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Winged and X-shaped radio galaxies

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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Winged and X-shaped radio galaxies

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  1. 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)

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

  3. 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)

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

  5. 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)

  6. 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?)

  7. 3C403 (Kraft et al. 2005) Chandra ACIS-S Courtesy Reynolds, Hodges-Kluck 2009

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

  9. 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?

  10. 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%)

  11. Bronze sample

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

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

  14. Sneak preview (aka very preliminary results)

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

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

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

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

  19. 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

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