We present a multi-wavelength study of the radio galaxy PKS J0334-3900, which resides at the centre of Abell 3135. Using Australia Telescope Compact Array (ATCA) observations at 1.4, 2.5, 4.6 & 8.6 GHz, we performed a detailed analysis of PKS J0334-3900. The morphology and spectral indices give physical parameters that constrain the dynamical history of the galaxy, which we use to produce a simulation of PKS J0334-3900. This simulation shows that the morphology can be generated by a wind in the intracluster medium (ICM), orbital motion caused by a companion galaxy, and precession of the black hole (BH).

Additionally, ATCA polarisation data was used to obtain rotation measure values along the line of sight to PKS J0334-3900. Using our simulation we are able to infer the distance between the jets along the line of sight to be 154 ± 16 kpc, which when combined with the difference in rotation measure between the jets provides a novel new way to estimate the average magnetic field within the cluster. A lower limit to the cluster magnetic field was calculated to be 0.09±0.03 μG. We have shown that different techniques can be applied to observations of jets in galaxies to infer information on cluster environments.

Bent-double sources, sometimes referred to as wide- or narrow-angle tails, are most likely the result of ram pressure from either the motion of the source through a dense medium or the "cluster weather." These unusual sources have long been associated with high density, high velocity dispersion, and turbulent environments of massive clusters, however a surprising number have been found in lower mass systems. We focus our attention on a sample of such sources in galaxy groups where the velocity dispersion is significantly lower. We have acquired multi-frequency radio continuum observations using the GMRT of our bent-double sample and new optical spectroscopy to measure the velocity dispersion of groups hosting these bent-double sources. Our goal is to derive an estimate of the density of the intergalactic medium in these groups. Here, we present GMRT data for one source in our sample.

We present a uniform analysis of Chandra archival observations of a complete sample of ~ 200 3C sources at z < 0.5. We measured the X-ray intensity of the nuclei and of any radio hot spots and jet features with associated X-ray emission. X-ray fluxes in three energy bands, i.e., soft, medium, and hard, for all the sources analyzed are also reported. For the stronger nuclei, we also applied the standard spectral analysis, which provides the best-fit values of the X-ray spectral index and absorbing column density. In addition, a detailed analysis of bright X-ray nuclei that could be affected by pile-up has been performed. X-ray emission was detected for all the nuclei of the radio sources in our sample.

Supermassive black holes (SMBHs) play key roles in galaxy and cluster evolution. This is most clearly seen in the “fossil record” that is imprinted in the gas rich atmospheres of early type galaxies, groups, and clusters by powerful SMBH outbursts. From a detailed X-ray study of M87, we present the properties of a typical SMBH outburst, its evolution, and the energy partition between shocks and the enthalpy of the gas cavities inflated by the SMBH. About 12 Myr ago, the SMBH in M87 inflated a cavity of relativistic plasma which is still centered near the galaxy nucleus. This outburst drove a shock into the surrounding gas. For M87, we show that the outburst duration is a few Myr and that about 50% of the total energy (5 × 1057 ergs) resides in the bubble inflated by the jet from the SMBH, that 25% of the outburst energy is deposited directly into the ambient atmosphere by the shock, and that 25% of the outburst energy is lost from the radiatively bright core as the weak shock moves to large radii. We conclude by describing a future X-ray mission, SMART-X, with < 1” angular resolution that would allow us to study the evolution of SMBHs and the hot, X-ray emitting atmospheres from high redshifts to the present for M87-like systems.

We are conducting a large survey of distant clusters of galaxies using radio sources with bent jets and lobes as tracers. These radio sources are driven by AGN and achieve their bent morphologies through interaction with the surrounding gas found in clusters of galaxies. Based on low-redshift studies, these types of sources can be used to identify clusters very efficiently. We present initial results from our survey of 653 bent-double radio sources with optical hosts too faint to appear in the SDSS. The sample was observed in the infrared with Spitzer, and it has revealed ~200 distant clusters or proto-clusters in the redshift range z ~ 0.7 - 3.0. The sample of bent-doubles contains both quasars and radio galaxies enabling us to study both radiative and kinetic mode feedback in cluster and group environments at a wide range of redshifts.

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.

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 explore the connection between the black hole mass and its relativistic jet for a sample of radio-loud AGN (z < 1), in which the relativistic jet parameters are well estimated by means of long term monitoring with the 14m Metsähovi millimeter wave telescope and the Very Long Base-line Array (VLBA). NIR host galaxy images taken with the NOTCam on the Nordic Optical Telescope (NOT) and retrieved from the 2MASS all-sky survey allowed us to perform a detailed surface brightness decomposition of the host galaxies in our sample and to estimate reliable black hole masses via their bulge luminosities. We present early results on the correlations between black hole mass and the relativistic jet parameters. Our preliminary results suggest that the more massive the black hole is, the faster and the more luminous jet it produces.

AGN jets are detected via their radio and/or gamma-ray emissions while the accretion disks are detected by their optical and UV radiation. Observations of the radio and optical luminosities show a strong correlation between the two luminosities. However, part of this correlation is due to the redshift or distances of the sources that enter in calculating the luminosities from the observed fluxes and part of it could be due to the differences in the cosmological evolution of luminosities. Thus, the determination of the intrinsic correlations between the luminosities is not straightforward. It is affected by the observational selection effects and other factors that truncate the data, sometimes in a complex manner [Antonucci (2011) and Pavildou et al. (2010)]. In this paper we describe methods that allow us to determine the evolution of the radio and optical luminosities, and determine the true intrinsic correlation between the two luminosities. We find a much weaker correlation than observed and sub-linear relations between the luminosities. This has a significant implication for the jet and accretion disk physics.

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.

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.

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.

The discovery of relativistic jets and superluminal sources associated with accreting X-ray binaries in the Galaxy opened new ways of investigating the physics of outflows from compact objects. The short timescales and relatively large angular sizes of Galactic jets allow to probe the physics of relativistic outflows to unprecedented details. In this article I discuss results of recent modelling of Galactic jets, covering both radiative and dynamical aspects, which can shed light on different features of their extragalactic cousins.

Theoretical and observational work show that jets from AGN can trigger star formation. However, in the Milky Way the first -and so far- only clear case of relativistic jets inducing star formation has been found in the surroundings of the microquasar GRS 1915+105. Here we summarize the multiwavelength observations of two compact star formation IRAS sources axisymmetrically located and aligned with the position angle of the sub-arcsec relativistic jets from the stellar black hole binary GRS 1915+105 (Mirabel & Rodríguez 1994). The observations of these two star forming regions at centimeter (Mirabel & Rodríguez 1998), millimeter and infrared (Chaty et al. 2001) wavelengths had suggested -despite the large uncertainties in the distances a decade ago- that the jets from GRS 1915+105 are triggering along the radio jet axis the formation of massive stars in a radio lobe of bow shock structure. Recently, Reid et al. (2014) found that the jet source and the IRAS sources are at the same distance, enhancing the evidence for the physical association between the jets from GRS 1915+105 and star formation in the IRAS sources. We conclude that as jets from AGN, jets from microquasars can trigger the formation of massive stars, but at distances of a few tens of parsecs. Although star formation induced by microquasar jets may not be statistically significant in the Milky Way, jets from stellar black holes may have been important to trigger star formation during the re-ionization epoch of the universe (Mirabel et al. 2011). Because of the relative proximity of GRS 1915+105 and the associated star forming regions, they may serve as a nearby laboratory to gain insight into the physics of jet-trigger star formation elsewhere in the universe.

The supermassive black hole in the center of the Milky Way, Sgr A*, displays a nearly flat radio spectrum which is typical for jets in Active Galactic Nuclei. Indeed, time dependent, magnetized models of radiatively inefficient accretion flows, which are commonly used to explain the millimeter, near-infrared, and X-ray emission of Sgr A* also often produce jet-like outflows. However, the emission from these models so far has failed to reproduce the flat radio spectrum. We show that current GRMHD simulations can naturally reproduce the flat spectrum, when using a two-temperature plasma in the disk and a constant electron temperature plasma in the jet. This assumption is consistent with current state-of-the art simulations, in which the electron temperature evolution is not explicitly modeled. Stronger magnetization and stronger shearing seen in the jet sheath could possibly explain the difference in electron heating between jet and disk. The model images and spectra are consistent with the radio sizes and spectrum of Sgr A*.

High frequency quasi-periodic oscillations (HF QPOs) are observed in the X-ray power-density spectra (PDS) of several microquasars and low mass X-ray binaries. Many proposed QPO models are based on oscillations of accretion toroidal fluid structures orbiting in the vicinity of a compact object. We study oscillating accretion tori orbiting in the vicinity of a Kerr black hole. We demonstrate that significant variation of the observed flux can be caused by the combination of radial and vertical oscillation modes of a slender, polytropic, perfect fluid, non-self-graviting torus with constant specific angular momentum. We investigate two combinations of the oscillating modes corresponding to the direct resonance QPO model and the modified relativistic precession QPO model.

We present an inhomogeneous synchrotron self-Compton (SSC) model for active parts of jets in low mass microquasars. We compare results of our model computed, for typical parameters of microquasars, with the sensitivity of Fermi-LAT.

A jet model represents well different X-ray states of the bright ULX IC342 X-1.

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 spiral galaxy M81 has a low-luminosity Active Galactic Nucleus in its center with a core and a one-sided curved jet, dubbed M81*, that is barely resolved with VLBI. To derive basic parameters such as the length of the jet, its orientation and curvature, the usual method of model-fitting with point sources and elliptical Gaussians may not always be the most appropriate one. We are developing Fourier-plane models for such sources, in particular an asymmetric triangle model to fit the extensive set of VLBI data of M81* in the u-v plane. This method may have an advantage over conventional ones in extracting information close to the resolution limit to provide us with a more comprehensive picture of the structure and evolution of the jet. We report on preliminary results.