ИСТИНА

The low surface brightness disc galaxy Malin2 challenges the standard theory of galaxy evolution by its enormous total mass ~2 10^12 Ms which must have been formed without recent major merger events. We performed the Malin2 mass modelling, estimated the contribution of the host dark halo and found that it had acquired its low central density and the huge isothermal sphere core radius before the disc subsystem was formed. One of the unique properties of Malin2 turned to be the apparent imbalance of ISM: the molecular gas is in excess with respect to the atomic gas for given values of the gas equilibrium turbulent pressure. We explain this imbalance by the presence of a significant portion of the dark gas not observable in CO and the 21 cm lines. We also show that the depletion time of the observed molecular gas traced by CO is nearly the same as in normal galaxies.