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Anomalous Narrow-Line Quasars (ANLs) are a population of quasars with narrowH\beta, and sometimes [O III] broader than ~1000 km/s, in total comprising \sim10-30% (most likely ~25%) of Type I quasars at 0.2 < z < 0.8. We find thatvirial masses using the H\beta and Mg II lines systematically differ for ANLsby an average of as much as 0.5 dex. Because the broad H\beta component widthincreases in ANLs but Mg II does not, we might suspect H\beta-based virialmasses for ANLs are wrong but Mg II masses are correct. If this is due to anoutflow reaching the lower-ionization potential H\beta line, C IV masses willbe similarly flawed. However, we cannot be certain of this explanation withoutfollowup work, and may be unable to identify which quasars are ANLs at z > 0.8.Therefore, it is essential that ANLs be well-understood and well-modeled inorder to allow the use of virial mass estimators on large optical spectroscopiccatalogs, particularly at z < 0.4 and z > 2.0 where only one broad line isavailable for use in mass estimation.

Do Anomalous Narrow Line Quasars Cast Doubt on Virial Mass Estimation?