Keck absorption-line spectroscopy of galactic winds in ultraluminous infrared galaxies

In this paper, we present moderately high resolution (similar to65 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 chi(2) minimization to fit one- to three-component proles 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 out owing, 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)over dot(tot)(H)=13-133 M-circle dot yr(-1) for galaxies hosting a wind. These values of (M)over dot(tot), normalized to the corresponding global star formation rates inferred from infrared luminosities, are in the range eta equivalent to(M)over dot(tot)/SFR = 0.1-0.7. This is on average a factor of only 10 less than eta from recent measurements of nearby dwarfs, edge-on spirals, and lower luminosity infrared galaxies. Within our sample, we conclude that eta 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)> equivalent to Sigma(M)over dot(esc)(i)/Sigma (M)over dot(tot)(i) and "ejection efficiency" <delta> equivalent to Sigma(M)over dot(esc)(i)/Sigma for our sample, which we find to be similar to0.4-0.5 and similar to0.1, 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.