A Relation between Supermassive Black Hole Mass and Quasar Metallicity?

We analyze spectra for a large sample of 578 Active Galactic Nuclei toexamine the relationships between broad emission line properties and centralsupermassive black hole (SMBH) mass. We estimate SMBH masses by applying thevirial theorem to the C IV lambda 1549 broad emission line. Although the FWHMsof C IV and H beta appear nearly unrelated in individual objects, these FWHMsare well correlated when averaged over sub-samples in our database. Therefore,the lines are equally valid indicators of the average SMBH mass in quasarsamples. Our sample spans five orders of magnitude in SMBH mass, six orders ofmagnitude in luminosity, and a redshift range from 0 <= z <= 5. Most linesdiminish in equivalent width with increasing black hole mass (the usual"Baldwin Effect") and there are no trends with redshift. Recent studiesindicate that there is a relationship between SMBH mass and the overallbulge/spheroidal component mass of the surrounding galaxy. This relation,together with the well-known mass-metallicity relationship among galaxies,predicts a relationship between SMBH mass and quasar metallicity. We estimatethe metallicity in the broad emission line region by comparing several lineratios involving nitrogen to theoretical predictions. We find that the data areconsistent with a trend between SMBH mass and metallicity, with some lineratios indicating a very strong trend, but the uncertainties in several otherimportant line ratios are too large to confirm or test this correlation.Comment: 21 pages, including 11 figures and 2 table