Galaxy lacking dark matter in the standard cosmological paradigm

Abstract

The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark matter halos and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several simulations using the conventional cosmology failed to adequately form numerical analogs. Here we show that the standard paradigm naturally produces galaxies lacking dark matter, with characteristics largely in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close-encounters with massive neighbors can transform regular galaxies into dark-matter deficient ones. We predict that ∼30% of massive central galaxies (with at least 1e11 solar masses in stars) harbor at least one dark-matter deficient satellite (with 1e8−1e9 solar masses in stars). This distinctive class of galaxies opens an additional layer to our understanding of the role of interactions in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.