Ultraviolet spectra of a large sample of quasars. I. Data and data reduction.

Abstract

Ultraviolet spectrophotometric data on all quasars (Z_e_ > 0.1) obtained with IUE from 1978 to the end of 1986 have been retrieved from IUE archive and re-extracted directly from the photometrically corrected images. A spectrum extraction procedure was used to maximize the signal-to-noise ratio and discriminate against spurious events outside the spectra. This forms a dataset of 117 quasars with 173 spectra in the short wavelength (1250-1950 A) region and 167 spectra in the long wavelength (2200-3200 A) region, respectively. The spectra of known BL Lacs, OVVs (except Q1202 + 281), 3C273 and the double quasar Q0956 + 571 A. B have been excluded from this dataset. This is the ultraviolet sample of quasars. The quasar sample, extraction of the low dispersion spectra and the quality of these data are described. The absolute flux in these spectra is within 7 percent of the absolute flux in the spectra provided by the IUE observatories and this is true for spectra of both high (>10) and low (~3) signal-to-noise ratio, but because of systematic effects in IUE cameras at low signal levels, the absolute accuracy of fluxes in these spectra is about 20 per cent. The median value of the signal-to-noise ratio in the continuum is about six. The quasars in this sample cover an absolute magnitude range from -23 to -30. The analysis of these data will be described in future publications.