Outflows in infrared-luminous starbursts at z < 0.5. I. Sample, Na I D spectra, and profile fitting

We have conducted a spectroscopic survey of 78 starbursting infrared-luminous galaxies at redshifts up to z = 0.5. We use moderate-resolution spectroscopy of the Na I D interstellar absorption feature to directly probe the neutral phase of outflowing gas in these galaxies. Over half of our sample are ultraluminous infrared galaxies that are classified as starbursts; the rest have infrared luminosities in the range log (L-IR/L-circle dot) 10.2-12.0. The sample selection, observations, and data reduction are described here. The absorption-line spectra of each galaxy are presented. We also discuss the theory behind absorption-line fitting in the case of a partially covered, blended absorption doublet observed at moderate-to-high resolution, a topic neglected in the literature. A detailed analysis of these data is presented in a companion paper.