DELVE 8/Gemini I: A Spectroscopic Window into Ambiguous Halo Substructure Beyond Simple Dwarf Labels

The arXiv preprint (not yet peer-reviewed) reports discovery of DELVE 8/Gemini I via cross-matching two search algorithms on DELVE DR3 DECam imaging, followed by Gemini/GMOS-N confirmation and Keck/DEIMOS medium-resolution spectra securing four members at 120 kpc. This places the system among the rare ultra-faint compact objects where half-light radius (8.6 pc) and luminosity (MV=-2.1) alone cannot distinguish star cluster from dwarf galaxy. The work correctly flags the metallicity upper limit [Fe/H] ≲ -2.5 from the brightest star but underplays how such distant systems test predictions of dark-matter subhalo mass functions at large radii, a regime where simulations like those in Nadler et al. (2020, ApJ) show tension with observed satellite counts. Earlier DELVE papers (e.g., Mau et al. 2020) focused on closer systems; this object extends the search volume and reveals that velocity dispersion measurements will require larger spectroscopic samples than the current n=4 to break the degeneracy. Mainstream coverage often misses that these ambiguous satellites may trace the low-mass end of the subhalo spectrum rather than representing a new dwarf population, directly informing models of reionization and tidal stripping at 100+ kpc.