Parsec-scale Magnetic-Field Structures in HEAO-1 BL Lacs

Abstract

We present very long baseline interferometry polarization images of an X-ray selected sample of BL Lacertae objects belonging to the first High Energy Astronomy Observatory (HEAO-1) and the ROSAT-Green Bank (RGB) surveys. These are primarily high-energy-peaked BL Lacs (HBLs) and exhibit core-jet radio morphologies on pc-scales. They show moderately polarized jet components, similar to those of low-energy-peaked BL Lacs (LBLs). The fractional polarization in the unresolved cores of the HBLs is, on average, lower than in the LBLs, while the fractional polarizations in the pc-scale jets of HBLs and LBLs are comparable. However a difference is observed in the orientation of the inferred jet magnetic fields -- while LBL jets are well-known to preferentially exhibit transverse magnetic fields, the HBL jets tend to display longitudinal magnetic fields. Although a `spine-sheath' jet velocity structure, along with larger viewing angles for HBLs could produce the observed magnetic field configuration, differences in other properties of LBLs and HBLs, such as their total radio power, cannot be fully reconciled with the different-angle scenario alone. Instead it appears that LBLs and HBLs differ intrinsically, perhaps in the spin rates of their central black holes.

41 pages, 21 figures, accepted for publication in MNRAS

References in corpus (37)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• A Unifying View of the Spectral Energy Distributions of Blazars
• Structured jets in TeV BL Lac objects and radiogalaxies
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei III. Kinematics of Parsec-Scale Radio Jets
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - I. First-Epoch 15 GHz Linear Polarization Images
• Polarization and structure of relativistic parsec-scale AGN jets
• Spectral energy distributions of a large sample of BL Lacertae objects
• Parsec Scale Properties of Markarian 501
• The Deep X-ray Radio Blazar Survey (DXRBS). I. Methods and First Results
• A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class Division
• TeV candidate BL Lac objects
• Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects: Connection between Superluminal Ejections and Gamma-Ray Flares in Blazars
• A Sample-oriented Catalogue of BL Lacertae Objects
• Helical Magnetic Fields Associated with the Relativistic Jets of Four BL Lac Objects
• The RGB Sample of Intermediate BL Lacs
• A View through Faraday's Fog 2: Parsec Scale Rotation Measures in 40 AGN
• The Parsec-Scale Structure and Jet Motions of the TeV Blazars 1ES 1959+650, PKS 2155-304, and 1ES 2344+514
• Six years of BeppoSAX observations of blazars: a spectral catalog
• The Properties of the X-Ray-Selected EMSS Sample of BL Lac Objects
• Radio Jet-Ambient Medium Interactions on Parsec Scales in the Blazar 1055+018
• Discovery of Very High Energy gamma-rays from 1ES 1011+496 at z=0.212
• Analysis of 6cm VLBI polarization observations of a complete sample of northern BL Lacertae Objects
• Radio-loud active galaxies in the northern ROSAT All-Sky Survey. I. Radio identifications
• Radio-loud Active Galaxies in the Northern ROSAT All-Sky Survey III: New Spectroscopic Identifications from the RGB BL Lac Survey
• A View through Faraday's fog: Parsec scale rotation measures in AGN
• The classification of BL Lacertae objects: the Ca H&K break
• A Sample of Low Redshift BL Lacs. I. The Radio Data
• Parsec-Scale Jet Polarization Properties of a Complete Sample of Active Galactic Nuclei at 43 GHz
• A Viewing Angle - Kinetic Luminosity Unification Scheme For BL Lacertae Objects
• The Radio Structure of High-Energy Peaked BL Lacertae Objects
• VLBI observations of seven BL Lac objects from RGB sample
• The Sub-Luminal Parsec-scale Jet of Mkn 501
• VLBA Polarization Observations of Markarian 421 After a Gamma-Ray High State
• BeppoSAX Observations of Synchrotron X-ray Emission from Radio Quasars
• Measurement of the Integrated Faraday Rotations of BL Lac Objects
• Simultaneous radio-interferometric and high-energy TeV observations of the gamma-ray blazar Mkn 421
• Variations in the broadband spectra of BL Lac objects: millimetre observations of an X-ray-selected sample

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