IC 4200: a gas-rich early-type galaxy formed via a major merger
  We present the result of radio and optical observations of the S0 galaxy IC 4200. We find that the galaxy hosts 8.5 billion solar masses of HI rotating on a ~90 deg warped disk extended out to 60 kpc from the centre of the galaxy. Optical spectroscopy reveals a simple-stellar-population-equivalent age of 1.5 Gyr in the centre of the galaxy and V- and R-band images show stellar shells. Ionised gas is observed within the stellar body and is kinematically decoupled from the stars and characterised by LINER-like line ratios.We interpret these observational results as evidence for a major merger origin of IC 4200, and date the merger back to 1-3 Gyr ago. 
P. Serra (1), S. C. Trager (1), J. M. van der Hulst (1), T. A.   Oosterloo (1,2), R. Morganti (1,2) ((1) Kapteyn Astronomica...