Radio-Loud and Radio--Quiet Quasars from the SDSS Database

摘要

Using a sample of ～ti 3000 radio loud quasars (RLQs) included in the Sloan Digital Sky Survey, with 0.35 ≤ z≤2.25, we study the dependence on the redshift of the black hole (BH) mass, through the application of an analysis scheme which overcomes the problems related to the Malmquist bias. Comparing the results with those from a sample dominated by radio quiet quasars (RQQs), we find that RLQs are on average inure massive than RQQs and suggest that the difference fades out at z≈ 3. We relate the BH mass gap to the observed different colors of the continuum in RLQs and RQQs and propose a picture of interpretation in terms of distinct accretion disc temperatures in the two pop-ulation of quasars. Another possible explanation of the observed differentiation hi the BH mass z-dependence of RLQs and RQQs is that it is due to the effects of radiation pressure: RLQs are proposed to have a lower column density in the broad line region with respect to RQQs.