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Winged and X-shaped radio
galaxies
Gijs Verdoes Kleijn
OmegaCEN / Kapteyn Astronomical Institute
University of Groningen, NL
Teddy Cheung (NASA/Goddard, USA),
Hermine Landt (Univ. Melbourne, Australia),
Andres Jordan (Univ. Catolica, Chile),
Stephen Healy (Stanford, USA)
Outline
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Intro “winged” and X-shaped radio galaxies
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Observations and models/scenarios
Are they important for understanding (radio) galaxy
evolution?
Sample
Preliminary results
Winged and X-shaped radio galaxies
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Winged population ~7-10% of
3CR radio galaxy population
(Leahy & Williams 1984)
Radio morphology
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Primary radio lobes
Secondary pair of lobes/wings
Canonically: size
secondary/primary>0.8
Additional lobes show no signs
of active jet or hotspot
A subset has well defined Xshape
3C403 (Kraft et al. 2005)
Winged radio galaxies, examples
NGC326;
Ekers+78, Murgia+01
3C223.1; Dennett-Thorpe+02
Mixed bag?
From Reynolds+09
Formation models
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1.
Two classes of model
Jet orientation fixed:
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2.
Jets energize active lobes
Wings created by “blowout”
of the backflow
(overpressure / buoyancy)
Jet re-orientation:
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Rapid realignment of jets
leaving fossil lobes in old
direction and new active
lobes (trealign<106yr)
Change of spin axis
BH/accretion disk SMBH
merger
Scheuer (1974)
See also Dennett-Thorpe et al.
(2002), Merritt & Ekers (2002);
Komossa (2003)
Hydrodynamical model favored?
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Pro:
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Wings roughly align with optical (Capetti+02)
and X-ray minor axis (Hodge-Kluck+10)
Con:
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Winged FRIs exist
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However, inner FRIIs sometimes(/often?) present
(e.g., Saripalli+09)
+ more arguments (also Blundell: fading
argument?)
3C403
(Kraft et al. 2005)
Chandra ACIS-S
Courtesy Reynolds, Hodges-Kluck 2009
Optical/radio/X-ray orientations
Radio/opt in Winged galaxies
Main lobes
Wings
Hodges-Kluck+. (in prep)
Saripalli+09
Xs+wings relevant for (radio)
galaxy evolution?
• Merger rate: What fraction of winged RGs is due to
hydrodynamics?
– How can we isolate the X-shaped radio galaxies which are most
plausibly NOT due to hydrodynamic effects?:
• No opt/radio alignment ?
– 1/T_merger=Fraction(mergers)*fraction(winged)/T_winged
(Merritt+Ekers02)
• Standard evolutionary phase?: What makes a RG to become a
winged RG?
– Coincidental alignment of active jet with long-axis host/ISM/IGM
– X-ray ISM/IGM?: deep X-ray imaging required (not there yet?)
– grav. potential?: constrain triaxial shape of hosts of X-shaped radio
sources
– Accretion mode?: spectroscopy
– Why do X-shaped radio galaxies straddle the FRI/FRII boundary?
– Blow-out relevant for SF quenching?
Winged RG sample selection
• Eyeball inspection of FIRST survey of sources
with:
– Sensitivity to low-SBrightness features
• Dynamic range >40:1 (peak>5mJy/beam)
– Resolved structures
• R_maj>15arcsec and R_min > 5arcsec
• 1648 candidates:
– Bronze sample: 100 candidate wings,
– Silver sample: 50 quite certain
+ 14 known galaxies (2007)
– (WING/RG fraction ~4-10%)
Bronze sample
Spectroscopy for 53 of silver
sample in hand
Primary goal:
•Redshifts
•Emi-line fluxes
X=literature
O=new
Cheung,Landt,VK, Jordan+09
General sample properties
• Why do winged RGs straddle FRI/FRII
boundary?
Sneak preview
(aka very preliminary results)
Comparing Halpha
in 3CR and winged RGs
3CR from Buttiglione, Capetti+09
• No difference Normal / Winged RGs?
OIII/Hbeta ratio
3CR from Buttiglione, Capetti+09
Equivalent widths
Filled: NLR+BLR
Open: only NLR
• Unexpected high fraction of weak-lined sources?
FRI vs FRII
or
strong vs weak-lined?
Filled/open: strong/weak
Triangles: upper-limits OIII/OII
Conclusions
• X-shaped/winged RGs
– Get bit too little attention for their potential as probes
of RLAGN evolution / IGM+ISM properties
– Probably many due to hydrodynamics
– Multi-lambda demographics needed to go further
– >doubled (in 2007) the sample of winged RGs
• Cheung+ 2007, AJ, 133, 2097
– Spectra at hand, being analyzed
• Cheung, Landt, VK, Jordan, Healy, 2009, ApJS, 181, 548
• Landt, VK…., 2010 in preparation