Global Jet Watch

Abstract:

We have studied the FRI radio galaxy NGC 6251 and its environment at several wavelengths and scale lengths. On the large scale, we have probed the gravity field by measuring the velocity dispersion of the cluster members associated with NGC 6251 and relating this to, the cluster's X-ray emission. On the small scale, the gravitational information is provided by cold HI near the nucleus and the distribution of stars and gas near the centre of the galaxy. The cold HI gas which we have measured explains the absorption of the central X-ray emission and is consistent with the extinction through the recently discovered HST gas disc of NGC 6251.

Abstract:

The superior spatial resolution of the Chandra X-ray Observatory is sharpening our X-ray vision of extragalactic radio sources. Our recent Guest Observer observations of a small sample of B2 radio galaxies show jet X-ray emission to be common in low-power radio galaxies, whereas previously such jets were only X-ray detected in nearby Cen A and M 87. At high redshift, Chandra clearly separates AGN-related emission from the surrounding X-ray emitting cluster medium, as illustrated by our results for 3C 220.1 at a redshift of 0.6.

Abstract:

We perform a series of so-called "synthetic observations" on a set of 3D MHD jet simulations which explicitly include energy-dependent transport of relativistic electrons, as described in the companion paper by Jones, Tregillis & Ryu. Analyzing them in light of the complex source dynamics and energetic particle distributions described in that paper, we find that the standard model for radiative aging in radio galaxies does not always adequately reflect the detailed source structure.

Abstract:

Numerical modelling is performed for extreme relativistic parallel shocks with upstream Lorentz factors Gamma = 50. Assuming that the scattering is either large-angle or over pitch angles > Gamma(-1), spectral flattening and shock acceleration speed-up is found. The energy gain per cycle is similar to Gamma(2). The likely output from relativistic shocks due to the infall from the accretion disc to the AGN black hole is computed. Neutrinos from proton-gamma interactions may be detectable with planned neutrino telescopes but the gamma-ray output may contribute only 1/100th of the observed flux of 3C 273.

Abstract:

A small fraction of double radio sources show a peculiar and striking hybrid morphology; they have a distinctly FRI structure on one side of the nucleus, and a FRII structure on the other. We argue that the mere existence of these HYMORS is quite incompatible with the theoretical explanations for the Fanaxoff-Riley dichotomy that are based upon the nature of the jet plasma, or those invoking an intrinsic property of the central engine. Rather, these HYMORS strongly support models that explain the difference between FRI and FRII sources in terms of asymmetry of interaction of the jets with the external environments. We further show that a model for radio source dynamics we had earlier proposed can neatly reproduce the observed dependence of the radio power dividing the two FR classes on the optical luminosity of the host galaxy, as found by Owen & White and Ledlow Owen.