The Megaparsec-Scale X-ray Jet of the BL Lac Object OJ287

We present an X-ray image of the BL Lacertae object OJ287 revealing a long jet, curved by 55 degrees and extending 20", or 90 kpc from the nucleus. This de-projects to >1 Mpc based on the viewing angle on parsec scales. Radio emission follows the general X-ray morphology but extends even farther from the nucleus. The upper limit to the isotropic radio luminosity, ~2E24 W/Hz, places the source in the Fanaroff-Riley 1 (FR 1) class, as expected for BL Lac objects. The spectral energy distribution indicates that the extended X-ray emission is from inverse Compton scattering of cosmic microwave background photons. In this case, the derived magnetic field is B ~ 5 microGauss, the minimum electron energy is 7-40 m_e c^2, and the Doppler factor is delta ~ 8 in a knot 8" from the nucleus. The minimum total kinetic power of the jet is 1-2E45 erg/s. Upstream of the bend, the width of the X-ray emission in the jet is about half the projected distance from the nucleus. This implies that the highly relativistic bulk motion is not limited to an extremely thin spine, as has been proposed previously for FR 1 sources. The bending of the jet, the deceleration of the flow from parsec to kiloparsec scales, and the knotty structure can all be caused by standing shocks inclined by ~7 degrees to the jet axis. Moving shocks resulting from major changes in the flow properties can also reproduce the knotty structure, but such a model does not explain as many of the observational details.Comment: Accepted for publication in the Astrophysical Journa

Collective Evidence for Inverse Compton Emission from External Photons in High-Power Blazars

We present the first collective evidence that Fermi-detected jets of high kinetic power (L_kin) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L_kin > 10^45.5 erg s^{-1}) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self Compton (SSC) emission. For the lowest power jets (L_kin < 10^43.5 erg s^{-1}), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed (Kharb et al. 2010), this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.Comment: Accepted for Publication in ApJ Letters, 5 pages, 4 figure

Modeling the time-dependent polarization of blazars

Linear polarization is an extremely valuable observational tool for probing the dynamic physical conditions of blazar jets. Some patterns are seen in the data, suggestive of order that can be explained by shock waves and helical magnetic field components. However, much disorder is apparent, which implies that turbulence plays a major role as well, especially in the fluctuations of flux and polarization, and perhaps particle acceleration. Here, we present some actual flux and polarization versus time data, plus simulations of model jets. We analyze the output of the simulations in a manner that can be compared with observational data. The results suggest that the ratio of turbulent to ordered magnetic fields varies with time.AST-1615796 - National Science Foundation; NASA; NNX14AQ58G; NNX15AR45

Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behavior rules out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow; perhaps related to turbulence in the accretion disk; coupled with hydrodynamic instabilities, leads to the non-ballistic dynamics that cause the observed non-periodic changes in the direction of the inner jet.Comment: Accepted for Publication in The Astrophysical Journal. 11 pages, 6 figures, 4 tables. High resolution images on figure 1 and complete tables 1 and 2 may be provided on reques