Evidence for a maximum jet efficiency for the most powerful radio galaxies
Cristina A. C. Fernandes, Matt J. Jarvis, Steve Rawlings, Alejo Martinez-Sansigre, Evanthia Hatziminaoglou, Mark Lacy, Mat J. Page, Jason A. Stevens, Eleni Vardoulaki
备注：
9 pages, 4 figures. Accepted for publication in MNRAS
We use new mid-infrared (mid-IR) photometry from the Spitzer Space Telescope to study the relations between low-frequency radio luminosity density L_151MHz, mid-IR (12um rest-frame) luminosity L_12um, and optical-emission-line ([OII]) luminosity L_[OII], for a complete sample of z~1 radio galaxies from the 3CRR, 6CE, 6C*, 7CRS and TOOT00 surveys. The narrow redshift span of our sample (0.9<z<1.1) means that it is unbiased to evolutionary effects. We find evidence that these three quantities are positively correlated. The scaling between L_12um and L_[OII] is similar to that seen in other AGN samples, consistent with both L_12um and L_[OII] tracing accretion rate. We show that the positive correlation between L_12um and L_151MHz implies that there is a genuine lack of objects with low values of L_12um at high values of L_151MHz. Given that L_12um traces accretion rate, while L_151MHz traces jet power, this can be understood in terms of a minimum accretion rate being necessary to produce a given jet power. This implies that there is a maximum efficiency with which accreted energy can be chanelled into jet power and that this efficiency is of order unity.
Jet re-orientation associated with the time evolution of radio quasars explains the formation of X-shaped radio galaxies and their preference for isolated environments. But since X-shaped radio galaxies are generally not found in dense environments (e.g. groups/clusters), the jet re-orientation phenomenon for radio galaxies in groups and clusters has been ignored. We take a closer look at the re-orientation of FRI jets with respect to FRII jets, and find that it may constitute the as-yet unidentified trigger for star formation suppression in radio galaxies. We show how the recently explored ra…
We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is …
Jets of compact radio sources are highly relativistic and Doppler boosted, making studies of their intrinsic properties difficult. Observed brightness temperatures can be used to study the intrinsic physical properties of the relativistic jets, and constrain models of jet formation in the inner jet region. We aim to observationally test such inner jet models. The very long baseline interferometry (VLBI) cores of compact radio sources are optically thick at a given frequency. The distance of the core from the central engine is inversely proportional to the frequency. Under the equipartition con…
The distinctive morphology of head-tail radio galaxies reveals strong interactions between the radio jets and their intra-cluster environment, the general consensus on the morphology origin of head-tail sources is that radio jets are bent by violent intra-cluster weather. We demonstrate in this paper that such strong interactions provide a great opportunity to study the jet properties and also the dynamics of intra-cluster medium (ICM). By three-dimensional magnetohydrodynamical simulations, we analyse the detailed bending process of a magnetically dominated jet, based on the magnetic tower je…
We have carried out numerical hydrodynamic simulations of radio jets from active galactic nuclei using the PLUTO simulation code, with the aim of investigating the effect of different environments and intermittency of energy injection on the resulting dynamics and observable properties of the jet-inflated lobes. Initially conical jets are simulated in poor group and cluster environments. We show that the environment into which a radio jet is propagating plays a large role in the resulting morphology, dynamics and observable properties of the radio source. The same jet collimates much later in …
Our view of the properties of extragalactic radio jets and the impact they have on the host galaxy has expanded in the recent years. This has been possible thanks to the data from new or upgraded radio telescopes. This review briefly summarises the current status of the field and describes some of the exciting recent results and the surprises they have brought. In particular, the physical properties of radio jets as function of their radio power will be discussed together with the advance made in understanding the life-cycle of radio sources. The evolutionary stage (e.g. newly born, dying, res…
Up to now, jet kinematic studies of radio quasars have barely reached beyond the redshift range at $z>3.5$. This significantly limits our knowledge of high-redshift jets, which can provide key information for understanding the jet nature and the growth of the black holes in the early Universe. In this paper, we selected 9 radio-loud quasars at $z>3.5$ which display milliarcsec-scale jet morphology. We provided evidence on the source nature by presenting high-resolution very long baseline interferometry (VLBI) images of the sample at 8.4~GHz frequency and making spectral index maps. We also con…
Radio-loud quasars (RLQs) are more X-ray luminous than predicted by the X-ray-optical/UV relation (i.e. $L_\mathrm{x}\propto L_\mathrm{uv}^γ$) for radio-quiet quasars (RQQs). The excess X-ray emission depends on the radio-loudness parameter ($R$) and radio spectral slope ($α_\mathrm{r}$). We construct a uniform sample of 729 optically selected RLQs with high fractions of X-ray detections and $α_\mathrm{r}$ measurements.We find that steep-spectrum radio quasars (SSRQs; $α_\mathrm{r}\le-0.5$) follow a quantitatively similar $L_\mathrm{x}\propto L_\mathrm{uv}^γ$ relation as that for RQQs, suggest…
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…
Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the sub-parsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near-IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio gala…
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 …
A number of works reported on the existence of a large scale alignment of the polarization plane of extragalactic sources as well as the alignment of radio-sources structural axes. However, both claims and their interpretation remain controversial. For the first time we explore the parsec-scale jets alignments. Additionally, we use archival polarimetric data at different wavelengths in order to compare relative orientations of the jets and the polarization planes of their emission. Using the flux density distribution in very long baseline interferometry (VLBI) radio maps from the Astrogeo data…
We explore the possibility to detect the continuum radio signal from direct collapse black holes (DCBHs) by upcoming radio telescopes such as the SKA and ngVLA, assuming that after formation they can launch and sustain powerful jets at the accretion stage. We assume that the high-$z$ DCBHs have similar jet properties as the observed radio-loud AGNs, then use a jet model to predict their radio flux detectability. If the jet power $P_{\rm jet}\gtrsim10^{42-43}$ erg s$^{-1}$, it can be detectable by SKA/ngVLA, depending on the jet inclination angle. Considering the relation between jet power and …
This paper theoretically investigates the relations between the structure of relativistic jets and produced synchrotron images, by using a steady axisymmetric force-free jet model. We especially focus on the limb-brightened jets that are largely symmetric to the jet axes and observed in some active galactic nuclei such as M87, Mrk~501, Cyg~A, and 3C84. We find that symmetrically limb-brightened images can be produced when magnetic field lines of the jet penetrate a fast-spinning black hole as motivated by the Blandford-Znajek mechanism. On the other hand, jets with magnetic field lines that pa…
Protostellar jets and outflows are pointers of star-formation and serve as important sources of momentum and energy transfer to the interstellar medium. Radio emission from ionized jets have been detected towards a number of protostellar objects. In few cases, negative spectral indices and polarized emission have also been observed suggesting the presence of synchrotron emission from relativistic electrons. In this work, we develop a numerical model that incorporates both thermal free-free and non-thermal synchrotron emission mechanisms in the jet geometry. The flux densities include contribut…
Radio emission from protostellar jets is usually dominated by free-free emission from thermal electrons. However, in some cases, it has been proposed that non-thermal emission could also be present. This additional contribution from non-thermal emission has been inferred through negative spectral indices at centimeter wavelengths in some regions of the radio jets. In the case of HH 80-81, one of the most powerful protostellar jets known, linearly polarized emission has also been detected, revealing that the non-thermal emission is of synchrotron nature from a population of relativistic particl…
Compact radio cores associated with relativistic jets are often observed in both active galactic nuclei and X-ray binaries. Their radiative properties follow some general scaling laws which primarily depend on their masses and accretion rates. However, it has been suggested that the black hole spin can also strongly influence the power and radio flux of these. Here, we attempt to estimate the dependency of the radio luminosity of steady jets launched by accretion disks on black hole mass, accretion rate and spin using numerical simulations. We make use of 3D GRMHD simulations of accretion disk…
Here we report on the total-intensity 610 MHz GMRT observations of the peculiar hybrid blazar SBS B1646+499, which merges the properties of BL Lacertae objects and flat-spectrum radio quasars. The complex radio structure of SBS B1646+499, emerging from the archival radio data and our new GMRT observations, consists of the Mpc-scale, elongated halo, the unilateral kpc-scale jet, and the nuclear jet extending up to 20pc from the compact core. The giant halo is characterized by a steep radio spectrum, indicative of the advanced ageing of the electron population within the lobes. For the large-sca…
We study the effect of variable jet bulk Lorentz factors, i.e., either jet acceleration or deceleration, on partially synchrotron self-absorbed radio spectra from cores of radio-loud active galactic nuclei and black-hole binaries in the hard state. In about a half of quasars and radio galaxies, their core radio spectra are observed to be soft, i.e., have the spectral index of $α<0$. If they are emitted by jets with constant Lorentz factors, that softness implies deposition of large amounts of energy at large distances from the centre. We show here that such soft spectra can be explained withou…
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…
We report multi-epoch Very Long Baseline Interferometric (VLBI) observations of the compact radio lobe in the radio galaxy 3C84 (NGC1275) during 2016 - 2020. The image sequence of 3C84 reveals that the hotspot in the radio lobe showed the one-year long frustration in 2017 within a compact region of about 0.07 parsec, suggesting a strong collision between the jet and a compact dense cloud with the estimated average density about $(4\-- 6)\times 10^{5}~{\rm cm^{-3}}$. Although the hotspot and the radio lobe began to move south again after its breakout, the radio lobe showed a morphological trans…
We present simultaneous multi-band radio and X-ray observations of the black hole X-ray binary Cygnus X-1, taken with the Karl G. Jansky Very Large Array and the Nuclear Spectroscopic Telescope Array. With these data, we detect clear flux variability consistent with emission from a variable compact jet. To probe how the variability signal propagates down the jet flow, we perform detailed timing analyses of our data. We find that the radio jet emission shows no significant power at Fourier frequencies $f\gtrsim0.03$ Hz (below $\sim30$ sec timescales), and that the higher frequency radio bands (…
We report a 3D MHD simulation study of the interactions between radio galaxies and galaxy-cluster-media shocks in which the incident shock normals are orthogonal to the bipolar AGN jets. Before shock impact, light, supersonic jets inflate lobes (cavities) in a static, uniform ICM. We examine three AGN activity scenarios: 1) continued, steady jet activity; 2) jet source cycled off coincident with shock/radio lobe impact; 3) jet activity ceased well before shock arrival (a "radio phoenix" scenario). The simulations follow relativistic electrons (CRe) introduced by the jets, enabling synthetic ra…
Observations of radio loud active galaxies in the XMM-Newton archive by Mehdipour & Costantini show a strong anti-correlation between the column density of the ionized wind and the radio loudness parameter, providing evidence that jets may thrive in thin disks. This is in contrast with decades of analytic and numerical work suggesting jet formation is contingent on the presence of an inner, geometrically thick disk structure, which serves to both collimate and accelerate the jet. Thick disks emerge in radiatively inefficient disks which are associated with sub-Eddington as well as super-Edding…
We report on the JVLA observations of three high redshift Active Galactic Nuclei (AGN), having a black hole mass estimated to be among the largest known. Two of them, SDSS J0100+2802 and SDSS J0306+1853 at redshift 6.326 and 5.363 respectively, are radio-quiet AGN according to the classic definition, while the third (B2 1023+25 at z=5.284) is a powerful blazar. The JVLA data clearly show a radio structure in the first source, and a radio emission with a relatively steep radio spectrum in the second one, demonstrating the presence of a radio jet and a diffuse component. Therefore, being radio-q…
Dozens of stellar tidal disruption events (TDEs) have been identified at optical, UV and X-ray wavelengths. A small fraction of these, most notably Swift J1644+57, produce radio synchrotron emission, consistent with a powerful, relativistic jet shocking the surrounding circumnuclear gas. The dearth of similar non-thermal radio emission in the majority of TDEs may imply that powerful jet formation is intrinsically rare, or that the conditions in galactic nuclei are typically unfavorable for producing a detectable signal. Here we explore the latter possibility by constraining the radial profile …
We present results from two suites of simulations of powerful radio galaxies in poor cluster environments, with a focus on the formation and evolution of the radio lobes. One suite of models uses relativistic hydrodynamics and the other relativistic magnetohydrodynamics; both are set up to cover a range of jet powers and velocities. The dynamics of the lobes are shown to be in good agreement with analytical models and with previous numerical models, confirming in the relativistic regime that the observed widths of radio lobes may be explained if they are driven by very light jets. The ratio of…
TeV gamma rays are observed from a few nearby radio galaxies whose jets are viewed at relatively large angles towards the observer. This emission can be produced in the kpc scale jets whose Lorentz factors are decelerated from values of the order of several at the parsec scale distances. We consider in detail the model in which TeV gamma-ray emission is produced by the relativistic electrons in the kpc scale jet which comptonize strongly beamed radiation from the inner (parsec scale) jet. As an example, we study morphology of the TeV gamma-ray emission from the decelerated kpc scale jet in the…
The tidal disruption of a star by a supermassive black hole can result in transient radio emission. The electrons producing these synchrotron radio flares could either be accelerated inside a relativistic jet or externally by shocks resulting from an outflow interacting with the circumnuclear medium. Until now, evidence for the internal emission mechanism has been lacking; nearly all tidal disruption flare studies have adopted the external shock model to explain the observed properties of radio flares. Here we report a result that presents a challenge to external emission models: we discovered…
