Determine the eventual descendant of the Building Blocks System

Determine whether the Building Blocks System will evolve into a present-day massive galaxy such as the Milky Way or instead represent the main, most massive branch of the merger tree leading to such a galaxy.

Background

The Building Blocks System is a compact group of three low-mass galaxies observed at redshift 5.2, approximately 1 Gyr after the Big Bang, whose close projected and velocity-space proximity suggests that the members are interacting and likely to merge. Abundance-matching calculations indicate that the system’s present stellar mass is consistent with the expected progenitor mass of a present-day Milky Way- or M31-mass galaxy.

However, abundance matching provides a population-level evolutionary expectation rather than a deterministic trajectory for this particular object. The paper therefore leaves unresolved whether the observed system itself will become such a massive galaxy, or whether it is only the dominant branch within a larger merger tree whose eventual descendant is a massive galaxy.