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Observations and Data Reduction

The optical redshifts were obtained using the Double Spectrograph (Oke & Gunn 1982) on the 5 m Hale Telescope at Palomar Observatory on two separate occasions. The majority of the data were collected on the nights of 1987 June 23-28 by P. B. H., J. R. H., and B. T. S. More spectra were collected over the period 1990 June 23-28 by M. L. N. A., P. B. H., and J. R. H. In both cases the Double Spectrograph was configured with a dichroic/beamsplitter to provide spectral coverage over the region 3800 Å to 10,000 Å. The 158 lines mm^-1 and 300 lines mm^-1 gratings were used in the red and blue cameras, respectively, yielding resolution of roughly 6 Å per pixel at H and 3 Å per pixel at H . All observations were made through a 1" slit. Exposure lengths varied from 300 s to 1200 s. Atmospheric seeing during the observations was generally between 1" and 2" FWHM. The sample is tabulated and the observations are summarized in Table 1.

We followed routine IRAF reduction procedures to extract the redshift data from our spectra. Bad pixels and cosmic-ray hits were removed from the spectra by replacement with averages of the nearest neighbor pixel values. Standard star and source spectra were flat-fielded with spectra of the telescope dome illuminated by incandescent lights. Background illumination was removed from red and blue spectra by subtracting a linear fit to the emission on either side of the nuclear continuum emission The wavelength scale was calibrated using discharge lamp spectra taken after each exposure on an IRAS NEPR source. Sensitivity calibration was performed using short (2-5 s) exposures on the standard stars BD + 17"4708 and BD +26° 2606 (Oke & Gunn 1983). The spectra were then compressed to one-dimensional format.

Some NEPR galaxies were found to have more than one optical component within the 45" positional errors presented by Hacking & Houck (1987). These are marked in Table 2 with the notation N. S. E, or W to indicate the offset direction from the IRAS source positions. We aligned the Double Spectrograph slit to include multiple sources when possible and thus acquire redshifts for two sources in a single exposure. In most eases such multiple sources were found to be at similar if not identical redshifts (17514+6534 NW and SE are exceptions). Thus, out of 80 exposures taken, we extracted a total of 88 spectra. In all, spectra were obtained for 77 of the 99 NEPR sample sources. One of these (F18066+6632) was analyzed in Ashby, Houck, & Hacking (1992).

Emission line positions were extracted and identified from red and blue spectra for each galaxy observed. We present redshifts only for those sources for which we could make more than one line identification (in several cases, especially for the companion galaxies but also for five isolated objects, it was not possible to make corroborating line identifications). These ``weak" sources are marked with ellipses in Table 2 and will not be considered further in this paper. We note for the sake of completeness only the borderline case 18096 + 6734 (3-89), which has weak (3 ) features consistent with [O II] 3727 emission and Ho absorption at a redshift of z = 0.029, but because it lacks Ha or any other emission features longward of 5500 A we choose to treat its redshift as undetermined. In addition, 17479 + 6735 (3-02) has a strong continuum with zero redshift Balmer decrement absorption lines and no detectable emission lines. We conclude from this and the fact that the 25-60 m color for 17479 + 6735 is indicative of a galaxy that we have observed the wrong object. Finally, 3-52 is NGC 6543, a bright planetary nebula. Thus, we are left with a sample of 76 sources for which redshifts have been determined.

Redshift data for the 76 NEPR sources are presented in Table 2. The redshift error is typically . A histogram of the redshift distribution is presented in Figure 2 below. The median sample redshift is z = 0.080.

  Observing Log

Galaxy Hacking Position Date Time Galaxy Hacking Position Date Time

(1987) (1950) Observed (s) (1987) (1950) Observed (s)

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