Large-scale Jets in DRAGNs J. P. Leahy Jodrell Bank Observatory, University of Manchester (Thanks to NRAO for financial support) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 DRAGNs Radio sources powered by jets from AGN: Radio Galaxies, Quasars Seyfert galaxies etc. Relativistic (initial) flow speeds: Lorentz factor  ~ 3-10. This talk will focus on the more powerful examples, I.e. radio galaxies & quasars. Yes it’s an acronym. A. Bridle et al./NRAO AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Questions How are DRAGNs born? How stable are the jets? How long do DRAGNs live? How do they die? Is there an after-life? AAS Meeting Wednesday 5th June 2002

Activity Power Spectrum ??? Structure of lobes Structure in jets Direct Observations Crude representation: intermittancy, i.e. phase correlated. Peak around 30 Myr corresponds to overall life time. Different observational approaches give us different windows on this function. AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 2353+495 Switch-on Smallest DRAGNs have dynamical ages D/v ~ 500 yrs from measured hotspot advance Owsianik & Conway (1998a,b) Start-up time ~ 1 Million times shorter than galaxy merger timescale, O(108) yrs On larger scales we can’t do this: we only see a single instant. Actually not quite true, as we’ll see. Like explaining why you are late for work by blaming the transition from barbarian society to civilisation. (Courtesy G. Taylor) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Pointing Stability 4.6 Mpc Orientation can be stable for 0(108) yr: straightness of some Giant DRAGNs. Expansion speed <0.1c from symmetry statistics (Scheuer 1995) BH spin aligns with accreted material in 105-107 yrs:  stability due to stable accretion (Natarajan & Pringle 1998) Mack et al. (1996) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Winged DRAGNs Multiple outbursts revealed by change of jet axis. Few % of powerful DRAGNs What happens if axis does not change? 500 kpc Multiple orientations imply multiple accretion events, I.e. multiple outbursts, even if the events follow each other quite rapidly as implied by lack of spectrally aged material in some winged dragns, e.g. Dennett-Thorpe et al. (2002). 300 kpc AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Bottleneck Lobes Can get similar structures (not as extreme as in 3C132 from what I’ve seen) from steady jet simulations, due to interactions between jet and eddies in the backflow. So not definitive, but suggestive. 50 kpc 500 kpc AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 3C390.3 At  26° to line of sight Twin-peak Balmer lines (Eracleous & Halpern 1994) Superluminal motion (Alef et al. 1996) Overlapping lobes  Extends  0.5 Mpc along line of sight  Near side (NW) seen 1.8 Myrs more developed: Bottleneck More expanded hotspot 265 kpc (projected) Leahy & Perley (1995) Angle from fitting balmer lines to disk model. AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Power Stability Hotspots in 80-90% of lobes in powerful DRAGNs  jets nearly always “on”. Hotspot:lobe flux ratio: Median 0.22 IQR 0.11 – 0.54 Jets could fluctuate in power by factors of several. Best seen as limit to AGN fluctuation, as hotspot structures will fluctuate substantially due to fluid dynamic effects if the simulations are to be believed. Caveats: “Hotspot” defined as flux within 5% of lobe size, ie scaled to overall size of source. Not the finest scale structure, so some short-term fluctuations averaged out. From Atlas of DRAGNs (Leahy, Bridle & Strom 1996) AAS Meeting Wednesday 5th June 2002

Re-invigorated Jets: 3C 33.1 VLA A+B+C+D 20 cm 1.5 Side shocks indicate pre-existing jet cavity is expanding into the lobe. No shock ahead of high-pressure plug shows there is still a jet flow ahead, but with a lower emissivity and presumably pressure. Note there is still a hotspot in this lobe. 200 kpc AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Hercules A Powerful DRAGN in cluster-dominating galaxy at z= 0.154. X-ray parameters typical of Abell clusters. Cluster elongated along radio axis. 400 kpc Gizani & Leahy (in preparation) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 VLA B+C+D 3.6 cm 0.74 beam AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 VLA A+B+C+D 6.1 cm 0.36 AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 J. Morse, STScI A. Rosen et al. (1999, ApJ) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Spectral Index 1.5 – 5 GHz AAS Meeting Wednesday 5th June 2002

Understanding the “Rings” Present in both lobes Surround jet features Spectrally young Brighter on outer side Brighter in West lobe Jets: brighter jet is nearer, from depolarization. Inclination i  50° Model: Jet asymmetry due to beaming:  cos i  0.5 Observed timescales 3x different in the two lobes, from light-travel effect. Rings are shocks in old lobes caused by new outburst Fluctuations on many timescales AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 VLA B+C+D 3.6 cm 0.74 0.9 Myr 2.7 Myr AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Double-Double DRAGNs 1 Mpc Prevalence of Double Double structure in Giant radio galaxies suggests larger-amplitude fluctuations on long timescales. Many inner doubles needed to build up outer double. 1 Mpc Schoenmakers et al. (2000) Saripalli et al. (2002) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 PKS 1637-77 ATCA 12 cm 2.9 ATCA 22 cm 6.4 200 kpc Leahy & Killeen (in preparation) AAS Meeting Wednesday 5th June 2002

Crossing the F-R Divide Plume best explained as a remnant of previous FR I phase. Luminosity of PKS1637-77: P178  1025 W Hz-1sr-1 (near FR divide). Luminosity of plume: ~1023 W Hz-1sr-1 Characteristic of fainter FR I sources. NB: remnant would be hard to see, if new FRII phase was much brighter. AAS Meeting Wednesday 5th June 2002

Crossing the F-R Divide Another case: PKS2104-25N Cameron et al. (1988) Bicknell, Cameron & Gingold (1990) High resolution: Clear FR II With plume 50 kpc AAS Meeting Wednesday 5th June 2002

Crossing the F-R Divide Another case: PKS2104-25N Cameron et al. (1988) Bicknell, Cameron & Gingold (1990) Low resolution: Plumes form wide-angle tail. 500 kpc AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Death of DRAGNs Powerful DRAGNs have synchrotron age  10 Myr typical lifetime ~20 Myr Few DRAGNs are bigger than 1 Mpc: Expansion speed ~0.1c  Max age ~16 Myr? Jet shutdown: Hotspots expand, fade should leave diffuse lobes intact Fade by synchrotron ageing on ~ 108 yr timescale. AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Dying DRAGNs? Relaxed steep-spectrum DRAGNs should be more common than “Classical” Doubles. Actually <10% Van der Laan (1969): Age  (Break frequency)-1/2 Detectable if   B Survey at  should mostly find DRAGNs with   B Not so! van Breugel & Fomalont (1984) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Ghost DRAGNs? If radio-quiet cavities in clusters are aged relic lobes (e.g. Enßlin 1999), where are the cases visible only in low-frequency images? Abell 2597 (McNamara et al. 2001) AAS Meeting Wednesday 5th June 2002

AAS Meeting Wednesday 5th June 2002 Conclusions Jets show large-amplitude variability on many timescales. with light-travel effects, will disguise intrinsic symmetry. Multiple outbursts can dramatically affect large-scale structure of DRAGNs. End-point of DRAGN lifecycles poorly understood. AAS Meeting Wednesday 5th June 2002