Tracing the merger-driven evolution of active galaxies using the CJF sample

In the context of the evolution of large structures in the Universe, it is unclear whether active galaxies are a phase which each galaxy undergoes, and what is the importance of the evolution of black holes in their centers. Binary black hole (BBH) systems could play a key role in our understanding of the above question. We investigate the Caltech-Jodrell Bank flat-spectrum (CJF) sample for evidence in favor of the merger-driven evolution scheme of active galaxies and search tracer-systems of AGN evolution and possible indications of BBH candidates. We discuss the validity and ambiguity of such indications and formulate a set of selection criteria for the detection of such systems. We conduct an extensive literature search for all available multi-wavelength information, concentrating on the optical and infrared regime, in addition to morphological information of the CJF sources. We analyze the statistics of this sample, in terms of these properties. We find 1 ULIRG (Mrk 231) included in the CJF, prototype of a transitory system. In total 28.6% of the CJF sources with z<0.4 are distorted or have a companion. Given the unbiased sample used here, this provides strong evidence for the ubiquity of the merger phenomenon in the context of active galaxies. We find a correlation between the radio and the near-infrared luminosity for the high-luminosity sources, interpreted in the context of the interplay between a star-formation and AGN component. We find a connection between variability and evolutionary transitory systems, as selected through their near-infrared colors. We select 28 sources that trace the different evolution phases of an AGN, as well as a number of the most promising BBH candidates. We find 4 sources with almost periodical variability in the optical and radio on similar timescales.Comment: 18 pages, 6 figures, accepted for publication in A&A (updated to match proofs

A Global 86GHz VLBI Survey of Compact Radio Sources

We present results from a large 86GHz global VLBI survey of compact radio sources. The main goal of the survey is to increase by factors of 3--5 the total number of objects accessible for future 3-mm VLBI imaging. The survey observations reach the baseline sensitivity of 0.1Jy and image sensitivity of better than 10 mJy/beam. The total of 127 compact radio sources have been observed. The observations have yielded images for 109 sources, extending the database of the sources imaged at 86GHz with VLBI observation by a factor of 5, and only 6 sources have not been detected. The remaining 12 objects have been detected but could not be imaged due to insufficient closure phase information. Radio galaxies are less compact than quasars and BL Lacs on sub-milliarcsecond scale. Flux densities and sizes of core and jet components of all imaged sources have been estimated using Gaussian model fitting. From these measurements, brightness temperatures have been calculated, taking into account resolution limits of the data. The cores of 70% of the imaged sources are resolved. The core brightness temperatures of the sources peak at $\sim 10^{11}$ K and only 1% have brightness temperatures higher than $10^{12}$ K. Cores of Intraday Variable (IDV) sources are smaller in angular size than non-IDV sources, and so yield higher brightness temperatures.Comment: 72 pages, 12 figures, accepted for publication in the Astronomical Journa