Determine the nature of GHZ2 at redshift 12.33

Determine whether the galaxy GHZ2 at redshift z = 12.33 is a star-forming galaxy or an active galactic nucleus, thereby establishing whether it is appropriately described by the compact high-redshift star-forming galaxy model.

Background

GHZ2 is included in the high-redshift galaxy sample used to study the transition from supernova-produced dust to dust growth in the interstellar medium. Its classification is relevant because the model applied in the paper describes compact star-forming galaxies and may not be valid if the source is dominated by an active galactic nucleus.

The paper reports that competing interpretations have been proposed for GHZ2. The authors therefore include the object in their fiducial censored analysis but repeat the change-point and bootstrap calculations without it to assess whether the inferred dust transition depends on the unresolved classification.