14 January, 2006 - 11:25 AM
CO(1-0) emission from QSO host galaxies beyond redshift 4
Dominik A. Riechers (MPIA Heidelberg), Fabian Walter (MPIA Heidelberg), Christopher L. Carilli (NRAO Socorro), Kirsten K. Knudsen (MPIA Heidelberg), K. Y. Lo (NRAO Charlottesville), Dominic J. Benford (NASA/GSFC), Johannes G. Staguhn (NASA/GSFC), Todd R.
Molecular gas has now been detected in 15 z > 2 QSOs through observations of high-J CO transitions using millimeter interferometers. Observations of the CO ground-state transition, CO(1-0), however, have the potential to trace the molecular gas at lower excitations which may give a better estimate of the total molecular gas content in high-z QSOs. Here we present first z > 4 CO(1-0) observations obtained with the NRAO Green Bank Telescope (GBT) and the MPIfR Effelsberg telescope. Utilizing the K band receivers of these two 100m class radio telescopes, we detect the CO(1-0) transition in the high-redshift QSOs BR 1202-0725 (z = 4.7), PSS J2322+1944 (z = 4.1), and APM 08279+5255 (z = 3.9). The spectral capabilities of the GBT (1 × 200 MHz in high-resolution mode, 2 × 800 MHz in high-bandwidth mode) allow us to cover velocity ranges of up to 20000 km s-1, or Δ z/z = 0.09 at z = 4, which will be imperative for future high-z studies in galaxies with known strong dust continuum, but poorly constrained redshift. This is a first step towards observations with future z-machines. From our observations out to z = 4.7, we find that the CO/FIR luminosity ratios of our high-z sources follow the same trend as seen for low-z galaxies. We also derive that CO emission from all observed transitions can be described by a single gas component and that all molecular gas appears to be concentrated in a compact nuclear region.