A massive compact quiescent galaxy at z=2 with a complete Einstein ring in JWST imaging

Understand

One of the surprising results from HST was the discovery that many of the most massive galaxies at z~2 are very compact, having half-light radii of only 1-2 kpc.

• The interpretation is that massive galaxies formed inside-out, with their cores largely in place by z~2 and approximately half of their present-day mass added later through minor mergers.
• Here we present a compact, massive, quiescent galaxy at $z_{\rm phot}=1.94^{+0.13}_{-0.17}$ with a complete Einstein ring.
• The ring was found in the JWST COSMOS-Web survey and is produced by a background galaxy at $z_{\rm phot}=2.98^{+0.42}_{-0.47}$.