The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) et al. ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) + VLBA + VLA + MERLIN + ARCHIVES ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) + VLBA + VLA + MERLIN + ARCHIVES ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) + VLBA + VLA + MERLIN + ARCHIVES ultra-fast

The quasar PKS : Direct evidence for a changing orientation of the central engine. John Wardle (Brandeis), Dan Homan (NRAO), C. C. Cheung & Dave Roberts (Brandeis) + VLBA + VLA + MERLIN + ARCHIVES ultra-fast

Properties Gamma-ray blazar (EGRET) X-ray variable (RXTE, Marscher)    m opt > 5.4 m (Harvard plates, Liller) Redshift = 0.360; 1 mas = 5.0 pc (h=0.7) These are characteristics of highly relativistic jets that make a small angle to the line of sight. They should also exhibit superluminal motion.

Jan-Dec 1996, 15 GHz

 = 1.0 mas/yr at 22, 15 and 5 GHz

Properties Gamma-ray blazar (EGRET) X-ray variable (RXTE, Marscher)  m opt > 5.4 m (Harvard plates, Liller) Redshift = 0.360; 1 mas = 5.0 pc (h=0.7)   app = 20   pattern > 20   line of sight ~ 1/20 rad ~ 3 o

The alignment of small and large scale structure  P.A. of parsec scale jet = -28 o

5 GHz VLA image

The misalignment of small and large scale srtructure  P.A. of parsec scale jet = -28 o P.A. of kiloparsec scale jet = 155 o The pc and kpc jets differ in direction on the sky by 177 o. This is the most extreme misalignment known.

Questions  Is the parsec scale jet a new jet?  Or, do the pc and kpc jets join up?  If so, how and where? Does the change in jet direction represent a deflection or fluid instability in the jet itself, on parsec or sub-parsec scales, or has the axis of the central engine changed? We need low resolution VLBA observations

at 1.4 GHz

at 1.4 GHz, smoothed

Feature at 300 mas is not a hotspot at the end of a new jet. If the highly polarized edge is a shock (terminal hotspot), then the total intensity should peak there too. The jet makes an angle ~ 3 o to the line of sight, so the “hot spot” is viewed almost face-on (since v hotspot < v jet ). So if the hotspot were a Laing sheet perpendicular to the jet, it could not exhibit ~70% polarization.

on three scales

explanation

Where is the counter- lobe? In projection, on the same side of the core as the VLA jet, and opposite the VLBA jet

Behind the jet?

Here it is core vla jet

New interpretation

Inferred timescale The rate at which the axis turns, , can be inferred from the turning point in the jet at 300 mas (1500 pc), and the observed superluminal motion. If the fluid motion is ballistic at  = 20, then 1/  ~ 10 4 years. If, more realistically, the fluid pushes the jet outwards at an effective speed  c, then 1/  ~ 4 x 10 6 years.

Realignment timescale If a rotating black hole and its accretion disk are misaligned (galaxy merger?), they realign via Lense-Thirring drag (Bardeen & Petterson, 1975). The time scale for this is relatively fast (Natarajan & Pringle, 1998, Dennett- Thorpe et al 2002) t align (yr) = 3.6 x 10 4 a 11/16 (  /0.01) 13/8 x (  L E /L) 7/8 M 8 –1/16

1.4 – 5 GHz spectral index map: the VLA jet is still populated by recently accelerated electrons

x-rays by Rita Sambruna (false color) superposed on radio (contours)

Conclusions PKS is an extreme blazar in all wavebands. (  app = 20 and  los ~3 o ) On parsec scales, the jet points to the north-west The jet turns back across the line of sight at 300 mas, and feeds the south-eastern kpc jet. A counter-lobe has been found north-west of the core. The data suggest that the axis of the central engine has changed by ~20 o relatively recently, perhaps due to a black hole merger.

nrl