Radio-loud Active Galactic Nuclei (AGN) produce relativistic jets that can be modelled with relativistic hydrodynamic (RHD) simulations. In this study we present two such simulations of jets, used to investigate the parameters required to reproduce structures consistent with both FR I and FRII jets. In the first simulation a Lorentz factor of 10 and supersonic flow of Mach 30 were chosen, while for the second simulation a Lorentz factor of 1.0014 with a supersonic flow of Mach 4 was used. Over similar distances scales the first case shows a well collimated beam with a strong shock at the interface between the jet and ambient medium while the second case shows a less stable beam and a larger cocoon. To determine whether the simulated physical structures are consistent with the observed FR I/II jets, the synchrotron emission has been calculated to produce radio maps at a single frequency of 1.5 GHz.

Observations of low luminosity active galactic nuclei (LLAGNs) and the hard state of black hole X-ray binaries (BHBs) show that the wind exists. Black hole in LLAGNs and hard state of BHBs accretes gas in hot accretion mode. In this paper, we first use magnetohydrodynamic (MHD) simulations of hot accretion flow around a black hole to study the origin of the wind. We find that the wind is driven by the combination of gradients of gas and magnetic pressure and centrifugal forces. Second, we use simulations with focus on the region around Bondi radius to study whether the wind can be generated outside Bondi radius. In the simulation studying hot accretion flow around Bondi radius, in addition to the black hole gravity, we also take into account the gravity of nuclei stars. We find that the wind can not be generated outside Bondi radius. The absence of the wind is due to the change of gravity potential.

We analyze the hard X-ray properties of five radio-loud active galactic nuclei with peculiar spectral shape. High-energy exponential cut-offs (HEC) in their hard X-ray 3-500 keV spectra are too high for radio loud AGNs (above 100 keV) or even absent.The probable reason of such visible spectral “peculiarity” can be due to the “jet contamination”, i.e we see some mixture of the jet and nuclear emission, but not pure emission of the innermost nucleus. Here we try to estimate the jet and nuclear components of the spectra for a sample of “peculiar” RL AGNs to find out whether these are real or fake features.

Following the discovery of the expansion of a young radio lobe associated with the bright radio source 3C 84 in the Seyfert galaxy NGC 1275 using VSOP monitoring observation with duration of 3 years, we further investigated its evolution by utilizing VLBA monitoring data taken by MOJAVE project. As the results, we confirmed the expanding motion of both the southern and northern lobes, and detected side-way expanding motions for the first time. In meantime, the total flux density of the lobes are decreasing, while total flux density associated with the nuclei is significantly increasing. This cooling of the radio lobe can be well-explained with the energy loss through the adiabatic cooling.

We present the analysis of the 93 ksec Chandra ACIS–S data for the galaxy CGCG 292–057 (z = 0.054), with complex radio structure indicative of the intermittent jet activity. In order to characterize precisely the spectrum of the unresolved low-luminosity active nucleus in the source, we performed detailed MARX/PSF simulations and studied the radial profile of the source region surface brightness. In this way, we have detected an additional X-ray component extending from a few up to ∼10 kpc from the unresolved core, which could be associated with the hot gaseous medium compressed and heated (up to 0.9 keV) by the expanding inner lobes of the radio galaxy. We modeled the X-ray spectrum of the unresolved nucleus assuming various emission models, including an absorbed power-law, a power-law plus thermal emission component, and a two-temperature thermal plasma. The best fit was however obtained assuming a power-law emission scattered by a hot ionized gas, giving rise to the 6.7 keV iron line.

Here we present some preliminary results of our analysis of the combined Chandra observations of the Pictor A radio galaxy. All the available Chandra data for the target, consisting of multiple pointings spanning over 15 years and amounting to the total exposure time of 464 ks, have been included in the analysis. We studied in detail the PSFs of the core region in the individual pointings, as well as the radial profile of the X-ray surface brightness of the source in the combined dataset, in order to discriminate between the radiative output of the unresolved core and the host galaxy. Based on these, we have performed spectral modeling of the active nucleus, constraining its variability.

By performing the multi-epoch monitoring observation with KaVA at 43 GHz, we investigate the kinematics of the notable newborn bright component C3 located at the tip of the recurrent jet of 3C 84. During 2015 August-September,we discover the positional flip of the C3 component about 0.4 milli-arcsecond in angular scale. The flux density of the C3 component coherently showed the monotonic increase after the flip during our monitoring period. These phenomena are in good agreement with characteristic behaviors of a jet propagation in clumpy ambient medium predicted in hydrodynamical simulations.

Large-scale, broad outflows are common in active galaxies. In systems where star formation coexists with an AGN, it is unclear yet the role that both play on driving the outflows. In this work we present three-dimensional radiative-cooling MHD simulations of the formation of these outflows, considering the feedback from both the AGN and supernovae-driven winds. We find that a large-opening-angle AGN wind develops fountain structures that make the expanding gas to fallback. Furthermore, it exhausts the gas near the nuclear region, extinguishing star formation and accretion within a few 100.000 yr, which establishes the duty cycle of these outflows. The AGN wind accounts for the highest speed features in the outflow with velocities around 10.000 km s−1 (as observed in UFOs), but these are not as cold and dense as required by observations of molecular outflows. The SNe-driven wind is the main responsible for the observed mass-loading of the outflows.

The Medicina and Noto radiotelescopes have been employed for over 14 years to monitor the flux density variations of a vast sample of blazars at different radio frequencies. Radio data are essential components of blazar spectral energy distribution (SED, spanning from radio waves to gamma rays), whose trend with luminosity and shape changes provide decisive information on the physics of extra-galactic jets and, eventually, on the mechanism extracting energy from the central black hole in radio-loud AGN. Observations presently carried out at 5, 8 and 24 GHz have taken advantage of the continually evolving control system installed at the antennas. A new, batch-wise analysis tool was also produced, in order to easily handle and reduce the datasets acquired in monthly sessions. We here describe the latest developments and achievements.

An understanding of the mechanisms that regulate the Active Galactic Nuclei passes through the study of their early life stages, observable in Compact Symmetric Objects. To this purpose, a study was carried out on two compact radio sources, based on data from the VLBA archive at different times and frequencies. The results are compatible with an intermediate scenario between the two main theories about these objects: frustration and youth.

We have conducted VLBI monitoring observations for a radio galaxy 3C 84 to investigate how the pc scale jet structure changes over a long period. VERA, a VLBI observation network in Japan, was used for the observation. The C3 component of the jet has continuously moved toward the south from the core. The motion was, however, not straight, but it showed a bending of about 0.3 mas (0.1 pc) with a time scale of 500-1000 days. Two models explaining the bending, local brightness distribution change or real change of the jet traveling direction, are discussed.

The hot ISM in early-type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra observations point to key evolutionary mechanisms, (e.g., kim12). In our Chandra Galaxy Atlas (CGA) project, taking full advantage of the Chandra capabilities, we systematically analyzed the archival Chandra data of 72 ETGs and produced uniform data products of the hot gas properties. The main data products include spatially resolved 2D spectral maps of the hot gas from individual galaxies. We emphasize that new features can be identified in the spectral maps which are not easily visible in the surface brightness maps. The high-level images can be viewed at the dedicated CGA website, and the CGA data products can be downloaded to compare with other wavelength data and to perform user-specific analyses. Utilizing our data products, we will further address focused science topics.

By constructing images of the Faraday rotation measure (RM) of large scale astrophysical jets, the line-of-sight magnetic field component and electron density in the region of Farady rotation can be investigated. A significant gradient in the RM transverse to the jet direction may indicate a corresponding gradient in the line-of-sight magnetic field, implying a toroidal or helical magnetic field, which would, in turn, imply the presence of an associated electrical current in the jet. The detection of such large scale gradients can reliably demonstrate that helical or toroidal fields can persist to large distances from the central AGN. We present a kiloparsec-scale Faraday rotation map of NGC 6251 that shows statistically significant transverse RM gradients across its kiloparsec scale jet structure that imply an outward current.

We propose that two emission regions are present in the decelerating jet of radio galaxy at this same moment. Isotropic electrons, in the farther blob as counted along the jet, up-scatter mono-directional soft radiation, from the closer blob, at a relatively large angles to the jet axis. Such model can naturally explain the large angle gamma-ray emission observed from radio galaxies.

It has been controversial for years that the accretion mode is different for bright active galactic nuclei (AGNs) and low-luminosity AGNs (LLAGNs). In this work, we compile from literature a sample of 32 LLAGNs, consisting 18 LINERs and 14 low Eddington ratio (λ) Seyfert galaxies. A strong negative correlation between the radio loudness RUV and the optical to X-ray spectral index αox is reported for the first time. We further demonstrate that this negative correlation can be understood consistently and comprehensively under the truncated accretion — jet model, a model that has been applied successfully to LLAGNs. We argue that the scatter in the observations is mainly due to the spread in the viscosity parameter α of a hot accretion flow, a parameter that can potentially serve as a diagnosis of the strength and/or configuration of magnetic fields in accretion flows.

We re-analyzed OJ287 in 120 Very Long Baseline Array (VLBA, MOJAVE) observations (at 15 GHz) covering the time span between Apr. 1995 and Apr. 2017. We find that the radio jet motion over the sky is consistent with a precessing and nutating jet source. The variability of the radio flux-density can be explained by Doppler beaming due to a change in the viewing angle. We suggest that part of the optical emission is due to synchrotron emission related to the jet radiation. We find a strikingly similar scaling for the timescales for precession and nutation as indicated for SS433 with a factor of roughly 50 times longer in OJ287.

We constrained the jet proper motion of PMN J2134–0419 at z = 4.33 to μ = 0.035±0.023mas yr−1 using very long baseline interferometry (VLBI). This is the second most distant source where such a measurement could be made. Another distant blazar SDSS J1026+2542 (z = 5.27) shows jet component proper motions up to μ = 0.112 ± 0.031 mas yr−1. In both cases, the measured values are consistent with the expectations of current ΛCDM cosmological models.

Black holes at the centers of the galaxies grow mainly by the processes of accretion, mergers, and consumption of stars. In the case of gas accretion with cooling sources, the flow is momentum driven, after which the black hole reaches a saturated mass, and subsequently, it grows only by consumption of stars. In addition, we include the effect of mergers on the growth of black hole spin and mass and study its evolution as a function of redshift in a ΛCDM cosmology using an initial seed mass and spin distribution functions that we have derived. For the stellar ingestion, we have assumed a power-law density profile for the galaxy in our framework of a new relativistic loss cone theory that includes the effect of the black hole spin. We predict the impact of the evolution on the M•−σ relation and compare it with available observations.

Supernovae and astrophysical jets are two of the most energetic and intriguing objects in the universe. We examine an interesting scenario that involves the interaction of these two extreme phenomena, motivated by observations of the W50-SS433 system: a jet launched from the microquasar SS433 (an X-ray binary) located inside a supernova remnant, W50. These observations revealed a unique morphology of the remnant, attributed to the presence of the jet. We performed full 3D relativistic hydrodynamic simulations to better capture the interaction between the remnant and the jet and post-processed the data with a radiative transfer code to create emission maps.

The occurence rate of tidal disruption events (TDEs) by survey missions depend on the black hole mass function of the galaxies, properties of the stellar cusp and mass of the central black hole. Using a power law density profile with Kroupa mass function, we solve the steady state Fokker-Planck to calculate the theoretical capture rate of stars by the black hole. Using a steady accretion model, the Schechter black hole mass function (BHMF) and the cosmological parameters, we calculate the detection rate of TDEs for various surveys which is then fit with the observed TDE rates to extract the Schechter parameters. The rate tension between observation (∼10−5yr−1) and theory (∼10−4yr−1 for individual galaxies is explained by the statistical average over the BHMF.