2005ApJ...631L..37R

Several recent studies have determined that large quantities of neutral gas are outflowing from the nuclei of almost all infrared-luminous galaxies. These measurements show that winds in infrared-luminous galaxies play a significant role in the evolution of galaxies and the intergalactic medium at redshifts z≳1, when infrared-luminous galaxies dominated the star formation rate of the universe. These conclusions rely on moderate-resolution spectra (Δv≥65 km/s) of the Na I D absorption line and the assumption that there are no unresolved, saturated velocity components. For the first time, we present high-resolution spectra (Δv=13 km/s) of massive, infrared-luminous galaxies. The five galaxies in our sample are known to host outflows on the basis of previous observations. With the present observations, all Na I D velocity components are resolved with τ(Na I D₁λ5896) ≤ 6. The column densities we measure are consistent within the errors with those measured from moderate-resolution observations. This confirms that the mass, momentum, and energy of outflowing gas in infrared-luminous galaxies have been measured correctly by previous studies.