Determine the genuine isolation of galaxies near the survey magnitude limit

Determine whether galaxies in the MASSES3-ISO sample with an accessible magnitude range below four magnitudes above the survey limit are genuinely isolated, rather than appearing isolated because companions below the survey magnitude limit remain undetected.

Background

The MASSES3-ISO sample is defined using GAMA galaxies classified as non-grouped by the friends-of-friends catalogue. However, the survey’s finite magnitude limit means that galaxies near this limit may possess undetected companions. The authors quantify isolation through the accessible magnitude range, Δr, between a galaxy’s effective dust-corrected apparent magnitude and the survey limit.

Galaxies with Δr below four magnitudes could have companions with luminosity ratios as high as approximately 1/40 that are missed by the survey. Consequently, their apparent isolation cannot be established in the stronger sense used for the ISO4 and ISO5 subsamples, which are at least four or five magnitudes brighter than the survey limit.

References

It is therefore uncertain whether these are genuinely isolated or not (except in the sense that they do not have nearby galaxies brighter than or similar to themselves).

— Galaxy And Mass Assembly (GAMA): The Most Isolated GAMA Galaxies  (2609.29753 - Phillipps et al., 24 Sep 2026) in Section 2, Data and Samples, paragraph immediately preceding the subsection “High luminosity ratio grouped galaxies”