3C120 R. Craig Walker National Radio Astronomy Observatory Socorro, NM Collaborators: J.M. Benson,...
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Transcript of 3C120 R. Craig Walker National Radio Astronomy Observatory Socorro, NM Collaborators: J.M. Benson,...
3C120
R. Craig WalkerNational Radio Astronomy Observatory
Socorro, NM
Collaborators: J.M. Benson, S.C. Unwin, M.B. Lystrup, T.R.Hunter, G. Pilbratt, P.E. Hardee, D. HarrisVLBA 10th Anniversary June 9, 2003
Why 3C120?• Quasar-like properties but “nearby”
– z=0.033 D~125 Mpc Scale: 0.6 pc/mas– One of closest superluminals
• High angular rates (2.5 mas/yr)
• Prime monitoring candidate
– Large (~1') optical galaxy with emission lines• Underlying structure unclear – “train wreck”
• Jet detected in optical and x-ray
• Long history of observations
HST images obtained from archive by D. Harris and T. Cheung
3C120 VLBA 1.7 GHz Monitoring Project
Observations so far: 1994.44, 1997.70, 2000.68, 2002.76Also earlier MarkII observations at 1982.77, 1984.26, and 1989.85
50 pc(80 mas)
• Superluminal and slow moving components• Possible helical pattern at 50 pc (80 mas)
Helical Pattern• Pattern near 50 pc (80 mas) looks like helix in
projection and is moving slowly – Superluminal features move through it
• Simple “beads on a string” model requires extremely small angle to line-of-sight
• Reasonable geometry if high pressure (high brightness) region is toward outside of jet
– Pattern follows wider opening angle helix than individual particles
– Expected from instability theory
Preliminary Polarization ImageNote 90° rotation
HELICAL INSTABILITIES• Work by Phil Hardee (See poster 17)• The VLBI data constrains:
– Component speeds– Pattern speeds– Brightness distribution
• Model with helical instabilities. Try to determine:– Viewing angle and flow speed– Internal and external sound speeds– Perturbation frequencies
• Goal to learn about jet content and physics.
Psuedo-synchrotron images for low, medium, and high frequency models for hot and warm jets.
Multiple perturbation frequency models from side and from near 14° viewing angle
3C120 VLBA High Resolution• Observations by Gómez, Marscher, Agudo, Alberdi and others• Monthly observations at 22 and 43 GHz with full polarization• Have shown evidence for:
– Flashing components: External interactions (Gómez et al., Science 289, 2317)
– Trailing components: Shock physics (Gómez et al., Ap. J. 561, L161, Agudo et al., Ap. J. 549, L183
– Xray correlation: X-ray dip at component ejection (Marscher et al Nature 417, 625)
• Also monitored at 15 GHz by Homan, et al. (Ap. J. 549, 840)
Note Gómez talk this meeting
22 GHz
3C120 from 1" to 30" (VLA 5GHz)
Jet very one-sided
4 knot is subluminal
Note possible helical pattern
25 knot
Core
Dynamic range (peak/rms) ~250,000
Walker Ap. J. 488, 675
HST –VLBI/MERLIN – VLA Overlay• Radio knot at 4 has
optical (and x-ray) counterparts on what looks like a spiral arm.
• Superluminal motion in inner radio jet implies that the jet is close to the line-of-sight.
• Is the “spiral arm” along the line-of-sight? The rest of the galaxy looks face on. Is it a tidal tail?
• Low spatial resolution optical spectra are double peaked near the knot – and on the opposite side (Axon et al., Nature, 341, 631)
-400
400
V
0 20• Hjorth et al see optical jet beyond 4 knot (ApJ 452, L17)
Chandra X-ray Detections
• X-rays seen at core, 4 and 25 knots, jet near 8
• Diffuse x-rays and weak radio near 25 knot (right)
• Probably synchrotron emission at 4 knot
• Emission mechanism at 25 knot is a puzzle, especially in the diffuse region to northeast
Chandra data is a zero order grating image from Tahir Yaqoob
SUMMARY• 3C120 is a rich source of data
on the jet phenomenon • VLBA monitoring provides
dynamics for comparison with theory– High frequency observations of
inner few pc– 1.7 GHz observations of helical
pattern at 50 pc
• Optical: possible interaction with spiral arm or tidal tail at 4" knot
• X-ray: emission mechanism puzzle at 25" knot