1. Radio galaxies in the Chandra Era, Boston, July 2008 Shock heating in the group atmosphere of the radio galaxy B2 0838+32A Nazirah Jetha 1, Martin Hardcastle 2, Trevor Ponman 3, Irini Sakelliou 4 1 IRFU, CEA-Saclay, 2 University of Hertfordshire, 3 University of Birmingham, 4 MPIA-Heidelberg, Germany

2. Radio galaxies in the Chandra Era, Boston, July 2008 Radio Galaxy Heating Two major unresolved problems: –Similarity breaking -- groups and clusters follow scaling relations, but different from self- similar predictions. –Lack of very cold gas in group and galaxy cores Increasing evidence that radio galaxies can heat IGM RL RQ XMM RGs Croston et al. 2008 MNRAS 386 1709

3. Radio galaxies in the Chandra Era, Boston, July 2008 Radio Galaxy Heating On small scales, radio galaxies can heat via shocks generated by overpressured rapidly expanding lobes, e.g. Cen. A (Kraft et al 2003), NGC 3801 (Croston et al 2007). As radio source evolves, heat is transferred in different ways (Reynolds et al, 2002; Kraft et al, 2003; Nusser et al, 2006 ) Evidence to suggest that repeated cycles of radio galaxy heating have a significant effect (Croston et al, 2005; Jetha et al, 2007).

4. Radio galaxies in the Chandra Era, Boston, July 2008 Radio Galaxy Heating In order to explore effects of multiple cycles, wantsystems where more than one outburst can be studied simultaneously And ideally want systems: –Showing the ‘extremes’ of the AGN cycle –Sufficiently distant to study large scale IGM –Close enough to study small-scale shocks –‘Simple’ enough that effects of multiple outbursts can be disentangled.

5. Radio galaxies in the Chandra Era, Boston, July 2008 80kpc 1.4 GHz. (Jetha et al sub.) 0838+032 - Radio 2.5 kpc 85 ks Chandra observation to: Investigate potential shocks around small scale source. Examine effects of heating on large scale environment.

6. Radio galaxies in the Chandra Era, Boston, July 2008 0838+032 - X-ray SDSS OPTICAL 5 GHz VLA Chandra X-ray Host galaxy Companion galaxy Shock

7. Radio galaxies in the Chandra Era, Boston, July 2008 0838+032 - X-ray Group emission out to ~130 kpc Shock temperature: Mach number: Radius (kpc) 0.12130 Counts arcsec -2 100

8. Radio galaxies in the Chandra Era, Boston, July 2008 Timescales of the source Radius of inner lobes - 4.3 kpc Speed of sound in group - 330 km s -1 Age - 3.4 - 6.5 Myr Spectral age of outer lobes ~50 Myr Dynamic age, assuming lobes inflated in situ - 200 Myr Infer old lobes switched off ~150 Myr ago

9. Radio galaxies in the Chandra Era, Boston, July 2008 Feedback induced shocks? Central cooling time of gas - 170 Myr Comparable to time between old outburst switching off and new outburst switching on No indication in AGN spectrum for absorption from cold material to suggest merger (c.f. Cen. A, Kraft et al 2006; NGC 3801, Croston et al 2007)

10. Radio galaxies in the Chandra Era, Boston, July 2008 Energetics of inner lobes Mechanical power output of new source - (5.4 - 62) x 10 37 W No evidence for cold gas, so assume that AGN is accreting in hot-mode. Calculate Bondi power - P BONDI ~ 6 x 10 37 W Lower limit due to constraints on black hole mass and measuring density at Bondi radius.

11. Radio galaxies in the Chandra Era, Boston, July 2008 Energetics of outer lobes NW lobe is 130 kpc and S lobe is 190 kpc from centre Model lobes as ellipsoids with negligible initial volume inflated in situ Obtain pressure from density profile PdV work done on IGM - (2 - 4)x10 51 J Mean energy input rate - 3x10 35 - 3x10 36 W Bolometric X-ray luminosity (3.2±0.2)x10 35 W

12. Radio galaxies in the Chandra Era, Boston, July 2008 Implications for feedback models (1) Sufficient energy to counteract cooling Observations of lobes indicate delay in turning off cooling Due to time for energy/entropy to transfer to where needed Or time to drain accretion flow: –

13. Radio galaxies in the Chandra Era, Boston, July 2008 Implications for feedback models (2) What about to turn accretion on again? Central gas cooling time and time between outbursts is comparable Time taken for gas to cool may determine off time Clear that relationship between the two timescales determines duty cycles and on- times for any given system

14. Radio galaxies in the Chandra Era, Boston, July 2008 Conclusions 0838+32A - restarting radio source driving overpressured bubbles into IGM Old lobes have done sufficient work to counteract radiative cooling Young lobes driving a shock into IGM No evidence for merger to trigger new lobes Time delay in stopping accretion related to energy transfer/flow draining and microphysics of system First known system where strong shocks around young lobes are plausibly driven by hot-gas accretion (feedback)