第121回

On the Tidal Formation of Dark Matter Deficient Galaxies

扇谷 豪 氏

ウォータールー大学

要旨

Recently, observations reported that the ultra diffuse galaxy NGC1052-DF2 (DF2), believed to be a member of the NGC1052 group, is dark matter (DM) deficient. Its inferred DM mass is smaller, by a factor of a few hundred, than what is expected based on its stellar mass and empirical models for galaxy formation and evolution. We consider the tidal interaction between NGC1052 and a smaller satellite galaxy, a possible progenitor of DF2, as the formation scenario of DF2. Our controlled N-body simulations find that DM is preferentially removed from the satellite galaxy and tidal stripping can explain DM deficiency at such levels when assuming a tightly bound and quite radial orbit and cored density structure for the DM halo of the satellite. This tidal formation scenario is updated. Assuming that the satellite galaxy was accreted early enough, the observationally inferred upper mass limit of DF2 is reproduced for cuspy density structures of the DM halo surrounding the satellite galaxy. We also study the orbital evolution of globular clusters in the satellite galaxy and find that the injection of kinetic energy in the tidal interaction suppresses the orbit decay of the globular clusters due to dynamical friction. This mechanism can be a key to explain the expanded distribution of globular clusters in DF2.