Wavelet-based cross-correlation analysis of structure scaling in turbulent clouds

We propose a statistical tool to compare the scaling behaviour of turbulence in pairs of molecular cloud maps. Using artificial maps with well defined spatial properties, we calibrate the method and test its limitations to ultimately apply it to a set of observed maps. We develop the wavelet-based weighted cross-correlation (WWCC) method to study the relative contribution of structures of different sizes and their degree of correlation in two maps as a function of spatial scale, and the mutual displacement of structures in the molecular cloud maps. We test the WWCC for circular structures having a single prominent scale and fractal structures showing a self-similar behavior without prominent scales. Observational noise and a finite map size limit the scales where the cross-correlation coefficients and displacement vectors can be reliably measured. For fractal maps containing many structures on all scales, the limitation from the observational noise is negligible for signal-to-noise ratios >5. (abbrev). Application of the WWCC to the observed line maps of the giant molecular cloud G333 allows to add specific scale information to the results obtained earlier using the principle component analysis. It confirms the chemical and excitation similarity of $^{13}$CO and C$^{18}$O on all scales, but shows a deviation of HCN at scales of up to 7' (~7 pc). This can be interpreted as a chemical transition scale. The largest structures also show a systematic offset along the filament, probably due to a large-scale density gradient. The WWCC can compare correlated structures in different maps of molecular clouds identifying scales that represent structural changes such as chemical and phase transitions and prominent or enhanced dimensions.Comment: 26 pages, 41 figures, accepted to A&

Understanding the relationship between the environment of the black hole and the radio jet: optical spectroscopy of compact AGN

We aim to investigate the relationship between radio jet activity on parsec-scales and the characteristics of both the bright active galactic nuclei (AGN) and their broad line regions (BLR). For this purpose, we combine 2cm Very Long Baseline Array observations of AGN with their optical spectral observations. This would enable us to investigate the optical spectra of a set of 172 relativistically beamed, flat-spectrum AGN with the nuclear disk oriented near to the plane of sky. Here, we present first results from optical spectroscopic observations of the brightest AGN from the 2 cm VLBA survey, and show a diversity of their spectral morphologies.Comment: 2 pages, to be published in the Proceedings of "Multiwavelength AGN Surveys", Cozumel, Dec 8 - 12, 200

On the jet speeds of classical double radio sources

A simple integral relation is obtained for the distribution functions of jet speeds and jet-counterjet flux asymmetries of classical double radio sources. Analytic expressions relating the mean jet speed and the mean jet flux asymmetry, and their variances are derived. The results are considered in the light of orientation-based unified schemes, and an analytical equation for the critical angle separating quasars and radio galaxies is derived. The mean jet speeds of classical double radio sources are estimated using the asymmetry of jet-counterjet flux densities taken from the 3CRR and B2 samples. For FRI radio sources the mean jet speed is ~0.54c (with a standard error SE=0.03c), while for FRII low-redshift radio galaxies and intermediate redshift quasars the values found are ~0.4c (SE=0.06c) and >0.6c respectively.Comment: 7 pages, 2 figures. The revised version is accepted for publication in the MNRA