A multi-wavelength study of the evolution and pc-scale jet kinematics of active galaxies

Active galaxies have been in the forefront of astronomic research since their first discovery, at least 50 years ago . The putative supermassive black hole (SMBH) at their center characterizes their properties and regulates the evolution of these objects. I investigate the evolution of active galactic nuclei (AGN) in the context of a merger-driven evolution scheme. Under this assumption, galaxy mergers trigger activity in galaxies, both in the form of intense star-formation, as well as nuclear activity. This investigation uses the Caltech-Jodrell Bank flat-spectrum (CJF) sample, a statistically complete sample of compact, radio-loud AGN. I find evidence supporting the merger-driven evolution scheme of AGN, exhibiting the relevance of merger events in active galaxies. In particular, almost 30% of the CJF sources in the local Universe (z<0.4) show evidence of recent past, present, or possible future mergers. This is important in light of the unbiased selection effects of the CJF sample. In addition, I find a broken correlation between the near-infrared luminosity of the CJF sources and their total radio luminosity at 5 GHz. Low luminosity sources show an excess of near-infrared emission, compared to their high luminosity counterparts. A correlation between near-infrared colors and multiwavelength variability is also found. Finally, I trace the different stages of AGN evolution by selecting individual sources that fit the respective selection criteria, finding 14 promising candidates for binary black hole (BBH) systems in the CJF. One of the most prominent constituents of radio-loud active galaxies are their radio jets. The morphology, properties, and evolution of the CJF jet ridge lines are studied, in light of a recently revisited kinematic paradigm for BL Lac objects. Different measures for the width, the width evolution, the linear evolution, and the curvature of the jet ridge lines are developed and a statistical analysis of the whole sample on that basis is conducted. BL Lac objects are found to have substantially wider jets than quasars. They are also found to show larger changes in their widths, but significantly weaker linear evolution of their jet ridge lines. We find indications of active evolution of the jet length and linear evolution with time (as a function of redshift). An envelope is found confining a correlation between the total linear evolution of the CJF jet ridge lines and the radio luminosity of the corresponding sources. The above results are explained in terms of the combination of helical structure for AGN jets and projection effects. Coupled to the kinematics of the AGN jets is the emission of gamma-ray radiation. In light of the excellent quality of kinematic data available for the CJF, as well as the wealth of new gamma-ray information provided by the Fermi-LAT program, I investigate the gamma-ray properties of the CJF sample, in terms of their jet kinematics and properties. I find that gamma-ray detected sources show on average higher apparent velocities than their non-detected counterparts. I note however the existence of a low-velocity population of gamma-ray detected CJF sources, that put the argument of beaming as the source of gamma-ray photons under debate. I study a possible correlation between the gamma-ray detection of CJF sources, their luminosity, and their jet morphology. I find a correlation between the gamma-ray luminosity and the maximum apparent jet speed for the gamma-detected CJF sources. The correlation is stronger for variable sources and for those identified as BL Lacs. I find that gamma-detected sources show substantially wider jet ridge lines, with stronger evolution of their widths compared to non-detected sources. I find no significant difference between gamma-detected and non-detected sources concerning the linear evolution of their jet ridge lines. The absence of a strong correlation between gamma-ray properties of the CJF sources and their kinematics is interpreted in the context of a spine-sheath geometry of AGN jet, where, at the low observing frequency used for the CJF, only the slow outer sheath of the jet is uncovered. gamma-ray emission is assumed to originate in the ultra-relativistic spine of AGN jets

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