Near-infrared spectroscopy of LINER galaxies

This thesis reports the design and operation of a new near infrared spectrograph for the 5 m Hale telescope and its use to observe a sample of LINER galaxies. The spectrograph operates between 1 and 5 microns using existing infrared array cameras. It has two long-slit spectroscopy modes yielding resolutions ({dollar}lambda{dollar}/{dollar}Deltalambda{dollar}) of {dollar}sim{dollar}850 and {dollar}sim{dollar}3300 with a 0.75" wide by 40" long slit. The spectrograph also has a direct imaging mode giving a 10" x 40" field of view.; The galaxy sample includes 15 LINERs with spectra covering the (FeII) (1.2567 {dollar}mu{dollar}m), Pa{dollar}beta{dollar} (1.2818 {dollar}mu{dollar}m), H{dollar}sb2{dollar} (1-0 S(1), 2.1218 {dollar}mu{dollar}m) and Br{dollar}gamma{dollar} (2.1655 {dollar}mu{dollar}m) near infrared emission lines, and one additional galaxy with only (FeII) and Pa{dollar}beta{dollar} line coverage. The sample included, twelve low luminosity objects (classical LINERs) selected from surveys of nearby galaxies, and four high luminosity multiple nuclei systems.; All of the classical LINERs with infrared line detections have strong (FeII) and/or H{dollar}sb2{dollar} emission, with about half (4 out of 9) having extremely high ratios ({dollar}>{dollar}2) of (FeII) to Pa{dollar}beta{dollar}. The strength of the H{dollar}sb2{dollar} and (FeII) lines is well correlated with the optical (OI) line, with many LINERs having higher ratios of (FeII) /Pa{dollar}beta{dollar}, H{dollar}sb2{dollar}/Br{dollar}gamma{dollar} and (OI) /H{dollar}alpha{dollar} compared to other galaxy types. The LINERs with the highest (FeII) /Pa{dollar}beta{dollar} ratios (termed "strong" (FeII) LINERs) show evidence for recent star formation. Shocks from compact supernova remnants may enhance the (FeII) emission in these "strong" (FeII) LINERs. The LINERs with lower (FeII) /Pa{dollar}beta{dollar} ratios (termed "weak" (FeII) LINERs) are more consistent with Seyfert-like activity, including higher ionization states, some strong x-ray sources and some broad H{dollar}alpha{dollar} detections. The (FeII) luminosity and the (FeII) /Pa{dollar}beta{dollar} ratio in these objects is more easily explained by hard x-ray excitation than in the "strong" (FeII) LINERs. These "weak" (FeII) LINERs are considered prime candidates for being low luminosity Seyfert nuclei.; The two multiple nuclei LINERs with line detections, IRAS 17132 + 5313 and Arp 220, had lower ratios of (FeII) /Pa{dollar}beta{dollar} and/or H{dollar}sb2{dollar}/Br{dollar}gamma{dollar} than the classical LINERs. The spectra of Arp 220 show that the extended emission has higher ratios of (FeII) /Pa{dollar}beta{dollar} and H{dollar}sb2{dollar}/Br{dollar}gamma{dollar} than found on the nuclei. It is suggested that in these merging systems, the low ionization line emission probably results from shocks, either from cloud-cloud collisions or winds in the gas surrounding the nuclei.