Stress testing ΛCDM with high-redshift galaxy candidates

Early data from the James Webb Space Telescope ( JWST) have revealed a bevy of high-redshift galaxy candidates with unexpectedly high stellar masses. An immediate concern is the consistency of these candidates with galaxy formation in the standard.CDM cosmological model, wherein the stellar mass (M-star) of a galaxy is limited by the available baryonic reservoir of its host dark matter halo. The mass function of dark matter haloes therefore imposes an absolute upper limit on the number density n (>M-star, z) and stellar mass density p(star) (>M-star, z) of galaxies more massive than M-star at any epoch z. Here I show that the most massive galaxy candidates in JWST observations at z approximate to 7-10 lie at the very edge of these limits, indicating an important unresolved issue with the properties of galaxies derived from the observations, how galaxies form at early times in.CDM or within this standard cosmology itself.

Automated summary

Early data from the James Webb Space Telescope (JWST) show that high-redshift galaxy candidates have unexpectedly high stellar masses, posing a concern regarding their consistency with the standard CDM cosmological model. The mass function of dark matter haloes limits the number and stellar mass density of galaxies more massive than a certain stellar mass at any epoch, and the most massive galaxy candidates at z approximately 7-10 observed by JWST push the limits, indicating unresolved issues with galaxy properties derived from observations and the formation of galaxies in the CDM model or within the standard cosmology itself.