Astronomers reported the discovery of a new galaxy using the James Webb Space Telescope (JWST) as part of the JWST COSMOS-Web survey. The newly discovered object, called JWST-ER1, is a massive and compact dormant galaxy. The findings were detailed in a paper published on the preprint server on September 14. arXiv.

Massive galaxies that have stopped forming stars (known as dormant galaxies) are the likely ancestors of giant elliptical galaxies. Given that these objects form stars earlier and accumulate stellar mass more quickly, they may be key to improving our understanding of the galaxy’s evolutionary process.

Now, a team of astronomers led by Peter van Dokkum of Yale University has reported the discovery of a new such galaxy, called JWST-ER1. The object was identified using JWST’s Near Infrared Camera (NIRCam) as part of an ongoing, deep survey of up to 1 million galaxies known as COSMOS-Web. One of the most notable features of JWST-ER1 is the so-called Einstein ring, a phenomenon in which light appears as a ring due to gravitational lensing.

“The galaxy and its ring were identified during JWST NIRCam observations within the COSMOS-Web project, a large publicly available survey using filters F115W, F150W, F277W and F444W,” the researchers said.

NIRCam observations show that JWST-ER1 consists of an early-type compact galaxy (JWST-ER1g) and a complete Einstein ring (JWST-ER1r) with two distinct red concentrations. The measured diameter of the center of the ring was approximately 1.54 arcseconds.

The new galaxy was found at a redshift of 1.94, has a radius of approximately 21,500 light-years and an estimated mass of 650 billion solar masses. The results indicate an age of 1.9 billion years and a star formation rate as low as four solar masses per year. Therefore, JWST-ER1 is a large and dormant galaxy. It is also quite compact, like other stationary galaxies with similar redshifts.

As for JWST-ER1r’s ring, astronomers found that it consists of a background galaxy with a photometric redshift of 2.98. It unites a large number of known Einstein rings, although most are incomplete. The study also found that JWST-ER1 is nearly perfectly round, with no obvious star-forming regions, tidal tails or other irregularities in the NIRCam image.

The authors of the paper recommend further observations of JWST-ER1 to investigate whether nearby galaxies or line-of-sight structures contribute to its mass and to test whether JWST-ER1 is the central progenitor galaxy of the cluster. Source