A relativistic orbit model for temporal properties of AGN
Prerna Rana, A. Mangalam
备注：
28 pages, 11 figures [24 sub-figures], 6 Tables, final edited version, Accepted in Galaxies; special issue on "X-ray flux and spectral variability of Blazars"
We present a unified model for X-ray quasi-periodic oscillations (QPOs) seen in Narrow-line Seyfert 1 (NLSy1) galaxies, $γ$-ray and optical band QPOs that are seen in Blazars. The origin of these QPOs is attributed to the plasma motion in corona or jets of these AGN. In the case of X-ray QPOs, we applied the general relativistic precession model for the two simultaneous QPOs seen in NLSy1 1H 0707-945 and deduce orbital parameters, such the radius of the emission region, and spin parameter $a$ for a circular orbit; we obtained the Carter's constant $Q$, $a$, and the radius in the case of a spherical orbit solution. In other cases where only one X-ray QPO is seen, we localized the orbital parameters for NLSy1 galaxies REJ 1034+396, 2XMM J123103.2+110648, MS 2254.9-3712, Mrk 766, and MCG-06-30-15. By applying the lighthouse model, we found that a kinematic origin of the jet based $γ$-ray and optical QPOs, in a relativistic MHD framework, is possible. Based on the inbuilt Hamiltonian formulation with a power-law distribution in the orbital energy of the plasma consisting of only circular or spherical trajectories, we show that the resulting Fourier power spectral density (PSD) has a break corresponding to the energy at ISCO. Further, we derive connection formulae between the slopes in the PSD and that of the energy distribution. Overall, given the preliminary but promising results of these relativistic orbit models to match the observed QPO frequencies and PSD at diverse scales in the inner corona and the jet, it motivates us to build detailed models, including a transfer function for the energy spectrum in the corona and relativistic MHD jet models for plasma flow and its polarization properties.
The relativistically broadened Fe K$α$ line, originating from the accretion disc in a vicinity of a super massive black hole, is observed in only less than 50\% of type 1 Active Galactic Nuclei (AGN). In this study we investigate could this lack of detections be explained by the effects of certain parameters of the accretion disc and black hole, such as the inclination, the inner and outer radius of disc and emissivity index. In order to determine how these parameters affect the Fe K $α$ line shape, we simulated about 60,000 Fe K $α$ line profiles emitted from the relativistic disc. Based on s…
Active Galactic Nuclei (AGN) are perfect laboratories to check General Relativity (GR) effects by using Broad Line Region (BLR) clouds eclipses to probe the innermost regions of the accretion disk. A new relativistic X-ray spectral model for X-ray eclipses is introduced. First we present the different observables that are involved in X-ray eclipses, including the X-ray emitting regions size, the emissivity index, the cloud's column density, ionization, size and velocity, the black hole spin, and the system's inclination. Then we highlight some theoretical predictions on the observables by usin…
Radio maps of AGNs often show linear features, called jets, both on pc as well as kpc scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest-frames. The flux boosting due to the relativistic beaming is a very sensitive factor of the jet orientation angle, as seen by the observer. Quite often large bends are seen in these jets, with misalignments being $90^\circ$ or more and might imply a change in the orienta…
We confirm that the spectra are best fit by a model containing two Compton reflection components, one from distant material, and the other displaying relativistic broadening, most likely from the inner accretion disk. The degree of relativistic broadening indicates a preference for high black hole spin, but the reflection is weaker than that expected for a flat disk illuminated by a point source. We investigate the Compton reflection signatures as a function of luminosity, redshift and obscuration, confirming an X-ray Baldwin effect for both the narrow and broad components of the iron line. An…
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…
Linking the central engine to the jet properties in radio loud AGN
我们用14 m Metsähovi毫米波望远镜和甚长基线阵（VLBA）对射电强活动星系核（z < 1）进行了长期观测，并对其中的相对论性喷流参数进行了较好的估计，从而探讨了黑洞质量与其相对论性喷流之间的关系.用北欧光学望远镜（NOT）上的NOTCam拍摄的近红外宿主星系图像和从2MASS全天空巡天中检索的图像使我们能够对样本中的宿主星系进行详细的表面亮度分解，并通过它们的隆起光度估计可靠的黑洞质量。我们目前的黑洞质量和相对论性喷流参数之间的相关性的早期结果。我们的初步结果表明，黑洞的质量越大，它产生的喷流就越快、越亮。
In 2019, the Event Horizon Telescope Collaboration (EHTC) has published the first image of a supermassive black hole (SMBH) obtained via the Very Large Baseline Interferometry (VLBI) technique. In the future, it is expected that additional and more sensitive VLBI observations will be pursued for other nearby Active Galactic Nuclei (AGN), and it is therefore important to understand which possible features can be expected in such images. In this paper, we post-process General Relativistic Magneto-Hydrodynamical (GR-MHD) simulations which include resistivity, thus providing a self-consistent jet …
We present the results of two-temperature magnetohydrodynamic simulations of the propagation of sub-relativistic jets of active galactic nuclei. The dependence of the electron and ion temperature distributions on the fraction of electron heating fe at the shock front is studied for fe=0, 0.05, and 0.2. Numerical results indicate that in sub-relativistic, rarefied jets, the jet plasma crossing the terminal shock forms a hot, two-temperature plasma in which the ion temperature is higher than the electron temperature. The two-temperature plasma expands and forms a backflow referred to as a cocoon…
The enormous sizes and variability of emission of radio-loud AGNs arise from the relativistic flows of plasma along two oppositely directed jets. We use the Athena hydrodynamics code to simulate an extensive suite of 54 propagating three-dimensional relativistic jets with wide ranges of input jet velocities and jet-to-ambient matter density ratios. We determine which parameter sets yield unstable jets that produce jet dominated FR I type radio galaxy morphologies and which tend to produce stable jets with hot-spots and FR II morphologies. Nearly all our simulations involve jets with internal p…
In this paper, we investigate the acceleration in relativistic jets of high-energy proton preaccelerated in the magnetosphere of a supermassive black hole. The proton reaches maximum energy when passing the total potential difference of $U$ between the jet axis and its periphery. This voltage is created by a rotating black hole and transmitted along magnetic field lines into the jet. It is shown that the trajectories of proton in the jet are divided into three groups: untrapped, trapped and not accelerated. Untrapped particles are not kept by poloidal and toroidal magnetic fields inside the je…
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 transverse stratification of active galactic nuclei (AGN) jets is suggested by observations and theoretical arguments, as a consequence of intrinsic properties of the central engine (accretion disc + black hole) and external medium. On the other hand, the one-component jet approaches are heavily challenged by the various observed properties of plasmoids in radio jets (knots), often associated with internal shocks. Given that such a transverse stratification plays an important role on the jets acceleration, stability, and interaction with the external medium, it should also induce internal …
Active galactic nuclei (AGN) show a range of morphologies and dynamical properties, which are determined not only by parameters intrinsic to the central engine but also their interaction with the surrounding environment. We investigate the connection of kiloparsec scale AGN jet properties to their intrinsic parameters and surroundings. This is done using a suite of 40 relativistic hydrodynamic simulations spanning a wide range of engine luminosities and opening angles. We explore AGN jet propagation with different ambient density profiles, including $r^{-2}$ (self-similar solution) and $r^{-1}…
Active galactic nuclei (AGN) are powered by the accretion of disks of gas onto supermassive black holes (SMBHs). Stars and stellar remnants orbiting the SMBH in the nuclear star cluster (NSC) will interact with the AGN disk. Orbiters plunging through the disk experience a drag force and, through repeated passage, can have their orbits captured by the disk. A population of embedded objects in AGN disks may be a significant source of binary black hole mergers, supernovae, tidal disruption events and embedded gamma-ray bursts. For two representative AGN disk models we use geometric drag and Bondi…
FERO: Finding Extreme Relativistic Objects. I. Statistics of Relativistic Fe Kalpha lines in Radio-Quiet Type 1 AGN
吸积模型预测，相对论效应增宽的荧光线应该是由X射线辐射反射到活动星系核（AGN）中心黑洞周围吸积盘的内部区域引起的。相对论性线的起源背后的理论已经很好地建立起来，来自中等数量来源的观测证据似乎支持这些线的存在。本工作的目的是建立活动星系核的相对论Fe K α线的分数，并研究可能的相关性与源的物理性质。为了寻找Fe K α线相对论展宽的重要证据，对149个射电宁静的1型活动星系核（AGN）进行了系统和统一的分析。为便于进行统计研究，确定了一个几乎完整的、通量有限的31个来源的子样本。的2-10 keV的FERO源的光谱进行了比较，一个复杂的模型，其中包括在塞弗特星系的X射线光谱中观察到的物理成分：一个幂律的主要连续修改的非相对论康普顿反射和暖吸收，加上一系列的窄Fe线反射功能。在通量限制的样品中，观察到的相对论性Fe K α线的显著证据的源的分数为36%。平均线等效宽度（EW）为100 eV的量级，而平均盘倾斜角为28+/-5度，径向盘发射率定律的平均功率定律指数为2.4+/-0.4。自旋值仅在两种情况下（MCG-6-30-15和MRK 509）得到了很好的约束，而在其余情况下，只要可以设置约束，它总是意味着拒绝静态黑洞解。Fe K α线EW与盘参数或系统物理性质（如黑洞质量、吸积率和硬X射线光度）无关。
The primary X-ray emission from AGN, described by a power law, irradiates the accretion disc producing reflection features in the spectrum. The reflection features arising from the inner regions of the disc can be significantly modified by the relativistic effects near the black hole. We investigate the relationship between the relativistic reflection fraction $R_f$, defined as the ratio of the coronal intensity that illuminates the accretion disc to the coronal intensity observed directly, and the hard X-ray photon index $Γ$ of a NuSTAR sample of Seyfert 1 galaxies. The X-ray spectra are mode…
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…
Electron-positron cascade in magnetospheres of supermassive Kerr black holes and the origin of relativistic AGN jets
University of Kansas（堪萨斯大学）；Massachusetts Institute of Technology（麻省理工学院）；Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文中心）
Active Galactic Nuclei (AGN) and their relativistic jets are believed to be potential sites of ultra-high-energy (UHE) cosmic ray acceleration. This paper reviews basic observational findings as well as requirements on source energetics, and then discusses the relevance of different acceleration sites and mechanisms, such as black hole gap, shock in back-flows or jet shear acceleration. When put in context, the result suggests that Fermi-type particle acceleration at trans-relativistic shocks and/or in shearing, relativistic flows offers the most promising framework for UHECR production in AGN…
Observational Properties of Thermal Emission from Relativistic Jets Embedded in AGN Disks
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Department of Astronomy, School of Physical Sciences, University of Science and Technology of China（中国科学技术大学物理学院天文学系）
Accreting black holes produce collimated outflows, or jets, that traverse many orders of magnitude in distance, accelerate to relativistic velocities, and collimate into tight opening angles. Of these, perhaps the least understood is jet collimation due to the interaction with the ambient medium. In order to investigate this interaction, we carried out axisymmetric general relativistic magnetohydrodynamic simulations of jets produced by a large accretion disc, spanning over 5 orders of magnitude in time and distance, at an unprecedented resolution. Supported by such a disc, the jet attains a p…
The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGN) is one of the key questions to understand the nature of AGN jets. However, little is known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar 3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama Large Millimeter/submillimeter Ar…
The disks of Active Galactic Nuclei (AGNs), traditionally studied as the feeders of the supermassive black holes (SMBHs) at their centers, have recently triggered a lot of interest also as hosts to massive stars and hence their neutron star (NS) and black hole (BH) remnants. Migration traps and gas torques in these disks favor binary formation and enhance the rate of compact object mergers. In these environments both long gamma-ray bursts (GRBs) from the death of massive stars and short GRBs from NS-NS and NS-BH mergers are expected. However, their properties in the unique environments of AGN …
In the paper we study the process of excitation of Langmuir waves in the magnetospheres of active galactic nuclei (AGN), by taking a general-relativistic expression of the Goldreich-Julian density into account. We considered the linearised set of equations which describe dynamics of the studied mechanism: the Euler equation, the continuity equation and the Poisson equation. After solving the dispersion relation and obtaining the instability growth rate, we explored it versus several physical parameters: electron's and proton's relativistic factors and the mass and luminosity of AGN, which are …
High-energy emission of extragalactic objects is known to take place in relativistic jets, but the nature, the location, and the emission processes of the emitting particles are still unknown. One of the models proposed to explain the formation of relativistic ejections and their associated non-thermal emission is the two-flow model, where the jets are supposed to be composed of two different flows, a mildly relativistic baryonic jet surrounding a fast, relativistically moving electron-positron plasma. Here we present the simulation of the emission of such a structure taking into account the m…
General relativistic ray tracing simulations of the time-averaged spectrum and energy-dependent time delays in AGN are presented. We model the lamp-post geometry in which the accreting gas is illuminated by an X-ray source located on the rotation axis of the black hole. The spectroscopic features imprinted in the reflection component are modelled using REFLIONX. The associated time delays after the direct continuum, known as reverberation lags, are computed including the full effects of dilution and ionization gradients on the disc. We perform, for the first time, simultaneous fitting of the t…
This volume presents an overview of selected aspects of physical processes occurring in the inner regions of Active Galactic Nuclei (AGN). The observational evidence suggests that strong gravitational fields play a significant role in governing the energy output of AGN and their influence on the surrounding medium, possibly due to the presence of a supermassive black hole. In order to reduce an unnecessary overlap with numerous reviews on the subject of AGN, here we focus on several selected topics.
The origin of the extended X-ray emission in the large-scale jets of active galactic nuclei (AGNs) poses challenges to conventional models of acceleration and emission. Although the electron synchrotron radiation is considered the most feasible radiation mechanism, the formation of the continuous large-scale X-ray structure remains an open issue. As astrophysical jets are expected to exhibit some turbulence and shearing motion, we here investigate the potential of shearing flows to facilitate an extended acceleration of particles and evaluate its impact on the resultant particle distribution. …
In this paper we lay out a simple set of relationships connecting the dynamics of fast plasma jets to the dynamical state of their ambient media. The objective is to provide a tool kit that can be used to connect the morphologies of radio AGNs in galaxy clusters to the dynamical state of the local ICM. The formalism is intended to apply to jets whether they are relativistic or non-relativistic. Special attention is paid to interactions involving ICM shocks, although the results can be applied more broadly. Our formalism emphasizes the importance of the relative Mach number of the impacting ICM…
High-energy cosmic rays (CRs) can be accelerated in the relativistic jets of Active Galactic Nuclei (AGNs) powered by supermassive black holes. The baryon loading efficiency onto relativistic CR baryons from the accreting black holes is poorly constrained by observations so far. In this paper, we suggest that the $γ$-ray emission of galaxy clusters can be used to study the baryon loading factor of AGN jets, since CRs injected by AGN jets are completely confined in the galaxy clusters and sufficiently interact with intra-cluster medium via hadronic process, producing diffuse $γ$-rays. We study …
