arXiv subjects

J. M. Martí

Publications and source records attributed to J. M. Martí.

8 recordsLinked to original sources

arXiv2026

The impact of relativistic AGN jets on realistic galaxy cluster environments

Context. Low-power FRI-like radio jets dominate the AGN population, yet the main mechanism of heating the intracluster medium (ICM) and its efficiency remain a matter of debate. Aims. We investigate the impact of intermediate-power FRI-like relativistic jets on the inner region of realistic ICM, focusing on the role of weak shocks on heating and the environmental coupling in regulating energy deposition. Methods. We present six three-dimensional relativistic-hydrodynamic simulations of (1e44 - 1e45) erg/s FRI-like jets propagating through the central regions of realistic ICM environments extracted from cosmological GADGET-3 runs. Each simulation tracks 20 Myr of continuous jet activity with radiative cooling included. Results. Despite their intermediate power and mildly relativistic speed at injection, they decelerate rapidly to trans-sonic velocities (average Mach numbers ~ 2.3) and generate weak bow shocks that dominate the energy transfer. Approximately, 80% of the injected kinetic power is converted into internal energy of the ambient ICM, and bremsstrahlung cooling noticeably reduces the temperature of the shocked shells as they expand. Conclusions. Our results demonstrate that heating of the intergalactic and intracluster medium is highly efficient even in the case of weak shocks in FRI-like sources. This finding suggests low-power jets are a viable solution to the long-standing cooling-flow problem and likely regulate star formation across diverse galaxy cluster environments.

astro-ph.GA↗

arXiv2026

Stars as triggers of interstellar gas entrainment in relativistic jets

Low-power extragalactic jets are known to be decelerated and dissipate large amounts of energy within their host galaxies. However, the exact process by which this occurs is still elusive. The aim of this work is to probe the role of stars as triggers of jet mass-loading, deceleration and dissipation in Fanaroff-Riley type I radio galaxies. This is motivated by a theoretical model that proposes that stars interacting with the jet boundaries could facilitate entrainment of interstellar medium (ISM) gas into jets, favouring mixing and dissipation. We have performed a numerical experiment of stars entering a relativistic flow, using a relativistic hydrodynamics code. Our setup is limited to the interaction of three stars with the jet boundary, in order to assess the results in a limited, controlled, environment, although this number of stars may be plausible in the inner kpc-region of a massive galaxy. Our results allow us to estimate the amount of entrained ISM gas as the stars enter the jet. We show that the entrainment temporally induced on scales of tens of parsecs and thousands of years by evolved stars is comparable to the initial jet mass rate. The way in which this entrainment happens is by the creation of a low pressure region behind the stellar objects, which drags ambient gas into the jet flow. Our results confirm that stars interacting with the jet boundaries, and acting as catalysts of ISM/shear gas entrainment, can significantly contribute to jet mass-load and deceleration.

astro-ph.HE↗

arXiv2026

Stellar mass loading drives dissipation and reacceleration in AGN jets: Explaining VLBI-Gaia offsets and constraining jet power

Recent Very Long Baseline Interferometry (VLBI) and Gaia astrometry reveal systematic milliarcsecond-scale offsets between the radio and optical centroids of active galactic nuclei (AGN). These "radio-optical offsets" do not alter the standard opacity-driven interpretation of radio core shifts. Instead, they indicate that the optical emission centroid is frequently displaced downstream of the radio synchrotron optical depth $τ= 1$ surface, implying that additional dissipation and particle reacceleration occur beyond the opacity radio core within relativistic jets. We perform steady-state, axisymmetric relativistic magnetohydrodynamic (RMHD) simulations of AGN jets, including baryonic mass-load from stellar winds, varying jet kinetic power, and stellar core radius. Synthetic synchrotron emission maps in radio and optical bands are generated via a radiative transfer code, and centroid offsets are extracted for comparison with observations. Parsec-scale radio-optical offsets arise only for jet powers $L_{\rm j} \sim 10^{42.5} - 10^{44}\,\rm{erg}\,\rm{s}^{-1}$. In this regime, stellar winds trigger jet deceleration at intrinsic distances of a few $10^2-10^3\,\rm{pc}$, shifting the optical centroid downstream and producing offsets of $\sim 0.1 - 4\,\rm{mas}$ (a few tens of parsecs at $z=1$). Offsets depend on stellar distribution, viewing angle, and optical jet dominance, and vanish outside this power range. We reproduce the observed redshift evolution of offset incidence, linking it to the cosmic evolution of thermally pulsing asymptotic giant branch (TP-AGB) mass loss. Although stellar mass loading is unlikely to be the sole dissipation mechanism, its unavoidable presence in galactic nuclei makes it a natural baseline for energy dissipation. Radio-optical offsets therefore offer a constraint on AGN jet power and jet-host coupling, independent of traditional lobe-based methods.

astro-ph.HE↗

arXiv2025

Jet-red giant interactions as a source of extragalactic neutrinos: Insights from KM3-230213A

The production sites of high-energy astrophysical neutrinos remain uncertain, though growing evidence suggests a connection to relativistic jets in active galactic nuclei (AGN). We present a detailed analysis of the recent PeV neutrino event KM3-230213A reported by the KM3NeT collaboration, aiming to constrain the physical conditions of its source. Assuming proton acceleration at shocks, we derive the properties of the proton distribution and the energetics required to explain the neutrino emission. Using contemporaneous multiwavelength observations of three AGN flaring candidates within the error region, we examine the plausibility of each of them as the possible counterpart. Our results favor PMN J0606-0724, which exhibits a prominent radio flare coincident with the neutrino arrival. In this framework, the red-giant interaction remains the key driver of baryon injection and shock acceleration, while the dominant external photon field sets the neutrino energy scale: photospheric photons from the red giant yield ~1-10 PeV neutrinos, whereas the ~220 PeV event KM3-230213A is more naturally produced through interactions with colder infrared photons from the dusty torus.

astro-ph.HE↗

arXiv2025

Relativistic hydrodynamics simulations of supernova explosions within extragalactic jets

Jets in active galactic nuclei have to cross significant distances within their host galaxies, meeting large numbers of stars of different masses and evolution stages in their paths. Given enough time, supernova explosions within the jet will eventually happen, and may have a strong impact on its dynamics, potentially triggering powerful non-thermal activity. We carried out a detailed numerical study to explore the dynamics of the interaction between the ejecta of a supernova explosion and a relativistic extragalactic jet. By means of relativistic hydrodynamics simulations using the code RATPENAT, we simulated the jet-ejecta interaction in two different geometries or scenarios: a two-dimensional, axisymmetric simulation, and a three-dimensional one, which includes the orbital velocity of the exploding star. Although initially filling a region much smaller than the jet radius, the ejecta expands and eventually covers most of the jet cross section. The expansion is enhanced as more energy from the jet is converted into kinetic and internal energy of the ejecta, which also favors the ejecta disruption, all this occurring on timescales ~ 10^4 yr. Although a complete numerical convergence of the results is unattainable given the subsonic, turbulent nature of the interaction region, the simulations are consistent in their description of the gross morphological and dynamical properties of the interaction process. At the end of the simulations, the supernova ejecta has already partially mixed with the relativistic jet. The results also suggest that the jet-ejecta interaction may be a non-negligible non-thermal emitter. Moreover, due to efficient mixing, the interaction region can be a potential source of ultra-high-energy cosmic rays of heavy composition.

astro-ph.HE↗

arXiv2023

Magnetic and thermal acceleration in extragalactic jets: An application to NGC 315

Aims. Relativistic jets launched from active galactic nuclei accelerate up to highly relativistic velocities within a few parsecs to tens of parsecs. The precise way in which this process takes place is still under study. While magnetic acceleration is known to be able to accelerate relativistic outflows, little attention has been paid to the role of thermal acceleration. The latter has been assumed to act only on compact regions, very close to the central engine, and to become negligible on parsec scales. However, this holds under the assumption of small internal energies as compared to the magnetic ones, and whether this is true or what happens when we drop this assumption is currently uncertain. Methods. We use a 2D relativistic magnetohydrodynamical code to explore jet acceleration from sub-parsec to parsec scales. As initial conditions for our models, we use observational constraints on jet properties derived by means of very long baseline interferometry observations for a Fanaroff Riley I radio galaxy, NGC\,315. We investigate the parameter space established for this source and perform a number of simulations of magnetically, thermally or kinetically dominated jets at injection, and compare our results with the observed ones. Results. Our simulated jets show that when thermal energy is comparable to or exceeds magnetic energy, thermal acceleration becomes significant at parsec scales. This result has important consequences, potentially extending the acceleration region far beyond the collimation scales, as thermal acceleration can effectively operate within a conically expanding jet. In all the models, we observe acceleration to be driven by expansion, as expected. A number of our models allow us to reproduce the acceleration and opening angles observed in NGC\,315. Finally, our results indicate that disk-launched winds might play an important role in the jet propagation.

astro-ph.HE↗

arXiv2022

3D RMHD simulations of jet-wind interactions in High Mass X-ray Binaries

The interaction of jets in High-Mass X-ray Binaries (HMXBs) with the strong winds driven by the hot companion star in the vicinity of the compact object is fundamental to understand the jet dynamics, non-thermal emission and long-term stability. However, the role of the jet magnetic field in this process is unclear. We study the dynamical role of weak and moderate-to-strong toroidal magnetic fields during the first hundreds of seconds of jet propagation, focusing on the magnetized flow dynamics and the mechanisms of energy conversion. We have developed the code Lóstrego v1.0, a new 3D RMHD code to simulate astrophysical plasmas in Cartesian coordinates. Using this tool, we performed the first 3D RMHD numerical simulations of relativistic magnetized jets propagating through the clumpy stellar wind in a HMXB. The overall morphology and dynamics of weakly magnetized jet models is similar to previous hydrodynamical simulations, where the jet head generates a strong shock in the ambient medium and the initial over-pressure with respect to the stellar wind drives one or more recollimation shocks. In the time scales of our simulations, these jets are ballistic and seem to be more stable against internal instabilities than jets with the same power in the absence of fields. However, moderate-to-strong toroidal magnetic fields favour the development of current-driven instabilities and the disruption of the jet within the binary. A detailed analysis of the energy distribution in the relativistic outflow and the ambient medium reveals that both magnetic and internal energies can contribute to the effective acceleration of the jet. We certify that the jet feedback into the ambient medium is highly dependent on the jet energy distribution at injection, where hotter, more dilute and/or more magnetized jets are more efficient, as anticipated by feedback studies in the case of jets in active galaxies.

astro-ph.HE↗

arXiv2010

A Roe-type Riemann solver based on the spectral decomposition of the equations of Relativistic Magnetohydrodynamics

In a recent paper (Antón et al. 2010) we have derived sets of right and left eigenvectors of the Jacobians of the relativistic MHD equations, which are regular and span a complete basis in any physical state including degenerate ones. We present a summary of the main steps followed in the above derivation and the numerical experiments carried out with the linearized (Roe-type) Riemann solver we have developed, and some note on the (non-)convex character of the relativistic MHD equations.

astro-ph.HE↗