A Physical Classification Scheme for Blazars

Abstract

Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars (FSRQ) based on the strength of their emission lines. This is done rather arbitrarily by defining a diagonal line in the Ca H&K break value -- equivalent width plane, following Marcha et al. We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS) and 2 Jy radio survey and find a significant bimodality for the narrow emission line [OIII] 5007. This suggests the presence of two physically distinct classes of radio-loud AGN. We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII] 5007 -- [OII] 3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.

19 pages, 10 figures. Accepted for publication in MNRAS

References in corpus (12)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• Jets and accretion processes in Active Galactic Nuclei: further clues
• The Deep X-ray Radio Blazar Survey (DXRBS). I. Methods and First Results
• A test for partial correlation with censored astronomical data
• The RGB Sample of Intermediate BL Lacs
• The Deep X-ray Radio Blazar Survey (DXRBS). II. New Identifications
• The classification of BL Lacertae objects: the Ca H&K break
• Understanding the nature of FRII optical nuclei: a new diagnostic plane for radio galaxies
• Origin of the viewing-angle dependence of the optical continuum emission in quasars
• The REX survey: a search for Radio Emitting X-ray sources
• The CLASS blazar survey. I - selection criteria and radio properties
• Host Galaxies of low z Radio-loud Quasars: A search of HST archives

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