JWST discovers massive and compact quiescent galaxy

As part of the JWST COSMOS-Web survey, astronomers have announced the finding of a new galaxy with the James Webb Space Telescope (JWST). JWST-ER1, the newly discovered object, is a large, compact, inactive galaxy. A article summarizing the results was posted on the pre-print service arXiv on September 14.

Giant elliptical galaxies may have originated from large quiescent galaxies, which are galaxies with a mass that has ceased to generate stars. These objects may be essential to advancing our knowledge of the history of galaxies since they generated stars sooner and accumulated their stellar masses faster.

A group of astronomers from Yale University, led by Pieter van Dokkum, has now reported the discovery of a new galaxy of this kind, designated JWST-ER1. The Near Infrared Camera (NIRCam) on JWST was used to identify the object as part of the ongoing COSMOS-Web, a large and deep survey of up to a million galaxies. The "Einstein ring," a phenomena caused by gravitational lensing that causes light to look as a ring, is one of JWST-ER1's most notable characteristics.

"In the framework of the COSMOS-Web project, a public wide-area survey using the F115W, F150W, F277W, and F444W filters, the galaxy and its ring were identified in JWST NIRCam observations," the researchers said.

JWST-ER1 is made up of a full Einstein ring (JWST-ER1r) with two prominent red concentrations and a compact early-type galaxy (JWST-ER1g), according to NIRCam data. It was determined that the ring's center had a diameter of around 1.54 arcseconds.

The new galaxy was discovered at 1.94 redshift, with a mass estimated at 650 billion solar masses and a radius of around 21,500 light years. The findings indicate a low star-formation rate of four solar masses per year and an age of 1.9 billion years. JWST-ER1 is a huge, inactive galaxy as a result. In line with other inactive galaxies at comparable redshifts, it is likewise rather compact.

Regarding the ring JWST-ER1r, the scientists discovered that it originates from a background galaxy located at a photometric redshift of 2.98. Though most of the known Einstein rings are incomplete, it unites a huge number of them.

Additionally, the study discovered that JWST-ER1 is nearly perfectly spherical and that the NIRCam imagery does not show any clear star-forming areas, tidal tails, or other anomalies.

In order to determine if JWST-ER1 is the center galaxy of a cluster progenitor or whether surrounding galaxies or structures along the line of sight might contribute to its mass, the authors of the research suggest doing more observations of JWST-ER1.