Molecular Gas and Star Formation in the Host Galaxy of the QSO I Zw 1
  We have investigated the ISM of the I Zw 1 QSO host galaxy with Plateau de Bure mm-interferometry and high angular resolution near-infrared imaging spectroscopy. We have detected a circumnuclear gas ring of diameter ~ 1.5'' (1.8 kpc) in its millimetric CO line emission and have mapped the disk and the spiral arms of the host galaxy in the ^{12}CO(1-0) line at 115 GHz as well as in the H (1.65 um) and K (2.2 um) band . Combining our new mm- and NIR-data with available estimates of the radio- and far-infrared contributions to the nuclear emission, we find strong evidence for a nuclear starburst ring. A comparison to other sources with nuclear activity indicates that these rings may be a common phenomenon and contribute a large fraction of the central luminosity. 
E. Schinnerer, A. Eckart, L.J. Tacconi (all MPE, Garching)