Galaxies and Their Constituents at the Highest Angular Resolutions fA U Symposium, Vol. 205, 2001 R. T. Schilizzi, S. Vogel, F. Paresce and M. Elvis BIMA Sub-arcsecond Carbon Monoxide Observations: Resolving the Inner kpc Region of the QSO I Zw 1 Johannes Staguhn! Dept. of Astronomy, University of Maryland, College Park, MD 20742, USA Eva Schinnerer Dept. of Astronomy 104-24, California Institute of Technology, Pasadena, CA 91125, USA Andreas Eckart I. Physikalisches Institut , Universitiit zu Koln; Ziilpicher StrafJe 77, 50937 sa«, Germany Abstract. We present the first sub-kpc (rv O. 7" 0.8 kpc) resolution 12CO(I-0) observations of the ISM in the host galaxy of the QSO I Zw 1 which were obtained with the BIMA rum-interferometer in its A config- uration. The measurements, which are part of a multi-wavelength study of I Zw 1, will allow comparison of the ISM properties of a QSO host with those of nearby galaxies and place constraints on galaxy forma- tion/evolution models. Our maps of the 12CO(I-0) line emission from the host galaxy of a QSO show a ring-like structure in the circumnuclear molecular gas distribution with a radius of about 900 pc. The presence of such a molecular gas ring was already predicted from earlier lower angu- lar resolution PdBI observations (Schinnerer, Eckart, & Tacconi 1998). A first comparison of the BIMA data with new PdBI 12CO(2-1) observations with 0.9" angular resolution shows variations in the excitation conditions of the molecular gas in the innermost 3" comprising the nuclear region of I Zw 1. 1. Introduction High resolution molecular line observations of galactic nuclei allow a detailed study of the kinematics of the cold interstellar medium and the derivation of important parameters such as gas masses, surface mass densities and star for- mation efficiencies. Observations with sub-kpc resolution are required for the separation of starburst and AGN components in the nuclei of active galaxies which is a key problem in the investigation of evolutionary sequences proposed for AGNs (Norman & Scoville 1988; Sanders et al. 1988; Rieke, Lebofsky, & 1 Current address: Code 685, NASA - Goddard Space Flight Center, Greenbelt, MD 20771, USA 340 use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900221402 Downloaded from https://www.cambridge.org/core. IP address: 34.228.24.229, on 06 Jun 2020 at 23:51:20, subject to the Cambridge Core terms of