The tight correlations observed between galaxies and their SMBH provides compelling evidence that the evolution of the galaxy and its central black hole are strongly linked. This is generally attributed to feedback mechanisms which, according to simulations, often take the form of outflows of gas, quenching star formation in the host galaxy and halting accretion onto the central black hole. While there are a number of plausible ways that outflows could be produced, recent results have shown that in some cases radio jets could be responsible for driving fast outflows of gas. One such example is seen in the nearby radio galaxy 3C293. In this talk I will present results from JVLA radio observations where we detect fast outflows (~1200 km/s) of neutral gas which are being driven by the radio-jet approximately 0.5 kpc from the central core, providing direct evidence for jet-ISM interaction. This is accompanied with recent IFU observations showing that ionised gas outflows are also being driven by the radio jet. Pinpointing the location of these outflows enables us to derive crucial parameters, such as the mass outflow rates and kinetic energy involved, which we can compare to predictions from galaxy evolution simulations.

We previously reported discovering that blazars have distinctive infrared colors as seen in the WISE mission. Of particular note are γ-ray blazars, the locus of whose colors roughly overlaps with QSOs contours but which is more tightly delimited and bluer than ULIRGs and Seyferts. Since a large fraction of γ-ray sources are unassociated with any point source, but are expected to be blazars, identifying a WISE-candidate blazar in the γ-ray source field enables efficient followup studies. In an effort to better understand why blazars have these colors, we reduced and analyzed Spitzer Infrared Spectrometer (IRS) measurements on 73 blazars of varying types, some at several epochs. These spectra can be used to study the continuum emission (non-thermal), and search for atomic or other spectral features.

We present Faraday rotation measure (RM) properties of seven active galactic nuclei (AGN), observed with the NRAO VLA at three epochs in 2012-2014. Data was taken at 1.4, 2.2, 5.0, 8.2, 15.4, 22.4, 33.5 and 43.1 GHz quasi simultaneously in full polarization mode. For the first time RMs were calculated in a range of wavelengths covering more than one order of magnitude: from 21 cm up to 6 mm. We measured RM for each source and showed a tendency to increase its value toward high frequencies according to the law |RM|~νa with a = 1.6±0.1. For 0710+439, we observed an increase over the frequency range of 4 orders of magnitude and measured one of the highest RM ever, (−89±1)⋅103 rad/m2. Analysis of different epochs shows variations of the value and the sign of RM on short and long time-scales. This may be caused by changing physical conditions in the compact regions of the AGN jets, e.g., strength of magnetic field, particle density and so on.

We present the results of a theoretical study on the influence of dust particles on the polarization properties of the radiation that propagates along the jet in AGNs. First, a model for describing the interaction of dust particles, in addition to the electrons and ions, with electromagnetic radiation in a magneto-active plasma has been developed. From here, the contribution of dust particles to the Faraday rotation of the plane of polarization of the electric vector can be deduced. This model is evaluated for the outer region of the jet where the presence of dust particles are assumed, the magnetic field is weak and the electron density is low. Our results show that the dust particles give a significant contribution to the linear Faraday rotation measure.

We discuss the lack of a clear jet-break in the optical and X-ray afterglow light curve of GRB 130427A, which suggests that a very large isotropic energy is emitted in this burst.

The correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

In this work, we compiled 604 blazars with available core-dominance parameter, out of which 149 blazars are known to have γ-ray emissions. We compared the logR between the 149 Fermi-detected blazars (FDB) and the rest non-Fermi-detected blazars (non-FDB), and found that the average values are < logR > = 1.12 ± 0.88 for FDBs and < logR > = 0.05 ± 0.94 for non-FDBs. A K-S test shows that the probability for the distributions of FDB and non-FDB to come from the same parent distribution is P = 2.38 × 10−7. We also investigated the correlation between the core-dominance parameters and the γ-ray emission variability index (VI) for 125 FDBs (45 BLs and 79 FSRQs), and found that there is a tendency for VI to increase with the core-dominance parameter for 79 FSRQs, but there is no such tendency for 46 BLs.

Many theoretical models of Active Galactic Nuclei (AGN) predict that the X-ray corona, lying above the black hole, constitutes the base of the X-ray jet. Thus, by studying the exact geometry of the close black hole environment, we can pinpoint the launching site of the jet. Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lagging behind the corresponding hard band X-ray variations) can yield significant information about the geometrical properties of the AGN, such as the location of the X-ray source, as well as the physical properties of the the black hole, such as its mass and spin. In the frame-work of the lamp-post geometry, I present the first systematic X-ray time-lag modelling results of an ensemble of 12 AGN, using a fully general relativistic (GR) ray tracing approach for the estimation of the systems' response functions. By combing these state-of-the art GR response models with statistically innovative fitting routines, I derive the geometrical layout of the close BH environment for each source, unveiling the position of the AGN jet-base.

AGN reverberate when the broad emission lines respond to changes of the ionizing thermal continuum emission. Reverberation measurements have been commonly used to estimate the size of the broad-line region (BLR) and the mass of the central black hole. However, reverberation mapping studies have been mostly performed on radio-quiet sources where the contribution of the jet can be neglected. In radio-loud AGN, jets and outflows may affect substantially the relation observed between the ionizing continuum and the line emission. To investigate this relation, we have conducted a series of multi-wavelength studies of radio-loud AGN, combining optical spectral line monitoring with regular VLBI observations. Our results suggest that at least a fraction of the broad-line emitting material can be located in a sub-relativistic outflow ionized by non-thermal continuum emission generated in the jet at large distances (> 1 pc) from the central engine of AGN. This finding may have a strong impact on black hole mass estimates based on measured widths of the broad emission lines and on the gamma-ray emission mechanisms.

The jet phenomenon is a trademark of active galactic nuclei (AGN). In most general terms, the current understanding of this phenomenon explains the jet appearance by effects of relativistic plasma physics. The fundamental source of energy that feeds the plasma flow is believed to be the gravitational field of a central supermassive black hole. While the mechanism of energy transfer and a multitude of effects controlling the plasma flow are yet to be understood, major properties of jets are strikingly similar in a broad range of scales from stellar to galactic. They are supposed to be controlled by a limited number of physical parameters, such as the mass of a central black hole and its spin, magnetic field induction and accretion rate. In a very simplified sense, these parameters define the formation of a typical core–jet structure observed at radio wavelengths in the region of the innermost central tens of parsecs in AGN. These core–jet structures are studied in the radio domain by Very Long Baseline Interferometry (VLBI) with milli- and sub-milliarcsecond angular resolution. Such structures are detectable at a broad range of redshifts. If observed at a fixed wavelength, a typical core–jet AGN morphology would appear as having a steep-spectrum jet fading away with the increasing redshift while a flat-spectrum core becoming more dominant. If core–jet AGN constitute the same population of objects throughout the redshift space, the apparent “prominence” of jets at higher redshifts must decrease (Gurvits 1999): well pronounced jets at high z must appear less frequent than at low z.

We have undertaken a Spitzer campaign to measure the IR structures and spectra of low-redshift 3CRR radio galaxies. The results show that the 3.6 – 160 μm infrared properties vary systematically with integrated source power, and so demonstrate that contemporary core activity is characteristic of the behaviour of sources over their lifetimes. IR synchrotron emission is seen from jets and hotspots in some cases. Thermal emission is found from a jet/gas interaction in NGC7385. Most of the near-IR integrated colours of the low-redshift 3CRR radio galaxies are similar to those of passive galaxies, so that IR colours are poor indicators of radio activity.

Radio sources are divided into two distinct morphological groups of objects: Fanaroff-Riley type I and type II sources. There is a relatively sharp luminosity boundary between these at low frequency. The nature of the FR division is still an open issue, as are the details of the evolutionary process in which younger and smaller GHz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources become large-scale radio structures. It is still unclear whether FRII objects evolve to become FRIs, or whether a division has already occurred amongst CSS sources and some of these then become FRIs and some FRIIs. We explored evolution scenarios of AGNs using new radio, optical and X-ray data of unstudied so far Low Luminosity Compact (LLC) sources. We suggest that the determining factors of the further evolution of compact radio objects could occur at subgalactic (or even nuclear) scales, or they could be related to the radio jet - interstellar medium (ISM) interactions and evolution. Our studies show that the evolutionary track could be related to the interaction, strength of the radio source and excitation levels of the ionized gas instead of the radio morphology of the young radio source.

Accreting supermassive black holes and starburst regions influence their host galaxies through kinetic/radiative feedback processes. To better understand the gas evolution of a Seyfert galaxy, in this study we perform fully 3D hydrodynamical simulations with radiative cooling considering the presence of star formation regions, supernova feedback and small-scale (1 kpc) jet propagation in the central region of an active spiral galaxy. We compute the gas mass lost by the system and we conclude that a kpc-scale outflow is generally established only when a nuclear starburst region is coupled to a supermassive black hole jet.

The nearby radio galaxy M87 offers a unique opportunity for exploring the connection between γ-ray production and jet formation at an unprecedented linear resolution. However, the origin and location of the γ-rays in this source is still elusive. Based on previous radio/TeV correlation events, the unresolved jet base (radio core) and the peculiar knot HST-1 at >120 pc from the nucleus are proposed as candidate site(s) of γ-ray production. Here we report our intensive, high-resolution radio monitoring observations of the M87 jet with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from February 2011 to October 2012. During this period, an elevated level of the M87 flux is reported at TeV with VERITAS. We detected a remarkable flux increase in the radio core with VERA at 22/43 GHz coincident with the VHE activity. Meanwhile, HST-1 remained quiescent in terms of its flux density and structure at radio. These results strongly suggest that the TeV γ-ray activity in 2012 originates in the jet base within 0.03 pc (projected) from the central supermassive black hole.

Recent measurements of frequency-dependent shift of radio-core locations indicate that the ratio of the magnetic to kinetic energy flux (the σ parameter) is of the order of unity. These results are consistent with predictions of magnetically-arrested-disk (MAD) models of a jet formation, but contradict the predictions of leptonic models of γ-ray production in luminous blazars. We demonstrate this discrepancy by computing the γ-ray-to-synchrotron luminosity ratio (the q parameter) as a function of a distance from the black hole for different values of σ and using both spherical and planar models for broad-line region and dusty torus. We find that it is impossible to reproduce observed q ≫ 1 for jets with σ ≥ 1. This may indicate that blazar radiation is produced in reconnection layers or in spines of magnetically stratified jets.

Due to its high angular resolution, the Chandra Observatory has allowed the discovery and detailed study of extragalactic X-ray jets. Although supermassive black holes are regularly found in the cores of massive galaxies and X-ray emission is detected from ~80% of these, X-ray and radio jets are only detected in a small fraction of “normal” galaxies. X-ray jets are either single-sided or double-sided and, with only one possible exception, are found to have radio emission. However many radio jets are not detected in current X-ray observations. The expanding jets produce cavities in the surrounding hot gas in the galaxy halos. By determining how much gas has been pushed out of these cavities, we can determine the mechanical energy and power of the jet.

Bent-tailed (BT) radio sources have long been known to trace over densities in the Universe up to z ~ 1 and there is increasing evidence this association persists out to redshifts of 2. The morphology of the jets in BT galaxies is primarily a function of the environment that they have resided in and so BTs provide invaluable clues as to their local conditions. Thus, not only can samples of BT galaxies be used as signposts of large-scale structure, but are also valuable for obtaining a statistical measurement of properties of the intra-cluster medium including the presence of cluster accretion shocks & winds, and as historical anemometers, preserving the dynamical history of their surroundings in their jets. We discuss the use of BTs to unveil large-scale structure and provide an example in which a BT was used to unlock the dynamical history of its host cluster. In addition to their use as density and dynamical indicators, BTs are useful probes of the magnetic field on their environment on scales which are inaccessible to other methods. Here we discuss a novel way in which a particular sub-class of BTs, the so-called ‘corkscrew’ galaxies might further elucidate the coherence lengths of the magnetic fields in their vicinity. Given that BTs are estimated to make up a large population in next generation surveys we posit that the use of jets in this way could provide a unique source of environmental information for clusters and groups up to z = 2.

We have completed a Chandra snapshot survey of 54 radio jets that are extended on arcsec scales. These are associated with flat spectrum radio quasars spanning a redshift range z=0.3 to 2.1. X-ray emission is detected from the jet of approximately 60% of the sample objects. We assume minimum energy and apply conditions consistent with the original Felten-Morrison calculations in order to estimate the Lorentz factors and the apparent Doppler factors. This allows estimates of the enthalpy fluxes, which turn out to be comparable to the radiative luminosities.

We are undertaking a detailed investigation, based on the available evidence, of the sequence of events that led to the historical discovery of the first quasar, 3C273.

Feedback provided by relativistic jets may be effective in shaping the galaxy luminosity function. The quenching mode (quasar mode) at redshifts ~2-3 potentially disperses gas in star-forming galaxies. The maintenance mode (radio mode) heats the gas in galaxy clusters counteracting cooling flows. A number of authors have examined the effect of relativistic jets in dispersing clouds in the kpc-scale inhomogeneous interstellar medium of evolving galaxies. We have also investigated a particular case of maintenance-mode feedback in our simulation of the iconic radio galaxy / cooling flow cluster Hydra A. Modelling of the knots produced by the jets in the inner 10 kpc provides an estimate of 0.8 – 0.9 c for the velocities of the jets in agreement with other velocity estimates for FR1 jets. The addition of jet precession provides realistic simulations of the morphology of the Hydra A radio source and raises interesting questions as to the role of black hole and disk precession, in general, in galaxy formation.