Gas kinematics in the halo of the warm ULIRG PKS1345+12

Abstract

We use long-slit spectra taken with the William Herschel Telescope on La Palma and high-resolution Hubble Space Telescope imaging to study the gas kinematic in the halo of the ultraluminous infrared/radio galaxy PKS1345+12 ( z=0.122). Our long-slit spectra show line splitting at the locations of massive star clusters ( 10⁶<M_{SSC}^{YSP}<10⁷ M_⊙), indicating that they are moving at up to 450 km s^-1 with respect to the local ambient gas. Given their kinematics, it is plausible that these super star clusters have been formed either in fast-moving gas streams or tidal tails that are falling back into the nuclear regions as part of the merger process, or as a consequence of jet-induced star formation linked to the extended, diffuse radio emission detected in the halo of the galaxy.