2022ApJ...934L..35C

Low-mass compact stellar systems (CSSs; M_⋆ < 10¹⁰M_⊙) are thought to be a mixed bag of objects with various formation mechanisms. Previous surveys of CSSs were biased to relatively high-density environments and cannot provide a complete view of the environmental dependence of the formation of CSSs. We conduct the first-ever unbiased flux-limited census of nearby quiescent CSSs over a total sky area of ∼200 deg² observed by the GAMA spectroscopic survey. The complete sample includes 82 quiescent CSSs, of which 85% fall within the stellar mass range of classical compact ellipticals (cEs). By quantifying the local environment with the normalized projected distance D/R_vir to the nearest luminous neighboring galaxy, we find that these CSSs have a bimodal D/R_vir distribution, with one group peaking near ∼0.1 × R_vir (satellite) and the other peaking near ∼10 × R_vir (field). In contrast to the CSSs, ordinary quiescent galaxies of similar masses have a unimodal D/R_vir distribution. Satellite CSSs are older and more metal-rich than field CSSs on average. The bimodal D/R_vir distribution of quiescent CSSs reinforces the existence of two distinct formation channels (tidal stripping and born-to-be) for cEs and may be understood in two mutually inclusive perspectives, i.e., substantial tidal stripping happens only when satellite galaxies travel sufficiently close to their massive hosts, and there exists an excess of high-density cE-bearing subhalos close to massive halos.