BL LAC OBJECTS

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BL LAC OBJECTS

• Marco Bondi
• INAF-IRA, Bologna, Italy

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A beamed review

• This review includes
• Recent (2-3 years) developments on a few selected
  topics.
• This review will NOT cover
• Polarization properties
• Parent population of BL Lacs and unified schemes

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Outline

• The Blazar family
• New samples of BL Lacs
• Pc-scale kinematics
• Broad-band correlations
• Future developments

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The Blazar Familye.g. Urry Padovani '95

• SED dominated by sync and IC processes from radio
  to gamma-ray.
• Flat radio spectra, extreme variability, high
  polarization (radio optical), different opt
  spectroscopic properties.
• Unified scheme BL Lacs as low luminosity
  blazars.

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New samples of BL Lacs why we need them ?

• The starting point the blazar sequence
  (Fossati
  et al.1998)
• HBL,
  LBL, FSRQ

• lack of
• low power low-energy peaked obj
• high power high-energy peaked obj

Warning !!! Based on 3 highly biased samples
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New samples of BL Lacs testing the blazar
sequence with CLASS

• The CLASS Blazar Sample (Caccianiga Marcha
  '04) 300 flat spectrum, gt 30 mJy, sources.
• Motivation looking for weak X-ray emitter BL
  Lac, i.e. steep radio-to-X-ray spectral index.
• Results a significant and large fraction of low
  luminosity blazars in the sample lie outside the
  blazar sequence
• See also H. Bignall's talk.

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New samples of BL LacsHST and VLBI obs of
nearby objectssee M. Giroletti poster

• Nearby (zlt0.2) BL Lacs from the HST snapshot
  image survey (Giroletti et al. '06).
• Core dominance, jet/counter-jet ratio, SSC models
  used to constrain beaming parameters ? 4
  
  
  
  
  
  
  

Common origin for radio and optical core
emission
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AGN Jets the fundamental questions modified
from Lister '03

• AGN jet speed distribution
• fast or slow jets ? what is the maximum jet speed
  ?
• Velocity profile
• radial decelerating jets ?
• transverse spine layer ?
• Relation of jet speed to other AGN properties
• dependence on BH mass ? optical class ?
• are more luminous jets faster ?
• which AGN have fastest jets ?

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Jet speed distribution

• Jorstad et al. 2005 7mm, 17 epochs,
• Some of the most extreme values confirmed (e.g.
  Piner et al. '06)

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Pc-scale kinematics TeV sources

• Jet motions in TeV BL Lacs (Piner Edwards '04)
  multi-epoch 15 Ghz observations

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TeV BL Lacs pc-scale kinematics

• Jet motions in TeV BL Lacs (Piner Edwards '04)
  multi-epoch 15 Ghz observations
• Similar jet morphologies collimated, bending,
  transition to diffuse emission (see also Rector,
  Gabuzda Stocke '03)
• Components in TeV BL Lacs are predominatly
  stationary or subluminal ? 2-4 (also Giroletti
  etal '04)

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TeV BL Lacs radio and gamma ray beaming factors

• ?(VLBI)2-4 ?(SED,gamma-ray)10-50
• Jet velocity structure
• Radial strong deceleration (Georganopoulos
  Kazanas '03)
• Transverse fast spine and slow layer (Ghisellini
  et al '05)
• one component sees the beamed radiation produced
• from the other and this yields to enhanced
  gamma-ray emission.

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TeV BL Lacs radio and gamma ray beaming factors

• Conical jet model (Gopal-Krishna et al. '06)
• each element of the jet cross section is boosted
  by a different amount because having different
  misaglinement. The inferred ? are
  underestimated.

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Coordinated broad-band campaignsradio-optical

• Whole Earth Blazar Telescope (WEBT) campaigns
  provided an unprecedented time sampling for radio
  and optical light curves
• BL Lac (Bach et al. '06)
• 3C 66A (Bottcher et al. '05)
• 0235164 (Raitieri et al. '05)
• Major optical bursts linked to flux density and
  polarisation variations in the VLBI core with no
  apparent changes in the VLBI jet. Confirmed in
  OQ530 (Massaro et al. '04)

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WEBT Campaigns on BL LAC itselfBach et al. '06

• 10 years optical and VLBI monitoring.
• VLBI allows to disentangle the different
  components contributing to the single dish radio
  light curves.
• Results
• spectral variability in the single-dish data
  traces the variability of the VLBI core.
• fair correlation (time delay between 50-150 days)
  between variations in the optical and radio band.
  

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Coordinated broad-band campaignsradio-gamma-ray

• Connection between gamma-ray outbursts and the
  ejection of VLBI components have been found (Pohl
  et al. '95, Jorstad et al. '01, Lähtenmäki
  Valtaoja '03).
• Correlated radio and TeV variability in Mkn 421
  investigated by Charlot et al. 06
• variations on few weeks timescale in the VLBI
  core
• no significant variations in the VLBI jet

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Future AGILEhttp//agile.rm.iasf.cnr.it

• Gamma-ray (30 MeV-30 GeV) and hard X-ray (15-45
  keV) imaging
• Consortium of Italian partners
• Launch 2007

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AGILE gamma ray detector

• Source location determination
• 5-20 arcmin (about twice better than EGRET)
• Sensitivity
• comparable to EGRET on-axis, better for off-axis
• FOV
• 3 sr, about 6 times EGRET's
• sensitivity for a 1-year all sky survey 3 times
  better than EGRET
• Broad-band monitoring of AGNs