2. 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)

3. Outline Intro “winged” and X-shaped radio galaxies Sample
Observations and models/scenarios
Are they important for understanding (radio) galaxy evolution?
Sample
Preliminary results

4. Winged and X-shaped radio galaxies
Winged population ~7-10% of 3CR radio galaxy population (Leahy & Williams 1984)
Radio morphology
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 X-shape
3C403 (Kraft et al. 2005)

5. Winged radio galaxies, examples
NGC326;
Ekers+78, Murgia+01
3C223.1; Dennett-Thorpe+02
Mixed bag?
From Reynolds+09

6. Formation models Two classes of model Jet orientation fixed:
Jets energize active lobes
Wings created by “blowout” of the backflow (overpressure / buoyancy)
Jet re-orientation:
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)

7. Hydrodynamical model favored?
Pro:
Wings roughly align with optical (Capetti+02) and X-ray minor axis (Hodge-Kluck+10)
Con:
Winged FRIs exist
However, inner FRIIs sometimes(/often?) present (e.g., Saripalli+09)
+ more arguments (also Blundell: fading argument?)

8. 3C403 (Kraft et al. 2005) Courtesy Reynolds, Hodges-Kluck 2009
Chandra ACIS-S
Courtesy Reynolds, Hodges-Kluck 2009

9. Optical/radio/X-ray orientations
Radio/opt in Winged galaxies
Main lobes
Wings
Hodges-Kluck+. (in prep)
Saripalli+09

10. 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?

11. 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%)

12. Bronze sample

13. Spectroscopy for 53 of silver sample in hand
Primary goal:
Redshifts
Emi-line fluxes

14. General sample properties
Cheung,Landt,VK, Jordan+09
X=literature
O=new
Why do winged RGs straddle FRI/FRII boundary?

15. Sneak preview (aka very preliminary results)

16. Comparing Halpha in 3CR and winged RGs
3CR from Buttiglione, Capetti+09
No difference Normal / Winged RGs?

17. OIII/Hbeta ratio
3CR from Buttiglione, Capetti+09

18. Equivalent widths Unexpected high fraction of weak-lined sources?
Filled: NLR+BLR
Open: only NLR
Unexpected high fraction of weak-lined sources?

19. FRI vs FRII or strong vs weak-lined?
Filled/open: strong/weak
Triangles: upper-limits OIII/OII

20. 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