2015/04/14 by Michael S. Brotherton, M. S. Brotherton, Jessie C. Runnoe +7
Mathematics · Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Statistics Education and Methodologies #astro-ph.GA
paper · pdf · doi:10.48550/arxiv.1504.03427
9 pages, 5 figures, accepted for publication in MNRAS
arxiv created 2015/04/14 · openalex publication_date 2015/04/14 · arxiv updated 2015/04/15 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
The masses of the black holes powering quasars represent a fundamental parameter of active galaxies. Estimates of quasar black hole masses using single-epoch spectra are quite uncertain, and require quantitative improvement. We recently identified a correction for C IV λ1549-based scaling relationships used to estimate quasar black hole masses that relies on the continuum-subtracted peak flux ratio of the ultraviolet emission-line blend Si IV + OIV] (the λ1400 feature) to that of C IV. This parameter correlates with the suite of associated quasar spectral properties collectively known as "Eigenvector 1" (EV1). Here we use a sample of 85 quasars with quasi-simultaneous optical-ultraviolet spectrophotometry to demonstrate how biases in the average EV1 properties can create systematic biases in C IV-based black hole mass scaling relationships. This effect results in nearly an order of magnitude moving from objects with small < peak λ1400/C IV >, which have overestimated black hole masses, to objects with large < peak λ1400/C IV >, which have underestimated values. We show that existing reverberation-mapped samples of quasars with ultraviolet spectra -- used to calibrate C IV-based scaling relationships -- have significant EV1 biases that result in predictions of black hole masses nearly 50% too high for the average quasar. We offer corrections and suggestions to account for this bias.