X-shaped Radio Galaxies

What do

have to say aboutRadio-Mode Feedback?

Edmund Hodges-Kluck

Clusters & Groups in the Chandra Era

Chris Reynolds (UMd), Teddy Cheung (NRL), Cole Miller (UMd), Marc Pound (UMd)

What are X-shaped Radio Galaxies?The origin of XRGs

XRGs and Ghost Cavities

Agenda

What are X-shaped Radio Galaxies?

X-shaped Radio Galaxies (~5% of RGs)

“Normal” Double-Lobed (FR II) Radio Galaxies

Lobes

Hot Spots

Jets

Long, Inactive Lobes (Leahy+84)

Centro-symmetric (Leahy+84)

Weak FR IIs/Strong FR Is (Cheung+09)

Higher than average SMBH masses

(Mezcua+10)

Possibly related to “winged” RGs

(Cheung 07)

Jets co-aligned with host major axis

(Capetti+02)

What are X-shaped Radio Galaxies?The origin of XRGs

XRGs and Ghost Cavities

1. Fossil Relics

• Precession (Dennett-Thorpe+02)

• SMBH merger (Merritt+02)

• Accretion torque (Rees+82)

2. Redirected Lobes

• Buoyant Backflow (Worrall+95, Leahy+84)

• Overpressured Cocoon (Capetti+02)

3. Binary AGN

• Twin jet pairs (Lal+Rao 05)

Radio lobes are bubbles in a tenuous, hot (T > 107 K) plasma

If jets/lobes interact with surroundings, it will be with the IGM/ICM

RadioX-ray

Do the data support a rolefor XRG environments?

X-ray Imaging

Is the hydrodynamichypothesis plausible?

Hydrodynamic Simulations

ISM

IGM

ΔPA = 0 Coaligned with major axis

ΔPA = 90 Coaligned with minor axis

Hodges-Kluck+2010a ApJ…710.1205

Hodges-Kluck+Reynolds 2011ApJ…733…58

X-ray observations and hydrodynamic simulations support a role for XRG environments

Unclear whether proposed hydrodynamic models really work

At least one XRG looks like a spin-flip: 4C +00.58 (Hodges-Kluck+2010b ApJ…717..L37)

Review: Gopal-Krishna+2010 arXiv/1008.0789

What are X-shaped Radio Galaxies?The origin of XRGs

XRGs and Ghost Cavities

What Happens to Dead Radio Galaxies?

Ghost cavities reported in a number of systems

(e.g. Perseus, NGC 741, A2597)

Cavities ubiquitous in groups; little correlation with radio

emission (Dong+10), but only seen near cores (c.f.

Giacintucci+11)

Cavity evolution poorly understood

How do radio galaxies heat cores?

• PdV energy in cavities vs. jet-driven shocks (e.g. Reynolds+02), disk winds (e.g. Gaspari+11)• Maybe they don’t directly? Hybrid conduction models; Stirring (Ruszkowski+Oh 2010)

Inactive Lobes

• Long (up to >100 kpc)

• Usually in groups

• Either fossils or evolve in response to environment

• Presumably have cavities

• Bright at 1.4 GHz

100 kpc

Only 2 XRGs have X-ray exposures of ~100ks:

Both have significant cavities associated with wings (highlighted in unsharp mask images)

Chip Edge

Jet

Proof of concept: NGC 326

The east wing cavity is ~100 kpc from the core and is probably over 50 Myr old

The active outburst may itself be associated with cavities and a shock front…

0.3-3 keV

3-8 keV

kT (apec 1-T 0.3-5 keV) Surface Brightness

1. Temperature does not follow surface brightness

2. Density, temperature changes behind front consistent with Mach ~2 shock

Unsharp MaskRaw 0.3-5 keV binned 16x

What can we know?

• Age from several avenues

• Rough size/energy

• Gross magnetic structure (Murgia+01)

• T/P of surrounding gas

What can’t we know (yet)?

• Filling factor/entrainment

• Cap of material?

• Old shocks/sound waves?

• Bubble shredding?

• Detailed synchrotron map

Need higher S/N!

XRGs are an interesting subclass of double-lobed radio galaxies whose origin is mysteriousXRGs illuminate hard-to-find “dead” radio bubbles far from the AGN

Higher S/N required to study cavities (XMM? Astro-H?)

Summary

3C 388

3C 305

3C 264

3C 171

3C 465

3C 272.1

3C 120

Jet Axis

False Synchrotron (GHz)

Old cavities re-energized by restarted AGN in hydro simulations

Wing length as a function of atmosphere

parameters

Wing length as a function of jet parameters

4C +00.58

Radio jet aligned with host minor axis, wings very long relative to cocoon

OpticalRadio

Case in Point: 4C +00.58

Optical

X-ray unsharp mask

“Stellar shell” suggests recent minor galaxy merger

X-ray cavities aligned with wings and major axis suggest recent jet activity along other axes

Long wings preclude hydrodynamic deflection—they must be fewer than 40 Myr old

Case in Point: 4C +00.58

~ 1.6

~ 0.6

The bent jet, seen in radio (VLA + CARMA) and X-ray (Chandra), appears to be cooling rapidly at the tip: has it been dragged?

Hypothesis: A minor merger activated the radio galaxy along one axis, then accretion torque or coalescence of a SMBH binary moved the jet.

Case in Point: 4C +00.58

Model Testing with Timescales Minimum wing age (transonic expansion)

Maximum Cocoon Age (transonic expansion)

Synchrotron cooling time (wing decay)

X-ray free-free (cavity wall) cooling time500~

)(2

5

Tn

nkT

E

Et ff

40~22

34

2

BT

esync Uc

cm

E

Et

90~expsc

lt Myr (measured from X-rays,

radio)

Myr (measured from radio)

Myr (measured from X-rays)

35~expsc

lt Myr (measured from X-rays,

radio)

Transonic expansion time

(minimum age): texp ~ lwing/cs~ 90 Myr

tsync ~ 40 Myr [1 GHz] Cocoon should expand

faster than wings, and cs is constant in the region—strong projection ruled out by OII/OIII ratio

Cocoon is well defined

Cocoon texp < 35 Myr Cavities misaligned with

the jets unexplained

Did the wings form hydrodynamically?

SDSS r+g

Timescales Sound speed (pressure crossing time)

Temperature and emission-weighted density from apec fits to the 0.3-3 keV spectrum in Xspec

kT ~ 1.0 keV within 40 kpc (approximately isothermal)

Synchrotron (wing) cooling time

Equipartition B-field assumed; use radio flux and volume of wings/lobes, with spectral index (~0.7) determined from photometry

With B in hand, synchrotron frequency measured at 1.4 GHz, so wing lifetime is for electrons radiating at 1.4 GHz

40~22

34

2

BT

esync Uc

cm

E

Et

400~

kTcs km/s

Myr (measured from radio)

Timescales X-ray free-free (cavity wall) cooling time

Temperature and emission-weighted density from apec fits to the 0.3-3 keV cavity wall spectrum in Xspec

Assume a typical bremsstrahlung cooling function (T0.5)

Maximum Cocoon Age (transonic expansion)

Cocoons associated with bow shocks, powerful jets, so supersonic expansion (several times ambient sound speed) assumed even in weaker radio galaxies

Trans- or sub-sonic expansion unlikely to produce a cocoon, but possibly intermittent jets…

500~)(2

5

Tn

nkT

E

Et ff

Myr (measured from X-rays)

35~expsc

lt Myr (measured from X-rays,

radio)