Post on 20-Jan-2016
description
Winged and X-shaped radio galaxies
Gijs Verdoes KleijnOmegaCEN / 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)
OutlineOutline
Intro “winged” and X-shaped radio galaxies Observations and models/scenarios Are they important for understanding (radio) galaxy
evolution?
Sample Preliminary results
Intro “winged” and X-shaped radio galaxies Observations and models/scenarios Are they important for understanding (radio) galaxy
evolution?
Sample Preliminary results
Winged and X-shaped radio galaxiesWinged 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
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)
Winged radio galaxies, examples
NGC326; Ekers+78, Murgia+01
3C223.1; Dennett-Thorpe+02
From Reynolds+09
Mixed bag?
Formation modelsFormation models
Two classes of model1. Jet orientation fixed:
Jets energize active lobes Wings created by “blowout”
of the backflow (overpressure / buoyancy)
2. 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
Two classes of model1. Jet orientation fixed:
Jets energize active lobes Wings created by “blowout”
of the backflow (overpressure / buoyancy)
2. 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
See also Dennett-Thorpe et al. (2002), Merritt & Ekers (2002); Komossa (2003)
Scheuer (1974)
Hydrodynamical model favored?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?)
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?)
3C403(Kraft et al. 2005)
Chandra ACIS-S
Courtesy Reynolds, Hodges-Kluck 2009
Optical/radio/X-ray orientationsOptical/radio/X-ray orientations
Main lobesWings
Radio/opt in Winged galaxies
Saripalli+09
Hodges-Kluck+. (in prep)
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%)
Bro
nze
sam
ple
Spectroscopy for 53 of silver sample in hand
Primary goal:•Redshifts•Emi-line fluxes
General sample properties
• Why do winged RGs straddle FRI/FRII boundary?
Che
ung,
Land
t,V
K,
Jord
an+
09
X=literatureO=new
Sneak preview (aka very preliminary results)
Comparing Halpha in 3CR and winged RGs
• No difference Normal / Winged RGs?
3CR from Buttiglione, Capetti+09
OIII/Hbeta ratio3CR from Buttiglione, Capetti+09
Equivalent widths
• Unexpected high fraction of weak-lined sources?
Filled: NLR+BLROpen: only NLR
FRI vs FRII or
strong vs weak-lined?Filled/open: strong/weakTriangles: 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