XMM results in radio-galaxy

physicsJudith Croston

CEA Saclay, Service d’Astrophysique

EPIC consortium meeting, Ringberg, 12/04/05

In collaboration with:

• Martin Hardcastle (Hertfordshire)• Mark Birkinshaw, Diana Worrall,

Elena Belsole, Dan Evans (Bristol)• Dan Harris (CfA)

Radio-galaxy morphologies

Outstanding problems• Magnetic field strengths: can’t be directly

measured from radio synchrotron emission, so equipartition ( min. total energy) commonly assumed

• Particle content: electron-positron or electron-proton?

• Dynamics: – FRIs: missing pressure?– FRIIs: supersonic or not?

Solving these problems is essential to understanding radio-galaxy impact in groups and clusters.

Radio galaxies in X-rays• Jets and hotspots (typically need Chandra

resolution)• Radio lobes:

– Non-thermal emission via inverse Compton scattering

– Seed photons from CMBR, AGN nucleus and SSC– Measure internal energy density, magnetic field

strengths– Infer particle content

• Environments: – Radio galaxies are found in groups and clusters– Measure external density and pressure– Comparison with internal radio-lobe properties to

study jet and lobe dynamics.– Temperature structure => heating

XMM observations of IC emission from

FRII lobes

3C 284, z=0.25

3C 223z=0.14

• Lobe emission from two nearby FRIIs (Croston et al. 2004, MNRAS 353 879)

• IC scattering of CMB; B ~ Beq

• Belsole et al. (2004) found similar results for three high-z FRIIs observed with XMM.

• Grandi et al. (2003) detected lobe emission from Pic A – origin may be thermal or IC.

Chandra and XMM study(Croston et al. 2005, ApJ in press, astro-

ph/0503203)• Sample of 33 radio galaxies

observed by Chandra and XMM.

• Lobe emission from 75% of sources.

• Magnetic fields between (0.3 – 1.3) Beq, with peak at

B ~ 0.7 Beq.

• Internal energy always within a factor of two of minimum value.

• Energetically dominant proton population unlikely.

XMM observations of environments

3C 449

3C 66B

Croston et al. 2003 MNRAS 346 1041; 2005 MNRAS 357 279, and Evans et al. 2005 MNRAS, in press, astro-ph/0502183)

• FRI environments show:– SB deficits at radio lobes– Dense environments = large,

rounded lobes– Less dense = narrow plumes– Heating (see later)

Dynamics and particle content in FRIs

• XMM confirms Einstein/ROSAT results for FRIs: Pext >> Pint(equipartition)

extra particle content/departure from equipartition.

• IC upper limit rules out electron domination to provide additional pressure.

• Thermal upper limit rules out entrained gas with Tenv .

• Heated, entrained material (T ~ 3 – 5 keV) most plausible.

• Relativistic protons possible, but need p/e ~ 200.

• Also detected with XMM:– Groups rather

than clusters– No evidence

for shock-heating

– Pext ~ Pint (measured from IC)

=> Not supersonically expanding?

FRII environments

XMM detects shock heating

• XMM and Chandra observations show radio-lobe shock heating of the X-ray environment from the small-scale lobes of Cen A (Kraft et al. 2003).

(pictures from Kraft et al. 2003)

AGN in cooling flows • M87 has thermal sub-

structure associated with radio lobes (e.g. Belsole et al. 2001).

• Is temperature structure consistent with models for counteracting cooling flows (e.g. Molendi 2002, Kaiser 2003, Ghizzardi et al. 2004)?

=> AGN energy input (rising bubbles/mixing) can balance cooling and produces multi-phase medium.

Extended heating in FRI atmospheres

• XMM-observed RG environments significantly hotter than LX/TX prediction.

• ROSAT study:– RL groups hotter

than RQ groups of the same luminosity.

– 50% of E-dominated groups (= X-ray bright) are RL. (Croston et al. 2005, MNRAS,

357 279)

Ongoing projects with XMM

• Inner jet dynamics– Testing jet models (Laing & Bridle 2002) by measuring

environmental properties.– Investigating role of environment in producing stable

jets.

• FRI environments– Completing sample that includes all common

morphologies to understand jet/environment interactions in whole population.

• Archive study of heating– Large fraction of ROSAT sample now observed by XMM.– Follow up heating study with better Lx and Tx constraints,

detailed study of gas distribution in radio-loud and quiet groups.