A statistical analysis of position angle differences (∆PA) between smalland large-scale structures of EGRETdetected AGNs has been made. The results show that γ-ray quasars have the alignment of radio jets, while γ-ray BL Lac objects have large∆PA. This may contribute to a better understanding of different blazar types and of the AGN unification scheme.

Here we present some critical discussions about the systematic uncertainty by dust extinction in the recent cosmological results of high-redshift Type Ia supernovae. First we argue that the currently available data do not robustly exclude the cosmologically significant extinction either by the reddening check or the dispersion argument because of the observational uncertainties, even in the cas...

We present observations of a sample of optically-faint, hard X-ray sources of the kind likely to be responsible for much of the hard X-ray background. We confirm that such sources are easily detected in the near-infrared, and find that they have a featureless continuum suggesting that the active nucleus is heavily obscured. The infrared colours of the majority of the targets observed are consis...

We present the first submillimetre observations of the z=2.36 broad absorption line system Hawaii 167. Our observations confirm the hypothesis that Hawaii 167 contains a massive quantity of dust, the optical depth of which is sufficient to completely extinguish our ultraviolet view of a central, buried quasar. Hawaii 167’s submillimetre luminosity and associated dust mass are similar to the ult...

We present a simple population synthesis scheme which recognizes composite starburst+Seyfert 2 nuclei from a few easy-to-obtain optical measurements. Composite systems seem to evolve towards less luminous Seyfert 2’s which do not harbor detectable circum-nuclear starbursts. We encourage applications of this cheap diagnostic tool to large samples of Seyfert 2’s, as well as its extension to other...

We study the appearance of ντ from active galactic nuclei (AGN) through neutrino spin-flip. We consider two situations: i) Spin (flavour)-precession in a reasonable strength of magnetic field in AGN, BAGN ii) Adiabatically resonant conversions caused by an interplay of BAGN and the violation of equivalence principle. Observational consequences for both situations are discussed.

The four-image gravitational lens system MG 0414+0534 was observed with the GHz images reveal structure in the components which is consistent with that seen at other wavelengths. There was no detection of other extended emission, nor were there detections of the lensing galaxy or the " component x " seen in optical images. Detections of polarized emission show that the fractional polarized inte...

The evidence for obscured AGN and in particular for obscured quasars is discussed. The spectrum and source modelling of the X-ray Background suggests that most massive black holes grow by obscured accretion. A possible major growth phase which is Compton thick is explored and shown to be difficult to detect directly with current instruments .

We calculated the median values of the following parameters for 87 groups of galaxies with three to eight components: the mean rms velocity of the galaxies in the group, Sv = 166 km/s; the harmonic mean radius, Rh = 29 kpc; and the mass-to-light ratio, Mvir/L = 33M⊙/L⊙. The Mvir/L ratio depends on the population of the system, while Sv does not depend on Rh. To ascertain the relationship betwee...