M. Koekemoer (STScI), Aaron Robotham (UWA) and Rogier Windhorst (ASU).

× Close


Color composite image of PEARLSDG made using JWST NIRCAM data. Individual stars appear as small points of light in the image. Its somewhat dull color and lack of many bright stars are consistent with its advanced age and lack of continued star formation. Image credit: NASA, ESA, CSA, Jake Summers (ASU), Jordan CJ D’Silva (UWA), Anton M. Koekemoer (STScI), Aaron Robotham (UWA) and Rogier Windhorst (ASU).

A team of astronomers, led by Arizona State University associate research scientist Tim Carleton, has discovered a dwarf galaxy that appeared in the James Webb Space Telescope’s imaging and was not the primary observing target.

Galaxies are bound together by gravity and are composed of stars and planets, with huge clouds of dust and gas as well as dark matter. Dwarf galaxies are the most abundant galaxies in the universe, and by definition they are small and have low luminosity. It contains fewer than 100 million stars, while the Milky Way, for example, has nearly 200 billion stars.

Recent dwarf galaxy observations of an abundance of “ultra-diffusive galaxies” that exceed the range of previous large spectroscopic surveys suggest that our understanding of dwarf galaxy populations may be incomplete.

In a newly published study, Carleton and his team initially looked at a group of galaxies as part of the JWST Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) project.

The dwarf galaxy, PEARLSDG, is featured in some of the team’s JWST images. It wasn’t the target at all, it was just a little bit away from the main field of observation, in a region of space where they didn’t expect to see anything.

Their results have been published in Astrophysical Journal Letters.

PEARLSDG did not have the usual characteristics of a dwarf galaxy one would expect to see. It’s not interacting with a nearby galaxy, but it’s not forming new stars either. As it turns out, it’s an interesting case of a quiet, isolated galaxy.

“These types of isolated, quiet dwarf galaxies have never been seen before with relatively few exceptions. They’re not really expected to exist given our current understanding of galaxy evolution, so the fact that we’re seeing this object helps us improve our theories about galaxy formation,” Carlton said. “Generally, dwarf galaxies that exist on their own continue to form new stars.”

Until now, astronomers’ understanding of galaxy evolution has shown either an isolated galaxy that continues to form young stars or that will interact with a more massive companion galaxy. This theory does not apply to PEARLSDG, which appears as an old star cluster, does not form new stars, and maintains itself.

In another surprise, individual stars can be observed in the JWST images taken by the team. These stars are brightest at JWST wavelengths; It is one of the farthest galaxies where we can see these stars at this level of detail. The brightness of these stars allows astronomers to measure their distance from Earth, which is 98 million light-years.


Top: JWST of the PEARLSDG Galaxy (blue = F090W + F150W, green = F200W + 0.5 x F277W, red = 0.5 x F277W + F356W + F444W). Bottom: DECALS grz image of the sky immediately surrounding PEARLSDG. Both images are aligned so that north is up and east is left. The PEARLSDG is identified by the cyan box, and the green boxes show the area covered by the NIRCam imaging. Two nearby massive galaxies (within the projection) are also visible (marked in red circles). credit: Astrophysical Journal Letters (2024). doi: 10.3847/2041-8213/ad1b56

× Close


Top: JWST of the PEARLSDG Galaxy (blue = F090W + F150W, green = F200W + 0.5 x F277W, red = 0.5 x F277W + F356W + F444W). Bottom: DECALS grz image of the sky immediately surrounding PEARLSDG. Both images are aligned so that north is up and east is left. The PEARLSDG is identified by the cyan box, and the green boxes show the area covered by the NIRCam imaging. Two nearby massive galaxies (within the projection) are also visible (marked in red circles). credit: Astrophysical Journal Letters (2024). doi: 10.3847/2041-8213/ad1b56

In this study, Carleton, an assistant research scientist at the BIUS Center for Cosmic Foundations at Arizona State University’s College of Earth and Space Exploration, and his team used a wide range of data.

This includes imaging data from JWST’s Near Infrared Camera (NIRCam); Spectroscopic data from the DeVeney Optical Spectrograph on the Lowell Discovery Telescope in Flagstaff, Arizona; Archival photography from NASA’s GALEX and Spitzer space telescopes; And ground-based imaging from the Sloan Digital Sky Survey and Dark Energy Camera Legacy Survey.

more information:
Timothy Carleton et al., PERLZ: A possible isolated quiescent dwarf galaxy with a tip of a red giant branch at 30 megaparsecs, Astrophysical Journal Letters (2024). doi: 10.3847/2041-8213/ad1b56

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *