On the Significance of Rare Objects at High Redshift: The Impact of Cosmic Variance

Understand

The discovery of extremely luminous galaxies at ultra-high redshifts ($z\gtrsim 8$) has challenged galaxy formation models.

• Most analyses of this tension have not accounted for the variance due to field-to-field clustering, which causes the number counts of galaxies to vary greatly in excess of Poisson noise.
• This super-Poissonian variance is often referred to as cosmic variance.
• Since cosmic variance increases rapidly as a function of mass, redshift, and smaller observing areas, the most massive objects in deep \textit{JWST} surveys are severely impacted by cosmic variance.