arXiv subjects

Manel Perucho

Publications and source records attributed to Manel Perucho.

At least 19 recordsLinked to original sources

arXiv2026

AGN Jets from Formation to Dissipation

Active Galactic Nuclei (AGN) are among the most energetic phenomena in the Universe, capable of launching powerful relativistic jets that extend from sub-parsec to megaparsec scales. These jets play a crucial role in regulating star formation, redistributing energy and matter, and shaping the evolution of galaxies and their environments. Despite decades of study, a comprehensive understanding of how AGN jets form, propagate, and dissipate remains elusive. The aim of this chapter is to highlight how the future capabilities of the the Square Kilometre Array (SKA), as a standalone array as well as in combination with Very Long Baseline Interferometry (VLBI) arrays and multi-wavelength facilities, will transform our capabilities to study the co-evolution of AGN jets and their host galaxies from jet formation to dissipation scales.

astro-ph.GA↗

arXiv2025

AGN hosting jets. I: A semi-analytical model for the evolution of radio galaxies

Three-dimensional simulations of relativistic jets are a useful tool to understand the evolution of jets and radio galaxies in detail. However, computationally demanding as they are, their use is limited to a relatively small number of representative cases. When comparing to the distribution of large samples of objects in the luminosity-distance plane (P-D plane), the most efficient approach is to use analytical or semi-analytical models that reproduce the evolution of the main parameters governing the dynamics and radio luminosity of the sources. Our aim is to build a semi-analytical model that allows us to produce mock samples of radio galaxies to be compared with real populations and use this approach to constrain the general properties of active galaxies with jets in a cosmological context. In this work, we present a new model for the evolution of radio galaxies based on the resolution of ordinary differential equations and inspired both by previous experience on numerical simulations of jets across several orders of magnitude in power, and by observational evidence. Our results show remarkable agreement between the results given by the semi-analytical model and those obtained by both 2D and 3D relativistic hydrodynamics simulations of jets ranging from 1.e35 W to 1.e39 W. From the derived trajectories of powerful radio galaxies through the P-D diagram (powers greater than 1.e36 W), our model agrees with typical lifetimes of galactic activity of < 500 Myr. We also compare our results with previous models in the literature. In a follow-up paper, we use this model to generate mock populations of radio galaxies at low redshifts and compare them to the LoTSS sample.

astro-ph.CO↗

arXiv2025

Millimeter VLBI constraints on the central magnetic field and symmetric jet production in the twin-jet galaxy NGC 1052

This paper investigates the symmetry and magnetic field properties of the jets in the radio galaxy NGC 1052, with particular attention to the impact of the ionized torus that surrounds the central region on the emitted radiation. Our study is based on three new 43 GHz Very-Long-Baseline Interferometry (VLBI) observations and one 86 GHz observation conducted between April 2021 and April 2022. We derive key jet parameters, such as speed, width, and flux density for both jets at the two frequencies and compare them with those obtained from previous VLBI campaigns. Additionally, we present the first (43-86) GHz spectral index image of NGC 1052, which is crucial to assess the role of the torus at high frequencies. Finally, we leverage the derived observational parameters to constrain the magnetic field strength and configuration in the launched jets. We observe variability in the jet morphology at 43 GHz across the three epochs, which can be associated with the propagation of jet knots launched from the nuclear region. The stacked 43 GHz image reveals that the western and receding jet is approximately three times fainter than its eastern (approaching) counterpart in the sub-mas region. This asymmetry, together with the (43-86) GHz spectral index map, suggests that free-free absorption may affect the 43 GHz emission. On the contrary, the jets appear highly symmetric at 86 GHz. From the stacked images at 43 GHz and 86 GHz, we extract the jet width, which is consistent with previous VLBI studies and supports the presence of a parabolic jet profile on very compact scales. Overall, our results suggest that the jets are intrinsically launched symmetrically, and that the observed time-dependent asymmetries may result from free-free absorption by the torus and the downstream propagation of jet components, a scenario supported by previous theoretical studies.

astro-ph.HE↗

arXiv2025

The putative center in NGC 1052

Many active galaxies harbor powerful relativistic jets, however, the detailed mechanisms of their formation and acceleration remain poorly understood. To investigate the area of jet acceleration and collimation with the highest available angular resolution, we study the innermost region of the bipolar jet in the nearby low-ionization nuclear emission-line region (LINER) galaxy NGC 1052. We combined observations of NGC 1052 taken with VLBA, GMVA, and EHT over one week in the spring of 2017. For the first time, NGC 1052 was detected with the EHT, providing a size of the central region in-between both jet bases of 250 RS (Schwarzschild radii) perpendicular to the jet axes. This size estimate supports previous studies of the jets expansion profile which suggest two breaks of the profile at around 300 RS and 10000 RS distances to the core. Furthermore, we estimated the magnetic field to be 1.25 Gauss at a distance of 22 {\mu}as from the central engine by fitting a synchrotron-self absorption spectrum to the innermost emission feature, which shows a spectral turn-over at about 130 GHz. Assuming a purely poloidal magnetic field, this implies an upper limit on the magnetic field strength at the event horizon of 26000 Gauss, which is consistent with previous measurements. The complex, low-brightness, double-sided jet structure in NGC 1052 makes it a challenge to detect the source at millimeter (mm) wavelengths. However, our first EHT observations have demonstrated that detection is possible up to at least 230 GHz. This study offers a glimpse through the dense surrounding torus and into the innermost central region, where the jets are formed. This has enabled us to finally resolve this region and provide improved constraints on its expansion and magnetic field strength.

astro-ph.HE↗

arXiv2024

Dynamic and Radiative Implications of Jet-Star Interactions in AGN Jets

The interactions between jets from active galactic nuclei (AGN) and their stellar environments significantly influence jet dynamics and emission characteristics. In low-power jets, such as those in Fanaroff-Riley I (FR I) galaxies, the jet-star interactions can notably affect jet deceleration and energy dissipation. Recent numerical studies suggest that mass loading from stellar winds is a key factor in decelerating jets, accounting for many observed characteristics in FR I jets. Additionally, a radio-optical positional offset has been observed, with optical emission detected further down the jet than radio emission. This observation may challenge traditional explanations based solely on recollimation shocks and instabilities. This work utilizes the radiative transfer code RIPTIDE to generate synthetic synchrotron maps, from a population of re-accelerated electrons, in both radio and optical bands from jet simulations incorporating various mass-loading profiles and distributions of gas and stars within the ambient medium. Our findings emphasize the importance of mass entrainment in replicating the extended and diffuse radio/optical emissions observed in FR I jets and explaining the radio-optical offsets. These offsets are influenced by the galaxy's physical properties, the surrounding stellar populations, and observational biases. We successfully reproduce typical radio-optical offsets by considering a mass-load equivalent to $10^{-9}~M_\odot \cdot \rm{yr}^{-1} \cdot \rm{pc}^{-3}$. Overall, our results demonstrate that positive offset measurements are a promising tool for revealing the fundamental properties of galaxies and potentially their stellar populations, particularly in the context of FR I jets.

astro-ph.HE↗

arXiv2024

Probing jet dynamics and collimation in radio galaxies. Application to NGC 1052

Context. Radio galaxies with visible two-sided jet structures, such as NGC 1052, are sources of particular interest to study the collimation and shock structure of active galactic nuclei jets. High-resolution very-long-baseline interferometry observations of such sources can resolve and study the jet collimation profile and probe different physical mechanisms. Aims. In this paper, we study the physics of double-sided radio sources at parsec scales, and in particular investigate whether propagating shocks can give rise to the observed asymmetry between jet and counterjet. Methods. We carry out special relativistic hydrodynamic simulations and perform radiative transfer calculations of an over-pressured perturbed jet. During the radiative transfer calculations we incorporate both thermal and nonthermal emission while taking the finite speed of light into account. To further compare our results to observations, we create more realistic synthetic data including the properties of the observing array as well as the image reconstruction via multifrequency regularized maximum likelihood methods. We finally introduce a semi-automatized method for tracking jet components and extracting jet kinematics. Results. We show that propagating shocks in an inherently symmetric double-sided jet can lead to partially asymmetric jet collimation profiles due to time delay effects and relativistic beaming. These asymmetries may appear on specific epochs, with one jet evolving near conically and the other one parabolically (width profile evolving with a slope of 1 and 0.5, respectively). However, these spurious asymmetries are not significant when observing the source evolve for an extended amount of time. Conclusions. Purely observational effects are not enough to explain a persisting asymmetry in the jet collimation profile of double-sided jet sources and hint at evidence for asymmetrically launched jets.

astro-ph.HE↗

arXiv2024

Shocks, clouds and atomic outflows in active galactic nuclei hosting relativistic jets

A number of observations have revealed atomic and/or molecular lines in active galaxies hosting jets and outflows. Line widths indicate outward motions of hundreds to few thousands of kilometers per second. They appear associated to the presence of radio emission in Gigahert-peaked spectrum (GPS) and compact steep spectrum (CSS) sources, with linear sizes < 10 kpc. Numerical simulations have shown that the bow shocks triggered by relativistic jets in their host galaxies drive ionisation and turbulence in the interstellar medium (ISM). However, the presence of atomic lines requires rapid recombination of ionised gas, which seems to be hard to explain from the physical conditions revealed so far by numerical simulations of powerful jets. The aim of this paper is to provide a global frame to explain the presence of lines in terms of jet and shock evolution, and fix the parameter space in which the atomic and molecular outflows might occur. This parameter space is inspired by numerical simulations and basic analytical models of jet evolution as a background. Our results show that a plausible, general explanation involves momentum transfer and heating to the interstellar medium gas by jet triggered shocks within the inner kiloparsecs. The presence of post-shock atomic gas is possible in the case of shocks interacting with dense clouds that remain relatively stable after the shock passage. According to our results, current numerical simulations cannot reproduce the physical conditions to explain the presence of atomic and molecular outflows in young radio-sources. However, I show that these outflows might occur in low-power jets at all scales, and predict a trend towards powerful jets showing lines at CSS scales, when clouds have cooled to recombination temperatures.

astro-ph.HE↗

arXiv2023

Filamentary structures as the origin of blazar jet radio variability

Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very long baseline interferometric (VLBI) observations of blazars have revealed only funnel-like morphologies with little information of the ejected plasma internal structure, or lacked the sufficient dynamic range to reconstruct the extended jet emission. Here we show microarcsecond-scale angular resolution images of the blazar 3C 279 obtained at 22 GHz with the space VLBI mission RadioAstron, which allowed us to resolve the jet transversely and reveal several filaments produced by plasma instabilities in a kinetically dominated flow. Our high angular resolution and dynamic range image suggests that emission features traveling down the jet may manifest as a result of differential Doppler-boosting within the filaments, as opposed to the standard shock-in-jet model invoked to explain blazar jet radio variability. Moreover, we infer that the filaments in 3C 279 are possibly threaded by a helical magnetic field rotating clockwise, as seen in the direction of the flow motion, with an intrinsic helix pitch angle of ~45 degrees in a jet with a Lorentz factor of ~13 at the time of observation.

astro-ph.HE↗

arXiv2023

Numerical simulations of relativistic jets

In this paper, we review recent and ongoing work by our group on numerical simulations of relativistic jets. Relativistic outflows in Astrophysics are related to dilute, high energy plasmas, with physical conditions out of the reach of current laboratory capabilities. Simulations are thus imperative for the study of these objects. We present a number of such scenarios that have been studied by our group at the Universitat de Val\`encia. In particular, we have focused on the evolution of extragalactic outflows through galactic and intergalactic environments, deceleration by interaction with stars or clouds, or the propagation of jets in X-ray binaries and interaction with stellar winds from massive companions. All also share their role as particle acceleration sites and production of non-thermal radiation throughout the electromagnetic spectrum. Therefore, our work is not only aimed to understand the impact of outflows on their environments and thus their role in galaxy and cluster evolution, but also the nature and capabilities of these sites as generators of high and very-high energy radiation and cosmic rays.

astro-ph.HE↗

arXiv2023

On the large scale morphology of Hercules A: destabilized hot jets?

Extragalactic jets are generated as bipolar outflows at the nuclei of active galaxies. Depending on their morphology, they are classified as Fanaroff-Riley type I (centre-brightened) and Fanaroff-Riley type II (edge-brightened) radio jets. However, this division is not sharp and observations of these sources at large scales often show intermediate jet morphologies or even hybrid jet morphologies with a FRI type jet on one side and a FRII type jet on the other. A good example of a radio galaxy that is difficult to classify as FRI or FRII is Hercules~A. This source shows jets with bright radio lobes (a common feature of FRII type jets) albeit without the hotspots indicative of the violent interaction between the jet and the ambient medium at the impact region, because the jets seem to be disrupted inside the lobes at a distance from the bow shocks surrounding the lobes. In this paper, we explore the jet physics that could trigger this peculiar morphology by means of three-dimensional relativisitic hydrodynamical simulations. Our results show that the large-scale morphological features of Hercules A jets and lobes can be reproduced by the propagation of a relativistically hot plasma outflow that is disrupted by helical instability modes, and generates a hot lobe that expands isotropically against the pressure-decreasing intergalactic medium. We also discuss the implications that this result may have for the host active nucleus in terms of a possible transition from high-excitation to low-excitation galaxy modes.

astro-ph.HE↗

arXiv2022

On the application of Jacobian-free Riemann solvers for relativistic radiation magnetohydrodynamics under M1 closure

Radiative transfer plays a major role in high-energy astrophysics. In multiple scenarios and in a broad range of energy scales, the coupling between matter and radiation is essential to understand the interplay between theory, observations and numerical simulations. In this paper, we present a novel scheme for solving the equations of radiation relativistic magnetohydrodynamics within the parallel code L\'ostrego. These equations, which are formulated taking successive moments of the Boltzmann radiative transfer equation, are solved under the gray-body approximation and the M1 closure using an IMEX time integration scheme. The main novelty of our scheme is that we introduce for the first time in the context of radiation magnetohydrodynamics a family of Jacobian-free Riemann solvers based on internal approximations to the Polynomial Viscosity Matrix, which were demonstrated to be robust and accurate for non-radiative applications. The robustness and the limitations of the new algorithms are tested by solving a collection of one-dimensional and multi-dimensional test problems, both in the free-streaming and in the diffusion radiation transport limits. Due to its stable performance, the applicability of the scheme presented in this paper to real astrophysical scenarios in high-energy astrophysics is promising. In future simulations, we expect to be able to explore the dynamical relevance of photon-matter interactions in the context of relativistic jets and accretion discs, from microquasars and AGN to gamma-ray bursts.

astro-ph.HE↗

arXiv2022

Magnetization of Relativistic Current-Carrying Jets with Radial Velocity Shear

Astrophysical jets, launched from the immediate vicinity of accreting black holes, carry away large amounts of power in a form of bulk kinetic energy of jet particles and electromagnetic flux. Here we consider a simple analytical model for relativistic jets at larger distances from their launching sites, assuming a cylindrical axisymmetric geometry with a radial velocity shear, and purely toroidal magnetic field. We argue that, as long as the jet plasma is in magnetohydrostatic equilibrium, such outflows tend to be particle dominated, i.e. the ratio of the electromagnetic to particle energy flux, integrated over the jet cross-sectional area, is typically below unity, $\sigma < 1$. At the same time, for particular magnetic and radial velocity profiles, magnetic pressure may still dominate over particle pressure for certain ranges of the jet radius, i.e. the local jet plasma parameter $\beta_{pl} < 1$, and this may be relevant in the context of particle acceleration and production of high-energy emission in such systems. The jet magnetization parameter can be elevated up to the modest values $\sigma \lesssim \mathcal{O}(10)$ only in the case of extreme gradients or discontinuities in the gaseous pressure, and a significantly suppressed velocity shear. Such configurations, which consist of a narrow, unmagnetized jet spine surrounded by an extended, force-free layer, may require an additional poloidal field component to stabilize them against current-driven oscillations, but even this will not elevate substantially their $\sigma$ parameter.

astro-ph.HE↗

arXiv2021

Reading M87's DNA: A Double Helix revealing a large scale Helical Magnetic Field

We present unprecedented high fidelity radio images of the M87 jet. We analyzed Jansky Very Large Array (VLA) broadband, full polarization, radio data from 4 to 18 GHz. The observations were taken with the most extended configuration (A configuration), which allow the study of the emission of the jet up to kpc scales with a linear resolution $\sim$10 pc. The high sensitivity and resolution of our data allow to resolve the jet width. We confirm a double-helix morphology of the jet material between $\sim$300 pc and $\sim$1 kpc. We found a gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges, and a gradient in the Faraday depth with opposite signs at the jet edges. We also found that the behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole although the jet is most likely particle dominated at these large scales. Therefore, we propose a plausible scenario in which the helical configuration of the magnetic field has been maintained to large scales thanks to the presence of Kelvin-Helmholtz instabilities.

astro-ph.GA↗

arXiv2021

Long-term FRII jet evolution in dense environments

We present long-term numerical three-dimensional simulations of a relativistic outflow propagating through a galactic ambient medium and environment, up to distances $\sim 100$~kpc. Our aim is to study the role of dense media in the global dynamics of the radio source. We use a relativistic gas equation of state, and a basic description of thermal cooling terms. In previous work, we showed that a linear perturbation could enhance the jet propagation during the early phases of evolution, by introducing obliquity to the jet reverse shock. Here, we show that this effect is reduced in denser media. We find that the dentist-drill effect acts earlier, due to slower jet propagation and an increased growth of the helical instability. The global morphology of the jet is less elongated, with more prominent lobes. The fundamental physical parameters of the jet generated structure derived from our simulations fall within the estimated values derived for FRII jets in the 3C sample. In agreement with previous axisymmetric and three dimensional simulations in lower density media, we conclude that shock heating of the interstellar and intergalactic media is very efficient in the case of powerful, relativistic jets.

astro-ph.HE↗

arXiv2021

Jet propagation through inhomogeneous media and shock ionization

In this contribution we present the first numerical simulations of a relativistic outflow propagating through the inner hundreds of parsecs of its host galaxy, including atomic and ionised hydrogen, and the cooling effects of ionisation. Our results are preliminary, but we observe efficient shock ionization of atomic hydrogen in interstellar clouds. The mean density of the interstellar medium in these initial simulations is lower than that expected in typical galaxies, which makes cooling times longer and thus no recombination is observed inside the shocked region. The velocities achieved by the shocked gas in the simulations are in agreement with observational results, although with a wide spectrum of values.

astro-ph.HE↗

arXiv2021

Polarimetric properties of Event Horizon Telescope targets from ALMA

We present the results from a full polarization study carried out with ALMA during the first VLBI campaign, which was conducted in Apr 2017 in the $λ$3mm and $λ$1.3mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud AGN. We detect high linear polarization fractions (2-15%) and large rotation measures (RM $>10^{3.3}-10^{5.5}$ rad m$^{-2}$). For Sgr A* we report a mean RM of $(-4.2\pm0.3) \times10^5$ rad m$^{-2}$ at 1.3 mm, consistent with measurements over the past decade, and, for the first time, an RM of $(-2.1\pm0.1) \times10^5$ rad m$^{-2}$ at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at mm wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year time-scale, spanning the range from -1.2 to 0.3 $\times\,10^5$ rad m$^{-2}$ at 3 mm and -4.1 to 1.5 $\times\,10^5$ rad m$^{-2}$ at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT and ALMA. These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.

astro-ph.GA↗

arXiv2020

On the deceleration of Fanaroff-Riley Class I jets: mass loading of magnetized jets by stellar winds

In this paper we present steady-state RMHD simulations that include a mass-load term to study the process of jet deceleration. The mass-load mimics the injection of a proton-electron plasma from stellar winds within the host galaxy into initially pair plasma jets, with mean stellar mass-losses ranging from $10^{-14}$ to $10^{-9}\,{M_\odot\,yr^{-1}}$. The spatial jet evolution covers $\sim 500\,{\rm pc}$ from jet injection in the grid at 10~pc from the jet nozzle. Our simulations use a relativistic gas equation of state and a pressure profile for the ambient medium. We compare these simulations with previous dynamical simulations of relativistic, non-magnetised jets. Our results show that toroidal magnetic fields can prevent fast jet expansion and the subsequent embedding of further stars via magnetic tension. In this sense, magnetic fields avoid a runaway deceleration process. Furthermore, when the mass-load is large enough to increase the jet density and produce fast, differential jet expansion, the conversion of magnetic energy flux into kinetic energy flux (i.e., magnetic acceleration), helps to delay the deceleration process with respect to non-magnetised jets. We conclude that the typical stellar population in elliptical galaxies cannot explain jet deceleration in classical FRI radio galaxies. However, we observe a significant change in the jet composition, thermodynamical parameters and energy dissipation along its evolution, even for moderate values of the mass-load.

astro-ph.HE↗

arXiv2020

Triggering mixing and deceleration in FRI jets: a solution

Since Fanaroff & Riley (1974) reported the morphological and brightness dichotomy of radiogalaxies, and it became clear that the symmetric emission from jets and counter-jets in the centre-brightened, less powerful, FRI sources could be caused by jet deceleration, many works have addressed different mechanisms that could cause this difference. Recent observational results seem to indicate that the deceleration must be caused by the development of small-scale instabilities that force mixing at the jet boundary. According to these results, the mixing layer expands and propagates down to the jet axis along several kiloparsecs, until it covers the whole jet cross-section. Several candidate mechanisms have been proposed as the initial trigger for the generation of such mixing layer. However, the instabilities proposed so far do not fully manage to explain the observations of FRI jets and/or require a triggering mechanism. Therefore, there is not still a satisfactory explanation for the original cause of jet deceleration. In this letter, I show that the penetration (and exit) of stars from jets could give the adequate explanation by means of creating a jet-interstellar medium mixing layer that expands across the jet.

astro-ph.HE↗