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Effective methods of measuring supermassive black hole masses in activegalactic nuclei (AGN) are of critical importance to studies of galaxyevolution. While there has been much success obtaining masses throughreverberation mapping, the extensive observing time required by this method haslimited the practicality of applying it to large samples at a variety ofredshifts. This limitation highlights the need to estimate these masses usingsingle-epoch spectroscopy of ultraviolet emission lines. We use ultravioletspectra of 44 AGN from HST/COS, IUE, and FUSE of the CIV 1549, OVI 1035, OIII]1664, HeII 1640, CII 1335, and MgII 2800 emission lines and explore theirpotential as tracers of the broad-line region and supermassive black hole mass.The higher S/N and better spectral resolution of the Cosmic OriginsSpectrograph on Hubble Space Telescope resolves AGN intrinsic absorption andproduces more accurate line widths. From these, we test the viability ofmass-scaling relationships based on line widths and luminosities and carry outa principal component analysis based on line luminosities, widths, skewness,and kurtosis. At L_{1450} < 10^{45} erg/s, the UV line luminosities correlatewell with Hbeta, as does the 1450 Angstrom continuum luminosity. We find thatCIV, OVI, and MgII can be used as reasonably accurate estimators of AGN blackhole masses, while HeII and CII are uncorrelated.

Ultraviolet Emission-Line Correlations in Hubble/COS Spectra of Active Galactic Nuclei: Single-Epoch Black Hole Masses