Speaker
Description
In the standard cosmology, dark matter drives the structure formation of galaxies and constructs potential wells within which galaxies may form. The baryon fraction in dark halos can reach the Universal value (15.7%) in massive clusters and decreases rapidly as the mass of the system decreases. The formation of dwarf galaxies is sensitive both to baryonic processes and the properties of dark matter, owing to the shallow potential wells in which they form. In dwarf galaxies, in the Local Group, dark matter dominates the mass content even within their optical-light half-radii (re ≈ 1 kpc). However, recently it has been argued that not all dwarf galaxies are dominated by dark matter. We found 19 Dark-Matter-deficient Dwarf Galaxies (DMDGs) that could consist mainly of baryons up to radii well beyond re, at which point they are expected to be dominated by dark matter. An explanation of such dwarf galaxies from hydrodynamical simulations shows that interactions of galaxies at high-density regions could be responsible for the formation of baryon-dominated tidal dwarf galaxies, and environmental stripping could play a role in forming the DMDGs around galaxy clusters. Indeed, it is more challenging to explain the existence of DMDGs (14/19) in the fields where their formation and evolution are free from the environment. Such kind of system challenges the current galaxy formation theory and could also provide new clues for the nature of dark matter (e.g., warm dark matter, fuzzy dark matter, SIDM, or MOND). Based on VLA observations, we have dynamically confirmed, for the first time, an isolated dark-matter–deficient dwarf galaxy. Further observations are required to establish a statistically significant sample and to unveil the formation mechanisms of these intriguing dwarf galaxies.
