Galactic H I column densities toward quasars and active galactic nuclei

We have determined accurate values of the Galactic neutral hydrogen column density, N-H, toward 220 quasars and active galactic nuclei from 21 cm H I measurements made on the 140 Foot Telescope (42.7 m). Accurate values of N-H have now been obtained for the whole PG bright quasar sample and most quasars that have been observed by ROSAT and the Hobble Space Telescope through mid-1993. The spectra were corrected for stray 21 cm radiation yielding values of N-H with a typical uncertainty of 1 x 10(19) cm(-2) for high Galactic latitude directions. The H I column densities will be useful for correcting for interstellar opacity at UV and soft X-ray wavelengths, and for estimating the reddening and extinction toward these objects.