Dynamics of tidal dwarf galaxies in the system Arp 72

Some interactions between galaxies produce tidal tails that are primarily composed of material from their disks. Within these tails, concentrations of gas and stars can form that resemble dwarf galaxies. These tidal objects often begin to form stars and become dynamically independent of their parent galaxies, leading to their classification as tidal dwarf galaxies (TDGs). By definition, TDGs are objects that consist solely of baryonic material, with a negligible dark matter fraction. We analyzed the dynamics of two TDGs in the Arp,72 system using high-resolution Hα observations obtained with the MEGARA multi-spectrograph at the Gran Telescopio Canarias (GTC) and neutral hydrogen i ) data from the Giant Metrewave Radio Telescope (GMRT). The H, i data were also used to determine the gas mass. We derived the rotation curves and velocity dispersion from the kinematic data, which allowed us to estimate the dynamical mass of the systems. The TDGs were modeled through 3D fitting as rotating disks with additional pressure support with a mass distribution following an exponential law. The gas mass was combined with the stellar mass to determine the total baryonic mass. Based on specific dynamical considerations, we established the relation between the dynamical and baryonic mass. Additionally, we used the pressure-support corrected circular velocity to compare the behavior of TDGs in the context of the baryonic Tully-Fisher relation (BTFR) with the literature, showing how detached TDGs fall off the relation. The two objects we studied are consistent with the expected properties of a TDG.