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Ascertain the halo mass and membership of the z=4.90 overdensity hosting RUBIES-EGS-QG-1

Ascertain whether the z=4.90 structure around the quiescent galaxy RUBIES-EGS-QG-1 constitutes an extremely massive dark-matter halo and determine whether the seven additional spectroscopically confirmed sources at similar redshift across the field are physically associated with this overdensity.

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Background

Using JWST spectroscopic redshifts compiled from multiple programs, the authors identify 6 nearby sources within 1 arcmin of RUBIES-EGS-QG-1 and a further 7 sources at similar redshift across the field, indicating a significant overdensity at z=4.90. One of the neighboring sources is a known submillimeter galaxy, suggesting a potentially rich environment.

Despite this evidence for clustering, limitations of the current spectroscopic coverage and selection function prevent a definitive determination of the halo mass scale and membership. The authors explicitly note they cannot conclude whether the structure is an extremely massive halo, nor whether the widely separated sources are members of the same overdensity.

References

However, based on these data alone, we cannot conclusively determine whether the region indeed represents an extremely massive halo, and whether the other 7 sources are associated with the overdensity.

— Efficient formation of a massive quiescent galaxy at redshift 4.9 (2404.05683 - Graaff et al., 8 Apr 2024) in Main text, paragraph discussing the environment and Figure 3 (Spatial clustering map)