Speaker: 　 Prof. Dr. Karl M. Menten (Executive Director, Max-Planck-Institut fuer Radioastronomie)

Affiliation: 　 MPIfR (Max-Planck-Institut fuer Radioastronomie)

Time: 　 2pm, June 4 (Friday)

Location: 　 Middle conf. room, 3rd floor

Abstract: 　
Observations of atomic and molecular absorption can provide important information on the interstellar media of many different types of galaxies. Primary targets are the circumnuclear regions of active galaxies in which the radio continuum from either an AGN or a nuclear starburst (or both) is absorbed. Even lines of modest optical depth in sources with strong continuum emission can be detected. Absorption studies with the next generation of radio astronomy facilities, namely the Expanded Very Large Array and the Five hundred meter Aperture Spherical Telescope have tremendous potential, since their frequency coverage added by a powerful new correlator (EVLA) or a multi-million channel digital spectrometer (FAST) will allow detection of many important lines at virtually any interesting redshift. Both instrument's backends will allow simultaneous measurements of various lines at good spectral resolution. In the special case in which the absorber is the gas-rich lensing galaxy in a gravitational lens system, even single molecular clouds can be studied at high redshift against the "pencil beam" provided by the lensed quasar's compact continuum emission. This has resulted in fascinating astrochemistry studies with often surprising results. Comparison of lines whose frequencies have different dependences on fundamental physical constants provide powerful constraints on potential variability of the proton-to-electron mass ratio, the proton g-factor, and the fine structure constant over large cosmic time scales. We give an overview of the promise of absorption studies possible with the EVLA and FAST which we illustrate with recent examples. In particular, the FAST's huge collecting area will yield a multitude of discoveries.