Neutral hydrogen (HI) 21 cm absorption has been detected against more and more powerful radio jets. In this work, based on the Guppta et al. 2006a sample, we present our preliminary study of the correlations between the HI column density N(HI) and the jet power, N(HI) versus the low frequency luminosity at 408MHz, and N(HI) versus the radio luminosity at 1400MHz.
Using our theory for the production of relativistic outflows, we estimate the jet launching radius and the inferred mass accretion rate for 52 low-power radio-loud AGNs based on the observed jet powers. Our analysis indicates that (1) a significant fraction of the accreted energy is required to convert the accreted mass to relativistic energy particles for the production of the jets near the event horizon, (2) the jets launching radius moves radially toward the horizon as the mass accretion rate or jets power increases, and (3) no jet/outflow formation is possible beyond 44 gravitational radii…
Relativistic jets are collimated plasma outflows with relativistic speeds. Astrophysical objects involving relativistic jets are a system comprising a compact object such as a black hole, surrounded by rotating accretion flows, with the relativistic jets produced near the central compact object. The most accepted models explaining the origin of relativistic jets involve magnetohydrodynamic (MHD) processes. Over the past few decades, many general relativistic MHD (GRMHD) codes have been developed and applied to model relativistic jet formation in various conditions. This short review provides a…
We address the very large diversity of the jet production efficiency in active galactic nuclei (AGNs) by using data on low redshift AGNs selected from the Swift/BAT catalog and having black hole (BH) masses larger than $10^{8.5}\,M_{\odot}$. Most of these AGNs accrete at intermediate rates and have bolometric luminosities dominated by mid-IR radiation. Our sample contains $14\%$ radio-loud (RL), $6\%$ radio-intermediate (RI), and $80\%$ radio-quiet (RQ) AGNs. All RL objects are found to have extended radio structures and most of them have classical FR II morphology. Converting their radio loud…
Jet Power, Bulk Lorentz Factor, Black Hole Spin, and Magnetic Field of Accretion Disk in Jetted Active Galactic Nuclei: A Large Gamma-Ray Emission Sample
Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）；Center for Astrophysics, Guangzhou University（广州大学天体物理中心）；Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province（广东省教育厅天文学科学与技术研究实验室）；Center for Astronomy and Astrophysics and Department of Physics, Fudan University（复旦大学天文与天体物理中心及物理系）；Department of Astronomy, University of Science and Technology of China（中国科学技术大学天文系）；School of Astronomy and Space Science, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Shanghai Astronomical Obs（上海天文台）
KaVA (KVN and VERA Array) is a new combined VLBI array with KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). First, we briefly review the imaging capabilities of KaVA array which actually achieves more than three times better dynamic range than that achieved by VERA alone. The KaVA images clearly show detailed structures of extended radio jets in AGNs. Next, we represent the key science program to be led by KaVA AGN sub working group. We will conduct the monitoring observations of Sgr A* and M87 because of the largeness of their central super-massive black hole angula…
Radio-Loud (RL) Active Galactic Nuclei (AGNs) are among the brightest astrophysical sources at all wavelengths. Their relativistic jets can affect both their Supermassive Black Holes (SMBHs) growth and the surrounding intergalactic medium. While in the radio band these jets can be observed at all scales (from pc to Mpc scales), their X-ray and γ-ray emission is expected to be concentrated on very small scales (<10 pc). However, after the launch of the Chandra X-ray telescope, several kpc-scale jets were detected and the mechanism responsible for their high-energy radiation at these scales is s…
We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolutions of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the m…
Relativistic jets are observed only in the low/hard and intermediate states of X-ray binaries (XRBs), and are switched off in the thermal state, but they appear to be present in both low-luminosity and luminous active galactic nuclei (AGNs). It is widely believed that strong large-scale magnetic fields is a crucial ingredient in jet production; such fields can be attained only through efficient advection from the outer disc. We suggest that geometrically thin accretion discs with magnetic outflows are present in luminous radio-loud AGNs; this is likely because the interstellar medium provides …
In the study of radiation mechanisms of AGNs' jets, hadronuclear (pp) interactions are commonly neglected, because the number density of cold protons in the jet is considered insufficient. Very recently, our previous work proves that pp interactions in the low TeV luminosity AGNs, which have potential to generate detectable very-high-energy (VHE) emission, could be important. Based on this, the one-zone pp model is employed to study low-state quasi-simultaneous spectral energy distributions of a sample of low TeV luminosity AGNs in this work. Our modeling results show that the gamma-ray genera…
We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm VLBA surveys, spanning observations between 1994 Aug 31 and 2013 Aug 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-r…
Suzaku View of the Swift/BAT Active Galactic Nuclei. V. Torus Structure of Two Luminous Radio-loud AGNs (3C 206 and PKS 0707-35)
We present the results from broad-band X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei with hard X-ray luminosities of 10^{45.5} erg s^{-1} and 10^{44.9} erg s^{-1} (14--195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (~ 60% in the 14--195 keV band) contribution from the jet, while it is negligible in PKS 0707-35. We can successfully model the spectra with the jet component (for 3C 206), the transmitted …
Compact steep-spectrum sources (CSSs) likely represent a population of young radio-loud active galactic nuclei (AGNs) and have been identified as gamma-ray emitting sources. We present a comprehensive analysis of their gamma-ray emission observed with Fermi/LAT and establish their broadband spectral energy distributions (SEDs). We derive their jet properties by the SED fits with a two-zone leptonic model for radiations from the compact core and large-scale extended region, and explore the possible signature of a unification picture of jet radiation among subclasses of AGNs. We show that the ob…
Relativistic jets of plasma are a key ingredient of many types of Active Galactic Nuclei (AGN). Today we know that AGNs are powered by the accretion of inter stellar material into the gravitational field of a Super Massive Black Hole and that this process can release as much power as a whole galaxy, like the Milky Way, from a region that is comparable to the Solar System in size. Depending on the properties of the central energy source, a large fraction of this power can be involved in the acceleration of magnetized plasmas at relativistic speeds, to form large scale jets. The presence of jets…
The correlation between the jet power and accretion disk luminosity is investigated and analyzed with our model for 7 samples of low luminosity active galactic nuclei (LLAGNs). The main results are: (1) the power-law correlation index ($P_{jet} \propto L_{disk}^μ$) typically ranges $μ=0.4-0.7$ for the LLAGN samples, and there is a hint of steep index for the LLAGN sample which hosted by a high fraction of elliptical galaxies, and there are no significant correlation between the $μ$ and the LLAGN types (Seyfert, LINER); (2) for $μ\approx$1, as noted in Liu et al., the accretion disk dominates t…
The very existence of more than a dozen of high-redshift (z>4) blazars indicates that a much larger population of misaligned powerful jetted AGN was already in place when the Universe was <1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High redshift blazars themselves seem to be failing in producing extended radio-lobes, raising questions about the connection between such class and the vaster population of radio-galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) rad…
We restudy the issue of cross-correlations between broad-line and jet emission variations, and aim to locate the position of radio (and gamma-ray) emitting region in jet of active galactic nuclei (AGNs). Considering the radial profiles of the radius and number density of clouds in a spherical broad-line region (BLR), we derive new formulae connecting jet emitting position $R_{\rm{jet}}$ to time lag $τ_{\rm{ob}}$ between broad-line and jet emission variations, and BLR radius. Also, formulae are derived for a disk-like BLR and a spherical shell BLR. The model-independent FR/RSS method is used to…
Changing-look active galactic nuclei (CLAGNs) show the disappearance and reappearance of broad emission lines in a few years, which challenges the orientation-based AGN unification model. We reduce the X-ray data for five well-studied CLAGNs that show a strong change in broad emission lines in the past several decades. We find that the X-ray photon index, $Γ$, and the Eddington-scaled X-ray luminosity, $L_{\rm 2-10 keV}/L_{\rm Edd}$, normally follow negative and positive correlations when the Eddington ratio is lower and higher than a critical value of $\sim 10^{-3}$. We find that the CLAGNs o…
Dwarf galaxies are characterised by a very low luminosity and low mass. Because of significant accretion and ejection activity of massive black holes, some dwarf galaxies also host low-luminosity active galactic nuclei (AGNs). In a few dwarf AGNs, very long baseline interferometry (VLBI) observations have found faint non-thermal radio emission. SDSS J090613.77+561015.2 is a dwarf AGN owning an intermediate-mass black hole (IMBH) with a mass of $M_{BH} = 3.6^{+5.9}_{-2.3} \times 10^5 M_{sun}$ and showing a rarely-seen two-component radio structure in its radio nucleus. To further probe their na…
We present 15 GHz stacked VLBA images of 373 jets associated with active galactic nuclei (AGN) having at least five observing epochs within a 20 yr time interval 1994-2015 from the MOJAVE programme and/or its precursor, the 2 cm VLBA Survey. These data are supplemented by 1.4 GHz single-epoch VLBA observations of 135 MOJAVE AGNs to probe larger scale jet structures. The typical jet geometry is found to be close to conical on scales from hundreds to thousands of parsecs, while a number of galaxies show quasi-parabolic streamlines on smaller scales. A true jet geometry in a considerable fraction…
Fast magnetic reconnection events can be a very powerful mechanism operating in the core region of microquasars and AGNs. In earlier work, it has been suggested that the power released by fast reconnection events between the magnetic field lines lifting from the inner accretion disk region and the lines anchored into the central black hole could accelerate relativistic particles and produce the observed radio emission from microquasars and low luminosity AGNs (LLAGNs). Moreover, it has been proposed that the observed correlation between the radio emission and the mass of these sources, spannin…
In an effort to understand the cause of the apparent depletion in the number density of radio-loud AGNs at $z>3$, this work investigates the viability of the so-called Cosmic Microwave Background (CMB) quenching mechanism of intrinsically jetted, high-z AGNs, whereby Inverse Compton scattering of CMB photons off electrons within the extended lobes results in a substantial dimming of the lobe synchrotron emission at GHz frequencies, while simultaneously boosting their diffuse X-ray signal. We focus on five $z>3.5$ radio galaxies that have sufficiently deep Chandra exposure (> 50 ks) to warrant …
We use the results of relativistic hydrodynamic simulations of jet-ISM interactions in a galaxy with a radio-loud AGN to quantify the extent of ionization in the central few kpcs of the gaseous galactic disc. We perform post-process radiative transfer of AGN radiation through the simulated gaseous jet-perturbed disc to estimate the extent of photo-ionization by the AGN with an incident luminosity of $10^{45}~\mathrm{erg\,s^{-1}}$. We also map the gas that is collisionally ionized due to shocks driven by the jet. The analysis was carried out for simulations with similar jet power ($10^{45}~\mat…
Chandra Discovery of 10 New X-Ray Jets Associated With FR II Radio Core-Selected AGNs in the MOJAVE Sample
Chandra X射线观测站是研究活动星系核（AGN）喷流高能辐射过程的重要工具，我们从射电通量限制的MOJAVE（Monitoring of Jets in AGN with VLBA Experiments）高度相对论性喷流样本中选取了27个AGN样本，在千秒尺度上寻找X射线与射电辐射之间的相关性。该样本由所有MOJAVE类星体组成，这些类星体在1.4 GHz处具有超过100 mJy的扩展无线电发射和至少3”大小的无线电结构。钱德拉以前的观测已经揭示了样品中14个成员中的11个中的X射线射流，我们对其余13个源进行了新的观测。在后者中，10个有X射线喷射，使总体检测率达到约78%。我们的选择标准，这是基于高度紧凑，相对论束喷流发射和大的扩展无线电流量，从而提供了一个有效的方法来发现新的X射线喷流与活动星系核。探测到的X射线喷流形态一般与无线电发射有很好的相关性，除了那些在无线电波段显示出急剧弯曲的喷流。这些强大的FR II（Fanaroff-Riley II型）喷流的X射线发射机制可以解释为相对论喷流中的电子对宇宙微波背景（IC/CMB）光子的逆康普顿散射。我们推导出的喷气机的视角，假设一个非弯曲，非减速模型，通过使用超光速秒差距尺度的速度以及参数来自逆康普顿X射线模型。我们使用这些角度来计算最适合的多普勒和体积洛伦兹因子的射流，以及它们的可能范围，这导致在某些情况下的体积洛伦…
We construct samples of jetted active galactic nuclei (AGNs) with low-frequency radio data from the recent released TGSS AD1 catalog at 150 MHz. With these samples, we compare the properties of jet power for blazars, radio-loud narrow-line Seyfert 1 galaxies (RL-NLS1s), young radio sources (YRSs) and radio galaxies. The jet-disk connection, and the unification of jetted AGNs are explored. On the Eddington ratio --- Eddington-scaled jet power plane, jetted AGNs can be generally divided into two populations. Low power radio galaxies, low excitation FR IIs (LEG/FR IIs), and most YRSs show larger …
In the current paradigm, it is believed that the compact VLBI radio core of radio-loud AGNs represents the innermost upstream regions of relativistic outflows. These regions of AGN jets have generally been modeled by a conical outflow with roughly constant opening angle and flow speed. Nonetheless, some works suggest that a parabolic geometry would be more appropriate to fit the high energy spectral energy distribution properties and it has been recently found that, at least in some nearby radio-galaxies, the geometry of the innermost regions of the jet is parabolic. We compile here multi-freq…
Aims. Active galactic nuclei (AGNs) with EUV deficit are suggested to be powered by a MAD surrounding the black hole, where the slope of EUV spectra ($α_{\rm EUV}$) is found to possess a well positive relationship with the jet efficiency. In this work, we investigate the properties of X-ray emission in AGNs with EUV deficit for the first time. Methods. We construct a sample of 15 objects with EUV deficit to analyse their X-ray emission. The X-ray luminosity in 13 objects are newly processed by ourself, while the other 2 sources are gathered from archival data. Results. It is found that the ave…
Soft X-ray emission (0.5--2.0 keV) plays a pivotal role in regulating the optical and UV emission in the AGNs. We collected a sample of 1811 AGNs from the SDSS database and obtained various parameters of Balmer lines, optical continuum, MgII line \& UV continuum and studied their dependencies on soft X-ray luminosity. Based on the linear regression analysis, we found that FWHM$_{\text{MgII}}$ $\propto$ FWHM$_{\text{H}β}^{0.554}$ suggesting that UV emission is arising from a region relatively outside the broad line region (BLR) associated to the H$β$ emission and found a strong correlation betw…
In this work, we investigated the X-ray emission for a sample of young radio AGNs by combining their data from Chandra/XMM-Newton and at other wavebands. We find strong correlations between the X-ray luminosity $L_{\rm X}$ in 2$-$10 keV and the radio luminosities $L_{\rm R}$ at 5 GHz for VLBI radio-core, VLA radio-core and FIRST component, indicating that both pc- and kpc-scale radio emission strongly correlate with X-ray emission in these sources. We find approximately linear dependence of radio on X-ray luminosity in the sources with radiative efficient accretion flows (i.e., the Eddington r…
Based on broadband spectral energy distribution (SEDs), we estimate the jet physical parameters of 1392 $γ$-ray-loud active galactic nuclei (AGNs), the largest sample so far. The (SED) jet power and magnetization parameter are derived for these AGNs. Out of these sources, the accretion disk luminosity of 232 sources and (extended) kinetic jet powers of 159 sources are compiled from archived papers. We find the following, (1) Flat-spectrum radio quasars (FSRQs) and BL Lacs are well separated by $Γ=-0.127\log L_γ+8.18$, in $γ$-ray luminosity versus photon index plane with a success rate of 88.6\…
The currents carried by the jets of active galactic nuclei (AGNs) can be probed using maps of the Faraday rotation measure (RM), since a jet current will be accompanied by a toroidal magnetic (B) field, which will give rise to a systematic change in the RM across the jet. The aim of this study is to identify new AGNs displaying statistically significant transverse RM gradients across their parsec-scale jets, and to look for overall patterns in the implied directions for the toroidal B-field components and jet currents. We have carried out new analyses of Faraday RM maps derived from previously…
We select eight nearby AGNs which, based on previous work, appear to be Compton-thin in the line of sight. We model with MYTORUS their broadband X-ray spectra from 20 individual observations with $Suzaku$, accounting self-consistently for Fe K$α$ line emission, as well as direct and scattered continuum from matter with finite column density and solar Fe abundance. Our model configuration allows us to measure the global, out of the line of sight, equivalent hydrogen column density separately from that in the line of sight. For 5 out of 20 observations (in 3 AGNs) we find that the global column …
