Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies
Andrew Harris
Department of Astronomy, University of Maryland
The molecular ISM of high-redshift galaxies
Recent developments have expanded the number of molecular lines available to explore the molecular interstellar medium in galaxies at high redshifts. The additional information provides new constraints on the physical state of the molecular gas, a tracer of the material associated with star formation.\\
Here we present Zpectrometer/GBT observations of the rest-frame 3~mm waveband from a number of galaxies in the redshift range $z = 2$ to 3. The Zpectrometer is an ultra-wideband spectrometer built specifically to search for and characterize low-excitation transitions in high-redshift galaxies. Observations of low-excitation lines provide surprisingly strong constraints on the warm ISM as well as the cool components.\\
As part of discussing the multi-phase ISM revealed by the Zpectrometer, we also present associated new molecular line results from the GBT, PdBI, 30~m, and SMA telescopes on the brightest submillimeter galaxy known, the ``Cosmic Eyelash.''\\
Our approach includes a critical treatment of the constraints modeling can provide given a range of lines at different energies and systematic errors. While some high-redshift galaxies seem to have interstellar media that can be characterized by single-component models, something that is not observed in local galaxies, new data are beginning to reveal more complex conditions within high-redshift nuclei. The results are a foretaste of the results that ALMA, the EVLA, and the GBT will harvest in coming years.\\
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