Elvis, MartinWilkes, BelindaLockman, Felix J.2017-02-131989Elvis, Martin, Belinda J. Wilkes, and Felix J. Lockman. 1989. “Accurate Galactic N(H) Values Towards Quasars and AGN.” The Astronomical Journal 97 (March): 777. doi:10.1086/115022.0004-6256http://nrs.harvard.edu/urn-3:HUL.InstRepos:30212152Integrated Galactic 21-cm column densities toward about 174 quasars and AGN are presented. The data are corrected for stray radiation, using the technique of Lockman et al. (1986). Because of the 21-arcmin beam size of the 140-ft telescope used in the study, the uncertainty in N(H) due to angular variations in the H I of the Galaxy at high latitudes is minimized. The column densities are accurate to about 1 X 10 to the 19th atoms/sq cm, or 5 percent, whichever is larger. Errors above N(H) of about 4 X 10 to the 20th atoms/sq cm are dominated by opacity uncertainties.en-USActive Galactic NucleiQuasarsSky Surveys (Astronomy)X Ray SourcesBrightness TemperatureH LinesHeao 2Radiation SpectraSignal To Noise RatiosJournal Article2017-02-1310.1086/115022