2002ApJ...570..588R

In this paper, we present moderately high resolution (∼65 km.s^–1) spectroscopy, acquired with the Echellette Spectrograph and Imager on Keck II, of 11 ultraluminous infrared galaxies at z<0.3 from the IRAS 1 Jy sample. The targets were chosen as good candidates to host galaxy-scale outflows, and most have infrared luminosities dominated by star formation. We use a χ² minimization to fit one- to three-component profiles to the Na I D interstellar absorption doublet in each object. Assuming that gas blueshifted by more than 70 km.s^–1 relative to the systemic velocity of the host is outflowing, we detect outflows in 73% of these objects. We adopt a simple model of a mass-conserving free wind to infer mass outflow rates in the range M{dot}_tot(H)=13-133 M_☉ yr^–1 for galaxies hosting a wind. These values of M{dot}_tot, normalized to the corresponding global star formation rates inferred from infrared luminosities, are in the range η≡M{dot}_tot/SFR=0.1-0.7. This is on average a factor of only 10 less than η from recent measurements of nearby dwarfs, edge-on spirals, and lower luminosity infrared galaxies. Within our sample, we conclude that η has no dependence on the mass of the host (parameterized by host galaxy kinematics and absolute R- and K'-band magnitudes). We also attempt to estimate the average escape fraction <f_esc>≡∑M{dot}ⁱ_esc/∑M{dot}ⁱ_tot and ``ejection efficiency'' <δ>≡∑M{dot}ⁱ_esc/∑SFRⁱ for our sample, which we find to be ∼0.4-0.5 and ∼0.1, respectively. The complex absorption-line properties of Mrk 231, an ultraluminous infrared galaxy that is optically classified as a Seyfert 1, are discussed separately in an appendix.