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In gamma-ray bursts (GRBs), ∼100–1000 s after the prompt emission, afterglow observations have consistently shown X-ray excesses detected in the form of flares (in long GRBs) or extended emission (in short GRBs). These observations are interpreted as emissions from jets launched by late central engine activity. However, the characteristics of these late-time jets, particularly the dissipation radius (r diss), Lorentz factor (Γ), and cosmic-ray loading factor (ξ p ), remain unknown despite their importance. Here, in order to understand the properties of the late-time jets with future multimessenger observations, we estimate the detectability of neutrinos associated with late-time emissions for a wide range of r diss and Γ, assuming ξ p = 10. We take into account external seed photons from the cocoon around the jets, which can enhance the neutrino production through photohadronic interaction in the jet dissipation region. Our results are still consistent with the upper limit obtained by IceCube. Our calculations indicate a promising prospect for neutrino detection with IceCube-Gen2 through the stacking of ∼1000–2000 events, for a wide range of r diss and Γ. We found that setting an optimal energy threshold of 10 TeV can significantly reduce noise without negatively affecting neutrino detection. Furthermore, even in the case of nondetection, we show that meaningful constraints on the characteristics of the late-time jets can be obtained. [ABSTRACT FROM AUTHOR]

AT 2022cmc is a recently documented tidal disruption event that exhibits a luminous jet, accompanied by fast-declining X-ray and long-lasting radio and millimeter emission. Motivated by the distinct spectral and temporal signatures between the X-ray and radio observations, we propose a multizone model involving relativistic jets with different Lorentz factors. We systematically study the evolution of faster and slower jets in an external density profile, considering the continuous energy injection rate associated with time-dependent accretion rates before and after the mass fallback time. We investigate time-dependent multiwavelength emission from both the forward shock (FS) and reverse shock (RS) regions of the fast and slow jets, in a self-consistent manner. Our analysis demonstrates that the energy injection rate can significantly impact the jet evolution and subsequently influence the lightcurves. We find that the X-ray spectra and lightcurves could be described by electron synchrotron emission from the RS of the faster jet, in which the late-time X-ray upper limits, extending to 400 days after the disruption, could be interpreted as a jet break. Meanwhile, the radio observations can be interpreted as a result of synchrotron emission from the FS region of the slower jet. We also discuss prospects for testing the model with current and future observations. [ABSTRACT FROM AUTHOR]

The tidal disruption event (TDE) AT2022cmc represents the fourth known example of a relativistic jet produced by the tidal disruption of a stray star, providing a unique probe of the formation and evolution of relativistic jets in otherwise dormant supermassive black holes (SMBHs). Here we present deep, late-time Chandra observations of AT2022cmc extending to t obs ≈ 400 days after disruption. Our observations reveal a sudden decrease in the X-ray brightness by a factor of ≳14 over a factor of ≈2.3 in time, and a deviation from the earlier power-law decline with a steepening α ≳ 3.2 (F X ∝ t − α ), steeper than expected for a jet break, and pointing to the cessation of jet activity at t obs ≈ 215 days. Such a transition has been observed in two previous TDEs (Swift J1644+57 and Swift J2058+05). From the X-ray luminosity and the timescale of jet shut-off, we parameterize the mass of the SMBH in terms of unknown jet efficiency and accreted mass fraction parameters. Motivated by the disk–jet connection in active galactic nuclei, we favor black hole masses ≲105 M ⊙ (where the jet and disk luminosities are comparable), and disfavor larger black holes (in which extremely powerful jets are required to outshine their accretion disks). We additionally estimate a total accreted mass of ≈0.1 M ⊙. Applying the same formalism to Swift J1644+57 and Swift J2058+05, we favor comparable black hole masses for these TDEs of ≲ a few × 105 M ⊙, and suggest that jetted TDEs may preferentially form from lower-mass black holes when compared to nonrelativistic events, owing to generally lower jet and higher disk efficiencies at higher black hole masses. [ABSTRACT FROM AUTHOR]

Relativistic discrete ejecta launched by black hole X-ray binaries (BH XRBs) can be observed to propagate up to parsec-scales from the central object. Observing the final deceleration phase of these jets is crucial to estimate their physical parameters and to reconstruct their full trajectory, with implications for the jet powering mechanism, composition, and formation. In this paper, we present the results of the modelling of the motion of the ejecta from three BH XRBs: MAXI J1820 |$+$| 070, MAXI J1535–571, and XTE J1752–223, for which high-resolution radio and X-ray observations of jets propagating up to |$\sim$| 15 arcsec (⁠|$\sim$| 0.6 pc at 3 kpc) from the core have been published in the recent years. For each jet, we modelled its entire motion with a dynamical blast-wave model, inferring robust values for the jet Lorentz factor, inclination angle and ejection time. Under several assumptions associated to the ejection duration, the jet opening angle and the available accretion power, we are able to derive stringent constraints on the maximum jet kinetic energy for each source (between |$10^{43}$| and |$10^{44}$| erg, including also H1743–322), as well as placing interesting upper limits on the density of the ISM through which the jets are propagating (from |$n_{\rm ISM} \lesssim 0.4$| cm |$^{-3}$| down to |$n_{\rm ISM} \lesssim 10^{-4}$| cm |$^{-3}$|⁠). Overall, our results highlight the potential of applying models derived from gamma-ray bursts to the physics of jets from BH XRBs and support the emerging picture of these sources as preferentially embedded in low-density environments. [ABSTRACT FROM AUTHOR]

Context. Relativistic magnetic reconnection studies have so far focused on symmetric configurations, where the upstream plasma has identical properties on the two sides of the layer. Yet, just like nonrelativistic reconnection on the dayside of the Earth's magnetosphere, relativistic reconnection can also operate at the interface between highly asymmetric environments. The boundary layer between a relativistic jet and an accretion flow forming around a supermassive black hole can present asymmetric configurations in terms of plasma composition, bulk velocity, temperature, and magnetization. Aims. We conducted the first study of relativistic magnetic reconnection where the upstream plasma is composed of electron-positron pairs on one side, and electrons and ions on the other. We also investigated the impact of a relativistic symmetric shear flow applied along the reconnecting field lines. Methods. We simulated magnetic reconnection using 2D particle-in-cell simulations. The initial setup was adapted from a classic Harris layer without a guide field, modified to accommodate plasma-composition and shear asymmetries in the upstream medium. Results. For a composition-asymmetric setup, we find that the reconnection dynamics is driven by the electron-ion side, which is the plasma with the lowest magnetization. The energy partition favors accelerating ions at the expense of electrons even more than in a corresponding symmetric setup. With respect to shear, a super-Alfvénic upstream decreases the laboratory-frame reconnection rate, but, unlike in nonrelativistic studies, does not shut off reconnection completely. Conclusions. The asymmetries examined in this work lower the overall efficiency of electron acceleration relative to corresponding symmetric configurations. In the context of a black hole jet-disk boundary, asymmetric reconnection alone is probably not efficient at accelerating electrons to very high energies, but it might facilitate plasma mixing and particle injection for other acceleration channels at the interface. [ABSTRACT FROM AUTHOR]

A fraction of the active supermassive black holes at the centers of galaxies in our Universe are capable of launching extreme kiloparsec-long relativistic jets. These jets are known multiband (radio to γ-ray) and multimessenger (neutrino) emitters, and some of them have been monitored over decades at all accessible wavelengths. However, several open questions remain unanswered about the processes powering these highly energetic phenomena. These jets intrinsically produce soft-to-hard X-ray emission that extends from E > 0.1 keV up to E > 100 keV, and simultaneous broadband X-ray coverage, combined with excellent timing and imaging capabilities, is required to uncover the physics of jets. Indeed, truly simultaneous soft-to-hard X-ray coverage, in synergy with current and upcoming high-energy facilities (such as IXPE, COSI, CTAO, etc.) and neutrino detectors (e.g., IceCube), would enable us to disentangle the particle population responsible for the high-energy radiation from these jets. A sensitive hard X-ray survey (F20-80 keV < 10-15erg cm-2 s-1) could unveil the bulk of their population in the early Universe. Acceleration and radiative processes responsible for the majority of their X-ray emission would be pinned down by microsecond timing capabilities at both soft and hard X-rays. Furthermore, imaging jet structures for the first time in the hard X-ray regime could unravel the origin of their high-energy emission. The proposed Probe-class mission concept High Energy X-ray Probe (HEX-P) combines all these required capabilities, making it the crucial next-generation X-ray telescope in the multi-messenger, time-domain era. HEX-P will be the ideal mission to unravel the science behind the most powerful accelerators in the Universe. [ABSTRACT FROM AUTHOR]

We investigate impacts of stellar rotation and magnetic fields on black hole (BH) formation and its subsequent explosive activities, by conducting axisymmetric radiation-magnetohydrodynamics simulations of gravitational collapse of a 70  |$\mathrm{M}_\odot$| star with two-moment multi energy neutrino transport in full general relativity for the first time. Due to its dense stellar structure, all models cannot avoid the eventual BH formation even though a strongly magnetized model experiences the so-called magnetorotational explosion prior to the BH formation. One intriguing phenomenon observed in the strongly magnetized model is the formation of a relativistic jet in the post-BH formation. The relativistic jet is the outcome of a combination of strong magnetic fields and low-density materials above the BH. The jet further enhances the explosion energy beyond |$\sim 10^{52}$|  erg, which is well exceeding the gravitational overburden ahead of the shock. Our self-consistent supernova models demonstrate that rotating magnetized massive stars at the high-mass end of supernova progenitors could be a potential candidate of hypernova and long gamma-ray burst progenitors. [ABSTRACT FROM AUTHOR]

A tight correlation between the radio and X-ray emission in the hard state of black hole X-ray binaries (BHXRBs) indicates an intrinsic disc–jet connection in stellar black hole (BH) accretion systems, though the detailed physics processes at work are still quite unclear. A hot accretion flow is suggested to match the outer cold thin disc at a certain radius in the hard state, which may vary with the accretion rate. In this work, we assume that the magnetic field generated in the outer thin disc is advected inwards by the inner hot accretion flow, which is substantially enhanced near the BH. Such a strong field threading the horizon of a spinning BH is responsible for launching relativistic jets in BHXRBs via the Blandford–Znajek mechanism. Thus, both the jet power and the X-ray emission increase with the mass accretion rate, and we find that our model calculations are able to reproduce the observed radio/X-ray correlation quantitatively. For some individual BHXRBs, the slopes of the radio/X-ray correlations become steeper when the sources are brighter. Our model calculations show that this feature is due to the transition of the outer disc from gas pressure dominated to radiation pressure dominated, which leads to different accretion rate dependence of the field strength in the outer disc. [ABSTRACT FROM AUTHOR]

We present analyses of Suzaku XIS light curves and spectra of the BL Lac object OJ 287 with observations positioned primarily around proposed recurrent optical outbursts. The first two observations were performed in 2007 April 10–13 (epoch 1) and 2007 November 7–9 (epoch 2) that, respectively, correspond to a low and a high optical state and which, within the binary supermassive black hole model for OJ 287, precede and follow the impact flare. The last three observations, made consecutively during 2015 May 3–9 (epoch 3), were during the post-impact state of the 2013 disc impact and are the longest continuous X-ray observation of OJ 287 taken before the optical outburst in 2015 December. Intraday variability is found in both the soft (0.5–2 keV) and hard (2–10 keV) bands. The discrete correction function analysis of the light curves in both bands peaks at zero lag during epochs 2 and 3, indicating that the emission in both bands was cospatial and emitted from the same population of leptons. Power spectral densities of all three light curves are red noise dominated, with a rather wide range of power spectrum slopes. These X-ray spectra are overall consistent with power laws but with significantly different spectral indices. In the 2015 observations the X-ray spectrum softens during the flare, showing an obvious soft X-ray excess that was not evident in the 2007 observations. We discuss the implications of these observations on the jet, the possible accretion disc, and the binary supermassive black hole model proposed for the nearly periodic optical flaring of OJ 287. [ABSTRACT FROM AUTHOR]

We report on the discovery of one of the most extreme cases of high-frequency radio variability ever measured in active galactic nuclei (AGNs), observed on time-scales of days and exhibiting variability amplitudes of 3–4 orders of magnitude. These sources, all radio-weak narrow-line Seyfert 1 (NLS1) galaxies, were discovered some years ago at Aalto University Metsähovi Radio Observatory (MRO) based on recurring flaring at 37 GHz, strongly indicating the presence of relativistic jets. In subsequent observations with the Karl G. Jansky Very Large Array (JVLA) at 1.6, 5.2, and 9.0 GHz no signs of jets were seen. To determine the cause of their extraordinary behaviour, we observed them with the JVLA at 10, 15, 22, 33, and 45 GHz, and with the Very Long Baseline Array (VLBA) at 15 GHz. These observations were complemented with single-dish monitoring at 37 GHz at MRO, and at 15 GHz at Owens Valley Radio Observatory (OVRO). Intriguingly, all but one source either have a steep radio spectrum up to 45 GHz, or were not detected at all. Based on the 37 GHz data, the time-scales of the radio flares are a few days, and the derived variability brightness temperatures and variability Doppler factors are comparable to those seen in blazars. We discuss alternative explanations for their extreme behaviour, but so far no definite conclusions can be made. These sources exhibit radio variability at a level rarely, if ever, seen in AGN. They might represent a new type of jetted AGN, or a new variability phenomenon, and thus deserve our continued attention. [ABSTRACT FROM AUTHOR]

The gamma-ray emitting narrow-line Seyfert 1 galaxies are a unique class of objects that launch powerful jets from relatively lower-mass black hole systems compared to the Blazars. However, the black hole masses estimated from the total flux spectrum suffer from the projection effect, making the mass measurement highly uncertain. The polarized spectrum provides a unique view of the central engine through scattered light. We performed spectropolarimetric observations of the gamma-ray emitting narrow-line Seyfert 1 galaxy 1H0323 + 342 using SPOL/MMT. The degree of polarization and polarization angle are 0.122 |$\pm$| 0.040 per cent and 142 |$\pm$| 9 degrees, while the H |$\alpha$| line is polarized at 0.265 |$\pm$| 0.280 per cent. We decomposed the total flux spectrum and estimated broad H |$\alpha$| full width at half maximum of 1015 km s |$^{-1}$| . The polarized flux spectrum shows a broadening similar to the total flux spectrum, with a broadening ratio of 1.22. The Monte Carlo radiative transfer code 'STOKES' applied to the data provides the best fit for a small viewing angle of 9–24 deg and a small optical depth ratio between the polar and the equatorial scatters. A thick broad-line region with significant scale height can explain a similar broadening of the polarized spectrum compared to the total flux spectrum with a small viewing angle. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of 30 ks Chandra and 46.8 ks (13 h) 1.4 GHz GMRT radio data on the cool-core cluster RXCJ0352.9 + 1941 to investigate AGN activities at its core. This study confirms a pair of X-ray cavities at projected distances of about 10.30 and 20.80 kpc, respectively, on the NW and SE of the X-ray peak. GMRT L band (1.4 GHz) data revealed a bright radio source associated with the core of this cluster hosting multiple jet-like emissions. The spatial association of the X-ray cavities with the inner pair of radio jets confirms their origin due to AGN outbursts. The 1.4 GHz radio power 7.4 ± 0.8 × 10 39 erg s - 1 is correlated with the mechanical power stored in the X-ray cavities ( ∼ 7.90 × 10 44 erg s - 1 ), implying that the power injected by radio jets in the ICM is sufficient enough to offset the radiative losses. The X-shaped morphology of diffuse radio emission seems to be comprised of two pairs of orthogonal radio jets, likely formed due to a spin-flip of jets due to the merger of two systems. The X-ray surface brightness analysis of the ICM in its environment revealed two non-uniform, extended spiral-like emission structures on either side of the core, pointing towards gas sloshing due to a minor merger. It might have resulted in a cold front at ∼ 31 arcsec (62 kpc) with a temperature jump of 1.44 keV. [ABSTRACT FROM AUTHOR]

In the absence of supplementary heat, the radiative cooling of halo gas around massive galaxies (Milky Way mass and above) leads to an excess of cold gas or stars beyond observed levels. Active galactic nucleus jet-induced heating is likely essential, but the specific properties of the jets remain unclear. Our previous work concludes from simulations of a halo with |$10^{14} \,\mathrm{ M}_\odot$| that a successful jet model should have an energy flux comparable to the free-fall energy flux at the cooling radius and should inflate a sufficiently wide cocoon with a long enough cooling time. In this paper, we investigate three jet modes with constant fluxes satisfying the criteria, including high-temperature thermal jets, cosmic ray (CR)-dominant jets, and widely precessing kinetic jets in |$10^{12}-10^{15}\, {\rm M}_{\odot }$| haloes using high-resolution, non-cosmological magnetohydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, conduction, and viscosity. We find that scaling the jet energy according to the free-fall energy at the cooling radius can successfully suppress the cooling flows and quench galaxies without violating observational constraints. On the contrary, if we scale the energy flux based on the total cooling rate within the cooling radius, strong interstellar medium cooling dominates this scaling, resulting in a jet flux exceeding what is needed. Among the three jet types, the CR-dominant jet is most effective in suppressing cooling flows across all surveyed halo masses due to enhanced CR pressure support. We confirm that the criteria for a successful jet model work across a wider range, encompassing halo masses of |$10^{12}-10^{15} {\rm M_\odot }$|⁠. [ABSTRACT FROM AUTHOR]

We have investigated whether the lack of X-ray pulsations from most neutron star (NS) low-mass X-ray binaries (LMXBs) could be due to the extension of their inner disc to the NS surface. To estimate the inner disc radii, we have employed the model, recently proposed to account for the torque reversals of LMXBs. In this model, the inner disc radius depends on the spin period as well as the dipole moment and the mass inflow rate of the disc. Our model results indicate that most LMXBs have mass accretion rates above the minimum critical rates required for the inner disc to reach down to the NS surface and thereby quench the pulsed X-ray emission. For most sources X-ray pulsations are allowed when the period decreases below a certain critical value. For the same parameters, the model is also consistent with the observed X-ray luminosity ranges of the individual accreting millisecond X-ray pulsars (AMXPs). The paucity of AMXPs compared to the majority population of non-pulsing LMXBs is explained, as well as the fact that AMXPs are transient sources. [ABSTRACT FROM AUTHOR]

In this work, we present the results of a detailed X-ray spectral analysis of the brightest active galactic nuclei (AGNs) detected in the XMM–Newton 1.75 Ms Ultra Narrow Deep Field. We analysed 23 AGNs that have a luminosity range of |$\sim 10^{42} {\!-\!} 10^{46}\, \rm {erg}\, \rm {s}^{-1}$| in the |$2 {\!-\!} 10\, \rm {keV}$| energy band, redshifts up to 2.66, and |$\sim 10\,000$| X-ray photon counts in the |$0.3{ \!-\! }10\, \rm {keV}$| energy band. Our analysis confirms the 'Iwasawa – Taniguchi effect,' an anticorrelation between the X-ray luminosity (⁠|$L_x$|⁠) and the Fe – k |$\alpha$| equivalent width (⁠|${\rm EW}_{\rm Fe}$|⁠) possibly associated with the decreasing of the torus covering factor as the AGN luminosity increases. We investigated the relationship among black hole mass (⁠|$M_{\rm BH}$|⁠), |$L_x$|⁠ , and X-ray variability, quantified by the Normalized Excess Variance (⁠|$\sigma ^2_{\rm rms}$|⁠). Our analysis suggest an anticorrelation in both |$M_{\rm BH} - \sigma ^2_{\rm rms}$| and |$L_x- \sigma ^2_{\rm rms}$| relations. The first is described as |$\sigma ^2_{\rm rms} \propto M^{-0.26 \pm 0.05}_{\rm BH}$|⁠ , while the second presents a similar trend with |$\sigma ^2_{\rm rms} \propto L_{x}^{-0.31 \pm 0.04}$|⁠. These results support the idea that the luminosity – variability anticorrelation is a byproduct of an intrinsic relationship between the BH mass and the X-ray variability, through the size of the emitting region. Finally, we found a strong correlation among the Eddington ratio (⁠|$\lambda _{\rm Edd}$|⁠), the hard X-ray photon index (⁠|$\Gamma$|⁠), and the illumination factor |$\log (A)$|⁠ , which is related to the ratio between the number of Compton scattered photons and the number of seed photons. The |$\log (\lambda _{\rm Edd})-\Gamma -\log (A)$| plane could arise naturally from the connection between the accretion flow and the hot corona. [ABSTRACT FROM AUTHOR]

Jets from active nuclei may supply the heating which moderates cooling and accretion from the circum-galactic medium. While steady overpressured jets can drive a circulatory flow, lateral energy transfer rarely exceeds 3 per cent of jet power, after the initial bow shock has advanced. Here, we explore if pulses in high-pressure jets are capable of sufficient lateral energy transfer into the surrounding environment. We answer this by performing a systematic survey of numerical simulations in an axisymmetric hydrodynamic mode. Velocity pulses along low Mach jets are studied at various overpressures. We consider combinations of jet velocity pulse amplitude and frequency. We find three flow types corresponding to slow, intermediate, and fast pulsations. Rapid pulsations in light jets generate a series of travelling shocks in the jet. They also create ripples which propagate into the ambient medium while a slow convection flow brings in ambient gas which is expelled along the jet direction. Long period pulses produce slowly evolving patterns which have little external effect, while screeching persists as in non-pulsed jets. In addition, rapid pulses in jets denser than the ambient medium generate a novel breathing cavity analogous to a lung. Intermediate period pulses generate a series of bows via a bellows action which transfer energy into the ambient gas, reaching power efficiencies of over 30 per cent when the jet overpressure is sufficiently large. This may adequately inhibit galaxy gas accretion. In addition, such pulses enhance the axial out-flow of jet material, potentially polluting the circum-galactic gas with metal-enriched interstellar gas. [ABSTRACT FROM AUTHOR]

We conduct three-dimensional hydrodynamic simulations, and show that when a secondary star launches jets while interacting with a primary |$0.88~\mathrm{ M}_{\rm \odot }$| giant star in a close orbit, the system can avoid entering the common envelope evolution (CEE). Instead of a fast in-spiral, the companion slowly enters the envelope as the jets facilitate the unbinding of the giant star envelope outside the companion orbit, in what is termed the grazing envelope evolution (GEE). The assumptions are that the secondary main-sequence star accretes mass via an accretion disc, and that the accretion disc launches the jets. We perform two sets of simulations with and without jets for different companion masses at the range of 0.1–0.9 M |$_{\odot }$|⁠ , maintaining a constant jet power in the former case of |$1.5\times 10^{38}~{\rm ergs~s^{-1}}$|⁠. We examine which of the simulated systems undergo a GEE rather than a CEE and how efficiently the jets unbind the envelope. The results indicate that systems with companion masses at the range of 0.1–0.3 M |$_{\odot }$| are more likely to result in a phase of GEE lasting 1–3 yr. With the smallest companion, a 0.1 solar mass star, the jets unbind 65 per cent of the envelope mass, while almost none of the envelope is unbound if jets are not present. The results of the simulations show that the GEE can serve as an alternative to the CEE, in forming short-period binaries that have compact objects and an ejected envelope. [ABSTRACT FROM AUTHOR]

Supermassive black hole binaries (SMBHBs) are natural by-products of galaxy mergers and are expected to be powerful multimessenger sources. They can be powered by the accretion of matter and then radiate across the electromagnetic spectrum, much like normal active galactic nuclei (AGNs). Current electromagnetic observatories have a good chance of detecting and identifying these systems in the near future. However, precise observational indicators are needed to distinguish individual AGNs from SMBHBs. In this paper, we propose a novel electromagnetic signature from SMBHBs: non-thermal emission produced by the interaction between the jets ejected by the black holes. We study close SMBHBs, which accrete matter from a circumbinary disc and the mini-discs formed around each hole. Each black hole ejects a magnetically dominated jet in the direction of its spin through the Blandford–Znajek mechanism. We argue that in such a situation, the interaction between the jets can trigger strong magnetic reconnection events, where particles are accelerated and emit non-thermal radiation. Depending on whether the jets are aligned or misaligned, this radiation can have different periodicities. We model the evolution of the particles accelerated during the dual jet interaction and calculate their radiative output, obtaining spectra and providing estimates for the variability time-scales. We finally discuss how this emission compares with that of normal AGNs. [ABSTRACT FROM AUTHOR]

The nearby ultraluminous infrared galaxy (ULIRG) IRAS F01004−2237 exhibits 100 kpc scale continuum emission at radio wavelengths. The absence of extended X-ray emission in IRAS F01004−2237 has suggested an active galactic nucleus (AGN) origin for the extended radio emission, whose properties and role in merging systems still need to be better understood. We present the results of multifrequency observations of IRAS F01004−2237 conducted by the Very Long Baseline Array at 2.3 and 8.4 GHz. Compact 8.4 GHz continuum emission was detected on a 1 pc scale in the nuclear region with an intrinsic brightness temperature of 108.1 K suggesting that the radio source originated from an AGN, potentially driving the extended emission. In contrast, no significant emission was observed at 2.3 GHz, indicating the presence of low-frequency absorption. This absorption cannot be attributed solely to synchrotron self-absorption; alternatively, free–free absorption due to thermal plasma is mainly at work in the spectrum. From combined perspectives, including mid-infrared and X-ray data, the AGN is obscured in a dense environment. The kinetic power of the nonthermal jet, as inferred from the extended emission, can play a more important role in dispersing the surrounding medium than the thermal outflow in IRAS F01004−2237. These findings hint that jet activities in ULIRGs may contribute to AGN feedback during galaxy evolution induced by merger events. [ABSTRACT FROM AUTHOR]

We present a multi-wavelength analysis, from the radio to the X-ray band, of the redshift z = 6.44 VIK J2318−31 radio-loud quasi-stellar object, one of the most distant currently known of this class. The work is based on newly obtained observations (uGMRT, ATCA, and Chandra) as well as dedicated archival observations that have not yet been published (GNIRS and X-shooter). Based on the observed X-ray and radio emission, its relativistic jets are likely young and misaligned from our line of sight. Moreover, we can confirm, with simultaneous observations, the presence of a turnover in the radio spectrum at νpeak ∼ 650 MHz that is unlikely to be associated with self-synchrotron absorption. From the near-infrared spectrum we derived the mass of the central black hole, $ M_{\mathrm{BH}}=8.1^{+6.8}_{-5.6} \times 10^8\,{M_{\odot}} $ , and the Eddington ratio, $ \lambda_{\mathrm{EDD}} = 0.8^{+0.8}_{-0.6} $ , using broad emission lines as well as an accretion disc model fit to the continuum emission. Given the high accretion rate, the presence of a ∼8 × 108 M⊙ black hole at z = 6.44 can be explained by a seed black hole (∼104 M⊙) that formed at z ∼ 25, assuming a radiative efficiency ηd ∼ 0.1. However, by assuming ηd ∼ 0.3, as expected for jetted systems, the mass observed would challenge current theoretical models of black hole formation. [ABSTRACT FROM AUTHOR]

We present rest-frame optical JWST Near-infrared Spectrograph (NIRSpec) integral field unit (IFU) spectroscopy of TN J1338−1942 at z  = 4.1, one of the most luminous galaxies in the early universe with powerful extended radio jets. Previous observations showed evidence for strong, large-scale outflows based on its large (∼150 kpc) halo detected in Ly α, and high-velocity [O  ii ] emission features detected in ground-based spectroscopy. Our NIRSpec/IFU observations spatially resolve the emission line properties across the host galaxy. We find at least five concentrations of strong line emission, coinciding with discrete continuum features previously detected in imaging from Hubble Space Telescope and JWST , over an extent of ∼2 arcsec (∼15 kpc). The spectral diagnostics unambiguously trace active galactic nuclei (AGN) activity plus interaction between the interstellar medium and the radio jet as the dominant mechanisms for the ionization state and kinematics of the gas in the system. A secondary region of very high ionization lies at roughly 5 kpc away from the nucleus, and within the context of an expanding cocoon enveloping the radio lobe, this may be explained by strong shock-ionization of the entrained gas. However, it could also signal the presence of a second obscured AGN, which may offer an explanation for an intriguing outflow feature seen perpendicular to the radio axis. The presence of a dual supermassive black holes system in this galaxy would support that large galaxies in the early Universe quickly accumulated their mass through the merging of smaller units, at the centres of large overdensities. The inferred black hole mass to stellar mass ratio of 0.01−0.1 for TNJ1338 points to a more rapid assembly of black holes compared to the stellar mass of galaxies at high redshifts, consistent with other recent observations. [ABSTRACT FROM AUTHOR]

In this study, a model for light travel time effects for emission from a plasma blob in a blazar jet is presented. This calculation could be incorporated into more complex models with particle acceleration and radiation mechanisms, but as presented here, it is agnostic to these mechanisms. This model includes light travel time effects for an expanding or contracting blob. As examples, this model is applied to a flare observed by VERITAS and MAGIC from Mrk 421 in 2013 and a flare observed by the Fermi Large Area Telescope from 3C 454.3 in 2010. [ABSTRACT FROM AUTHOR]

The merger of two magnetized compact objects, such as neutron stars, forms a compact object which may launch a relativistic and collimated jet. Numerical simulations of the process show that a dense and highly magnetized medium surrounds the system. This study presents a semi-analytical model that models the effects that a static magnetized medium with a tangled field produces in relativistic, collimated, and non-magnetized jets. The model is a first approximation that addresses the magnetic field present in the medium and is based on pressure equilibrium principles between the jet, cocoon, and external medium. A fraction of the ambient medium field is allowed to be entrained in the cocoon. We find that the jet and cocoon properties may be affected by high magnetic fields (≳ 1015 G) and mixing. The evolution of the system may vary up to |$\sim 10{{\ \rm per\ cent}}$| (compared to the non-magnetized case). Low-mixing may produce a slower broader jet with a broader and more energetic cocoon would be produced. On the other hand, high-mixing could produce a faster narrower jet with a narrow and less-energetic cocoon. Two-dimensional hydrodynamical simulations are used to validate the model and to constrain the mixing parameter. Although the magnetic field and mixing have a limited effect, our semi-analytic model captures the general trend consistent with numerical results. For high magnetization, the results were found to be more consistent with the low mixing case in our semi-analytic model. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGNs) play an integral role in galaxy formation and evolution by influencing galaxies and their environments through radio jet feedback. Historically, interpreting observations of radio galaxies and quantifying radio jet feedback has been challenging due to degeneracies between their physical parameters. In particular, it is well established that different combinations of jet kinetic power and environment density can yield indistinguishable radio continuum properties, including apparent size and Stokes I luminosity. We present an approach to breaking this degeneracy by probing the line-of-sight environment with Faraday rotation. We study this effect in simulations of three-dimensional relativistic magnetohydrodynamic AGN jets in idealized environments with turbulent magnetic fields. We generate synthetic Stokes I emission and Faraday rotation measure (RM) maps, which enable us to distinguish between our simulated sources. We find enhanced RMs near the jet head and lobe edges. We show that increasing the environment density and the average cluster magnetic field strength broadens the distribution of Faraday rotation measure values. We study the depolarization properties of our sources, finding that the hotspot regions depolarize at lower frequencies than the lobes. We quantify the effect of depolarization on the RM distribution, finding that the frequency at which the source is too depolarized to measure the RM distribution accurately is a probe of environmental properties. This technique offers a range of new opportunities for upcoming surveys, including probing radio galaxy environments and determining more accurate estimates of the AGN feedback budget. [ABSTRACT FROM AUTHOR]

Strong AGN heating provides an alternative means for the disruption of cluster cool cores (CCs) to cluster mergers. In this work, we present a systematic Chandra study of a sample of 108 nearby (z < 0.1) galaxy clusters, to investigate the effect of AGN heating on CCs. About 40 per cent of clusters with small offsets between the BCG and the X-ray centre (≤50 kpc) have small CCs. For comparison, 14 of 17 clusters with large offsets have small CCs, which suggests that mergers or sloshing can be efficient in reducing the CC size. Relaxed, small CC clusters generally have weak radio AGNs (⁠|$P_{1.4\rm GHz}\lt 10^{23}$|  W Hz−1), and they show a lack of systems hosting a radio AGN with intermediate radio power (⁠|$2\times 10^{23}\lt P_{1.4\rm GHz}\lt 2\times 10^{24}$|  W Hz−1). We found that the strongest circumnuclear (<1 kpc) X-ray emission only exists in clusters with strong radio AGN. The duty cycle of relaxed, small CC clusters is less than half of that for large CC clusters. It suggests that the radio activity of BCGs is affected by the properties of the surrounding gas beyond the central ∼10 kpc, and strong radio AGNs in small X-ray CCs fade more rapidly than those embedded in large X-ray CCs. A scenario is also presented for the transition of large CCs and coronae due to radio AGN feedback. We also present a detailed analysis of galaxy cluster 3C 129.1 as an example of a CC remnant possibly disrupted by radio AGN. [ABSTRACT FROM AUTHOR]

Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN's Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations. Relativistic electron-positron (pair) plasmas play a fundamental role in the magnetospheres, jets, and winds of black holes and neutron stars, but existing studies have been purely theoretical. Here, the authors open up the exciting possibility to probe relativistic pair-plasmas in the laboratory. [ABSTRACT FROM AUTHOR]

The fourth-DR3 version (4FGL-DR3) of the Fermi -LAT catalogue of γ-ray sources contains ∼1000 objects at a galactic latitude | b | > 10° that are not identified with an optical counterpart. We performed a systematic study of these sources, focusing on 190 objects that have a unique X-ray counterpart in the available Swift /XRT observations. Optical counterparts were then selected, and optical spectra were found in the literature for 33 sources. We found that 21 could be classified as BL Lac objects. Among these, we were able to provide the redshift for eight of them, while for two others we established a lower limit to the redshift by detecting intervening absorption. The other 12 objects display optical spectra with prominent emission lines (0.036 <  z  < 1.65). These spectra are characterized by both broad and narrow emission lines, with the exception of three sources. One of these displays only broad emission lines, while the other two exclusively exhibit narrow lines. On the basis of the radio/optical flux ratio, all BL Lac objects in this study are radio-loud. Four sources out of the 12 with prominent emission lines can be classified as radio-loud, while at least five of the 12 sources with prominent lines are radio-quiet. This is somewhat unexpected, given the radio-loudness distribution of 4FGL-associated blazars. [ABSTRACT FROM AUTHOR]

One of the promising mechanisms to explain the stable jet speed of SS 433 is the magic speed, which is established by the balance between radiation pressure and radiation drag (and gravity). We examine the magic speed in the optically thick sub-relativistic flows for several typical situations, such as plane-parallel and spherical cases, and show that it is difficult to establish the magic speed in the simple optically thick flows in contrast to the optically thin ones. Instead, we propose the funnel jets as an improved model. That is, we consider the optically thick flows in the funnel, which is formed by the supercritical accretion disk, and mass and radiation energy are injected from the funnel wall. In this model the mass-accretion rate determines the configuration of the funnel, the increasing mass-loss rate of jets, the radiative environments, and then the sub-relativistic magic speed is naturally established. [ABSTRACT FROM AUTHOR]

Self-generated magnetic field and electron jet are observed when ultra-intense lasers (> 1 × 10 18 W / c m 2 ) interact with plasma. It is found that the self-generated magnetic field plays a significant role in the generation of electron jets. The generation mechanism of electron jets under the influence of a self-generated circular magnetic field is examined. It is revealed that magnetic modulation of self-generated magnetic fields can result in the collapse of these fields, consequently leading to the production of electron jets. Furthermore, it has been discovered that the velocity of the electron jets is associated with the maximum growth rate of the modulational instability. As the maximum growth rate of the modulational instability decreases, the velocity of the electron jets is reduced. The present work aids in getting a deeper understanding of the generation of electron jets in relativistic laser plasmas. [ABSTRACT FROM AUTHOR]

X-ray and MeV polarization can be powerful diagnostics for leptonic and hadronic blazar models. Previous predictions are mostly based on a one-zone framework. However, recent IXPE observations of Mrk 421 and 501 strongly favor a multizone framework. Thus, the leptonic and hadronic polarization predictions need to be revisited. Here we identify two generic radiation transfer effects, namely, double depolarization and energy stratification, that can have an impact on the leptonic and hadronic polarization. We show how they are generalized from previously known multizone effects of the primary electron synchrotron radiation. Under our generic multizone model, the leptonic polarization degree is expected to be much lower than the one-zone prediction, unlikely detectable in most cases. The hadronic polarization degree can reach a value as high as the primary electron synchrotron polarization during simultaneous multiwavelength flares, consistent with the one-zone prediction. Therefore, IXPE and future X-ray and MeV polarimeters such as eXTP, COSI, and AMEGO-X, have good chances to detect hadronic polarization during flares. However, the hadronic polarization cannot be well constrained during the quiescent state. Nonetheless, if some blazar jets possess relatively stable large-scale magnetic structures, as suggested by radio observations, a nontrivial polarization degree may show up for the hadronic model after a very long exposure time (≳1 yr). [ABSTRACT FROM AUTHOR]

Energy equipartition and the energy budget in the jet are important issues for the radiation mechanism of blazars. Early work predominantly concentrated on flat-spectrum radio quasars and a limited number of BL Lacertae (BL Lac) objects. In this paper, we compile 348 high-frequency peaked BL Lac objects (HBLs) based on the catalog of active galactic nuclei (4LAC-DR3) from Fermi-LAT, and employ JetSet to fit the spectral energy distributions (SEDs) of these HBLs in the framework of the one-zone lepton model. We aim to determine whether the energy budget is reasonable and whether energy equipartition is satisfied in HBLs. The results of the statistical analysis suggest that: (1) SEDs of HBLs can be reproduced well by using the one-zone lepton model; however, it cannot achieve energy equalization, and the relativistic electron energy density is far greater than the magnetic field energy density, U e ≳ 100 U B ; (2) the majority of HBLs are located in the t cool < t dyn region (where the horizontal coordinate represents the jet power of electrons, while the ordinate indicates the ratio of the dynamic timescale to the cooling timescale), and the jet kinetic power of HBLs is greater than the jet power of radiation; there is a very low radiation efficiency, we deduce that HBLs may have optically thin advection-dominated accretion flows; (3) log ϵ B of HBLs is less than zero, which indicates that the jet kinetic power of HBLs is not affected by Poynting flux; (4) the relationships U e > U Syn ∼ U B , L e ∼ L p > L B ∼ L rad, and log ϵ e > 0.5 are established. These relations indicate that most of the energy of HBLs is stored in the population of low-energy electrons. [ABSTRACT FROM AUTHOR]

X-ray polarimetry has been suggested as a prominent tool for investigating the geometrical and physical properties of the emissions from active galactic nuclei (AGN). The successful launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 9 December 2021 has expanded the previously restricted scope of polarimetry into the X-ray domain, enabling X-ray polarimetric studies of AGN. Over a span of two years, IXPE has observed various AGN populations, including blazars and radio-quiet AGN. In this paper, we summarize the remarkable discoveries achieved thanks to the opening of the new window of X-ray polarimetry of AGN through IXPE observations. We will delve into two primary areas of interest: first, the magnetic field geometry and particle acceleration mechanisms in the jets of radio-loud AGN, such as blazars, where the relativistic acceleration process dominates the spectral energy distribution; and second, the geometry of the hot corona in radio-quiet AGN. Thus far, the IXPE results from blazars favor the energy-stratified shock acceleration model, and they provide evidence of helical magnetic fields inside the jet. Concerning the corona geometry, the IXPE results are consistent with a disk-originated slab-like or wedge-like shape, as could result from Comptonization around the accretion disk. [ABSTRACT FROM AUTHOR]

In situ x-ray diffraction was performed on shock-generated microjets composed of Sn and Sn–4Ag. Under low pressure drives (∼21 GPa), a significant fraction of the jet volume was found to be in the β - Sn phase, and these crystallites were much smaller than the initial grain size of the material. Significant quantities of amorphous (molten) material were observed for higher drive pressures (∼25–35 GPa). The extent of melting at these pressures was greater than would be predicted for uniaxial shock loading. Diffraction patterns from the Sn–4Ag alloy showed a peak that is consistent with the expected Ag3Sn intermetallic phase. This peak remained evident under drive conditions where the sample was otherwise fully amorphous. This indicates a slushy or a mixed phase of liquid Sn and solid Ag3Sn. Given the eutectic character of this alloy, this observation is attributed to a kinetic limitation on the dissolution of Ag3Sn. This implies that a much broader range of drive conditions will lead to mixed phase jets and ejecta than would be predicted from the equilibrium melt boundary of such alloys. [ABSTRACT FROM AUTHOR]

Precise measurements of black hole (BH) masses are necessary to understand the coevolution of these sources and their host galaxies. Sometimes in the center of a galaxy, there is not one but two BHs. The BH duality of the quasar nucleus SDSS J075217.84 + 193542.2 (herein referred to as SDSS J0752) was recently proposed based on the observed strict periodicity of optical emission from the source. We tested this assumption using X-ray observations obtained using Swift/XRT (2008-2010). We fitted the SDSS J075217 spectrum using a Comptonization model and discovered soft X-ray variability in the 0.3-10- keV energy range. We pursued a scenario in which two supermassive BHs at the center of SDSS J0752 form a pair, and the less massive (secondary) BH periodically crosses/punctures the disk around the more massive (primary) BH. We associated these periodic crossings with tidal disruptions of the disk and, as a consequence, with an increase in X-rays observed as a flare in SDSS J0752. During such an X-ray flare event (2008-2010), we discovered a change in the source spectral states and the photon index saturation at the Γ ~ 3 level with mass accretion rate Ṁ. For BH mass scaling, we used OJ 287, M101 ULX-1, and HLX-1 ESO 243-49 as reference sources and found that M[sub SDSS] =9 x107 solar masses, assuming that d[sub SDSS] =500 Mpc. Thus, we obtained a lower limit to a BH mass due to the unknown inclination. In addition, we used the virial mass of the secondary BH based on H[sub α]-line measurements, and we estimated the inclination of the binary at SDSS J0752, i =80°, using a scaling technique. [ABSTRACT FROM AUTHOR]

Jets are endemic to both Galactic solar mass and extragalactic supermassive black holes. A recent 86 GHz image of M 87 shows a jet emerging from the accretion ring around a black hole, providing the first direct observational constraint on the kinematics of the jet-launching region in any black hole jetted system. The very wide (∼280 μas), highly collimated, limb-brightened cylindrical jet base is not predicted in current numerical simulations. The emission was shown to be consistent with that of a thick-walled cylindrical source that apparently feeds the flow that produces the bright limbs of the outer jet at an axial distance downstream of 0.4 mas < z < 0.65 mas. The analysis here applies the conservation laws of energy, angular momentum, and magnetic flux to the combined system of the outer jet, the cylindrical jet, and the launch region. It also uses the brightness asymmetries of the jet and counterjet to constrain the Doppler factor. The only global solutions have a source that is located < 34 μas from the event horizon. This includes the Event Horizon Telescope annulus of emission and the regions interior to this annulus. The axial jet begins as a magnetically dominated flow that spreads laterally from the launch radius (< 34 μas). It becomes super-magnetosonic before it reaches the base of the cylindrical jet. The flow is ostensibly redirected and collimated by a cylindrical nozzle formed in a thick accretion disk. The flow emerges from the nozzle as a mildly relativistic (0.3c < v < 0.4c) jet with a significant protonic kinetic energy flux. [ABSTRACT FROM AUTHOR]

Context. Understanding the mechanisms that launch and shape powerful relativistic jets from supermassive black holes (SMBHs) in high-redshift active galactic nuclei (AGNs) is crucial for probing the co-evolution of SMBHs and galaxies over cosmic time. Aims. We focus on the high-redshift (z = 3.396) blazar OH 471 to explore the jet launching mechanism in the early Universe. Methods. Using multi-frequency radio monitoring observations and high-resolution Very Long Baseline Interferometry (VLBI) imaging over three decades, we studied the milliarcsecond structure and long-term variability of OH 471. Results. Our spectral modeling of the radio flux densities revealed a synchrotron self-absorbed spectrum, indicating strong magnetic fields within the compact core. By applying the flux freezing approximation, we estimated the magnetic flux carried by the jet. We found that it reaches or exceeds theoretical predictions for jets powered by black hole spin energy via the Blandford-Znajek mechanism. This implies that OH 471 is in a magnetically arrested disk (MAD) state, where the magnetic flux accumulated near the horizon regulates the accretion flow, allowing for an efficient extraction of black hole rotational energy. Conclusions. Our study demonstrates the dominance of MAD accretion in powering the prominent radio flares and relativistic jets observed in the radio-loud AGN named OH 471. Statistical studies of larger samples of high-redshift AGNs will shed light on the role of MAD accretion in launching and accelerating the earliest relativistic jets. [ABSTRACT FROM AUTHOR]

Aims. The X-ray luminous and radio-loud active galactic nucleus (AGN) SRGE J170245.3+130104 discovered at z ∼ 5.5 provides unique chances to probe the growth and evolution of a supermassice black hole (SMBH) with powerful jets in the early Universe. Methods. We present 1.35 − 5.1 GHz Very Long Baseline Array (VLBA) results regarding the radio continuum emission and a spectral analysis of this quasar in a low-flux-density state. Results. This source is unresolved at three frequencies, with total flux densities of 8.35 ± 0.09 Jy beam−1, 7.47 ± 0.08 Jy beam−1, and 6.57 ± 0.02 Jy beam−1 at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the brightness temperature is higher than 109 K. Conclusions. Compared with previous radio observations with arcsecond-scale resolution, nearly all the radio emission from this source is concentrated in the very central milliarcsecond (mas) scale area. We confirm this source is a bright blazar at z > 5. This young AGN provides a great opportunity to understand the mechanisms behind the generation of strong jets in the early Universe. [ABSTRACT FROM AUTHOR]

Context. Unusually, there are still certain characteristics of the changing-look (CL) active galactic nuclei (AGNs) that remain undetected. Consequently, the trigger mechanism behind the CL phenomenon observed in partial AGNs remains unknown. Aims. We explore the light curve and spectral energy distribution (SED) of the CL blazar OQ 334 as obtained by Fermi-LAT. Methods. By examining the variability of the equivalent width (EW), we categorise the Fermi-LAT light curves of OQ 334 during the epoch of MJD 54628−58677 into seven distinct epochs, including the flat spectrum radio quasar (FSRQ) state, the transition state, and the BL Lac state. We obtained both a Fermi-LAT SED and a multi-wavelength SED for each of these distinct epochs. Results. The source exhibits a transformation from a quiescent state to a highly active state, as evidenced by the variability of the EW. The multi-wavelength SEDs display a prominent external Compton characteristic, even though the Fermi-LAT SED reveals both a FSRQ and a BL Lac state across the seven different epochs. To gain further insights, we employed a leptonic model that takes into account the soft photon fields originating from both synchrotron radiation and the external environment. By simulating the multi-wavelength SEDs for each epoch, we uncover the following results. Firstly, the energy density of the external photon fields evolves in an oscillatory manner over the seven different epochs. Also, the energy density of the external photon fields in the BL Lac state is lower than that in the FSRQ state. Conclusions. These findings suggest that the CL blazar represents a unique phase in the blazar sequence. Considering that the energy density of the external photon fields is proportional to the accretion rate, we propose that evidence for the interconversion of advection-dominated accretion flow (ADAF) discs and standard Shakura–Sunyaev discs (SSDs), – as variations in accretion modes in the CL blazar – can be obtained through observations by Fermi-LAT. [ABSTRACT FROM AUTHOR]

An increasing number of observations and simulations suggests that low-power (< 1044 erg s−1) jets may be a significant channel of feedback produced by active galactic nuclei (AGN), but little is known about their actual effect on their host galaxies from the observational point of view. We targeted four luminous type 2 AGN hosting moderately powerful radio emission (∼1044 erg s−1), two of which and possibly a third are associated with jets, with optical integral field spectroscopy observations from the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT) to analyze the properties of their ionized gas as well as the properties and effects of ionized outflows. We combined these observations with Very Large Array (VLA) and e-MERLIN data to investigate the relations and interactions between the radio jets and host galaxies. We detected ionized outflows as traced by the fast bulk motion of the gas. The outflows extended over kiloparsec scales in the direction of the jet, when present. In the two sources with resolved radio jets, we detected a strong enhancement in the emission-line velocity dispersion (up to 1000 km s−1) perpendicular to the direction of the radio jets. We also found a correlation between the mass and the energetics of this high-velocity dispersion gas and the radio power, which supports the idea that the radio emission may cause the enhanced turbulence. This phenomenon, which is now being observed in an increasing number of objects, might represent an important channel for AGN feedback on galaxies [ABSTRACT FROM AUTHOR]

The secondary processes driven by the velocity shear driven Kelvin‐Helmholtz Instability (KHI) in the magnetized plasmas have been shown to be important in producing plasma transport and heating from the shocked solar wind into the Earth's magnetosphere (MSP). The plasma transport into the MSP due to KHI has been shown to be strongest during northward interplanetary magnetic field (IMF) via KHI driven low‐ and mid‐latitude reconnection process. In a recent article, Li et al. (2023), https://doi.org/10.1029/2023gl105539 show Magnetosphere Multi‐Scale (MMS) spacecraft observations of multiple, Alfvénic reconnection jets during southward IMF at the dawn‐side MSP flank. The quasi‐periodic oscillations in plasma parameters and compressed, ion‐scale current sheets were strongly indicative of the MMS crossing regions of MSP‐like and magnetosheath‐like plasma within Kelvin‐Helmholtz waves. In this brief commentary, the importance of this new discovery for magnetospheric and solar wind dynamics is discussed. Plain Language Summary: Earth's magnetic field serves as a protective barrier, forming a magnetic bubble known as the magnetosphere in the solar wind. Acting like a shield, the magnetopause is a crucial surface that delineates the separation between the solar wind and the plasma enveloped within Earth's magnetosphere. However, this shield is not impervious; a phenomenon called magnetic reconnection can compromise it, permitting direct access for solar wind plasma. This process is particularly effective when the interplanetary magnetic field (IMF) carried by the solar wind opposes Earth's magnetic field direction, a configuration known as "southward" IMF. Under these conditions, the Earth's magnetic field opens at the dayside, facilitating the accumulation of mass, momentum, and energy into the night‐side magnetotail. In a recent discovery, NASA's four Magnetosphere Multiscale spacecraft revealed that magnetic reconnection can also occur during southward IMF at the tail flanks of our magnetic bubble. This reconnection, strongly driven by colossal waves with wavelengths of 56,000 km (Kelvin‐Helmholtz waves) creates portals in our magnetic shield, enabling both the escape and entry of particles. In this brief commentary, the importance of this finding is discussed, both for magnetospheric and solar wind dynamics. Key Points: Kelvin‐Helmholtz Instability (KHI) can generate compressed current sheets, effectively driving magnetic reconnection at flanks during southward interplanetary magnetic fieldKHI driven reconnection can aid energetic particle escape from the magnetosphereKHI driven reconnection may also play role for energetic particle dynamics within solar wind structures [ABSTRACT FROM AUTHOR]

We consider the broad-band spectral energy distribution of the high-energy-peaked blazar Mkn 501 using Swift -XRT/UVOT, NuSTAR and Fermi -LAT observations taken between 2013 and 2022. The spectra were fitted with a one-zone leptonic model using synchrotron and synchrotron self-Compton emission from different particle energy distributions such as a broken power law, log-parabola, as well as distributions expected when the diffusion or the acceleration time-scale are energy-dependent. The jet power estimated for a broken power-law distribution was ∼1047(1044) erg s−1 for a minimum electron energy γmin ∼ 10(103). However, for electron energy distributions with intrinsic curvature (such as the log-parabola form), the jet power is significantly lower at a few times 1042 erg s−1 which is a few per cent of the Eddington luminosity of a 107 M⊙ black hole, suggesting that the jet may be powered by accretion processes. We discuss the implications of these results. [ABSTRACT FROM AUTHOR]

We present new JWST NIRSpec integral field spectroscopy (IFS) data for the luminous infrared galaxy NGC 7469, a nearby (70.6 Mpc) active galaxy with a Seyfert 1.5 nucleus that drives a highly ionized gas outflow and a prominent nuclear star-forming ring. Using the superb sensitivity and high spatial resolution of the JWST instrument NIRSpec IFS, we investigate the role of the Seyfert nucleus in the excitation and dynamics of the circumnuclear gas. Our analysis focuses on the [Fe ii ], H2, and hydrogen recombination lines that trace the radiation/shocked-excited molecular and ionized interstellar medium around the active galactic nucleus (AGN). We investigate gas excitation through H2/Br γ and [Fe ii ]/Pa β emission line ratios and find that photoionization by the AGN dominates within the central 300 pc of the galaxy except in a small region that shows signatures of shock-heated gas; these shock-heated regions are likely associated with a compact radio jet. In addition, the velocity field and velocity dispersion maps reveal complex gas kinematics. Rotation is the dominant feature, but we also identify noncircular motions consistent with gas inflows as traced by the velocity residuals and the spiral pattern in the Pa α velocity dispersion map. The inflow is 2 orders of magnitude higher than the AGN accretion rate. The compact nuclear radio jet has enough power to drive the highly ionized outflow. This scenario suggests that the inflow and outflow are in a self-regulating feeding–feedback process, with a contribution from the radio jet helping to drive the outflow. [ABSTRACT FROM AUTHOR]

The issue of radiation mechanisms triggered in 1950–60s the first applications of plasma physics to understand the nature of radio galaxies. This interplay has steadily intensified during the past five decades due to the premise of in-situ acceleration of relativistic electrons occurring in the lobes of radio galaxies. This article briefly traces the chain of these remarkable developments, largely from an observational perspective. We recount several observational and theoretical milestones established along the way and the lessons drawn from them. We also present a new observational clue about in-situ acceleration of the relativistic particles radiating in the lobes of radio galaxies, gleaned by us from the very recently published sensitive radio observations of a tailed radio source in the galaxy cluster Abell 1033. [ABSTRACT FROM AUTHOR]

Blazars, a subclass of active galactic nuclei (AGN), are known to be bright γ-ray sources, frequently exhibiting active (flaring) periods. Blazar PKS 2155-304 is a high synchrotron-peaked BL Lac object located at redshift z  = 0.116. On 2006 July 28, an extremely remarkable outburst of VHE γ-ray emission from this blazar was reported by the H.E.S.S. experiment, with an average flux more than 10 times the low-state level. The variability time-scale of this extraordinary flare was as short as approximately 200 s. In order to guarantee the transparency of the emission region for TeV photons, the fast variability demands an extremely high Doppler factor δD > 50 of the jet within the classical one-zone model, leading to the so-called 'Doppler factor crisis'. Here, we demonstrate that the stochastic dissipation model, which is a multiblob scenario for blazars, can self-consistently explain the giant TeV flares of PKS 2155-304 and the low-state emission before and after the flares, in terms of both multiwavelength spectral and variability characteristics. The required Doppler factor in this model can be as low as 20, which is a reasonable and typical value for blazar jets. The obtained model parameters may shed some light on the physical properties of the relativistic jet. [ABSTRACT FROM AUTHOR]

We present the results of a comparison between different methods to estimate the power of relativistic jets from active galactic nuclei (AGN). We selected a sample of 32 objects (21 flat-spectrum radio quasars, 7 BL Lacertae objects, 2 misaligned AGN, and 2 changing-look AGN) from the very large baseline array (VLBA) observations at 43 GHz of the Boston University blazar program. We then calculated the total, radiative, and kinetic jet power from both radio and high-energy gamma-ray observations, and compared the values. We found an excellent agreement between the radiative power calculated by using the Blandford and Königl model with 37 or 43 GHz data and the values derived from the high-energy γ -ray luminosity. The agreement is still acceptable if 15 GHz data are used, although with a larger dispersion, but it improves if we use a constant fraction of the γ -ray luminosity. We found a good agreement also for the kinetic power calculated with the Blandford and Königl model with 15 GHz data and the value from the extended radio emission. We also propose some easy-to-use equations to estimate the jet power. [ABSTRACT FROM AUTHOR]

This paper focuses on the drag and heat flux reduction induced by a counterflowing jet located on the leading edge of the blunt body head in rarefied hypersonic flows using the direct simulation Monte Carlo method. Flow structures in the flowfield, such as detached shock wave, Mach disk, contact surface, jet layer, and recompression shock wave, are all weakened gradually with the increase in the freestream altitude, and they eventually disappear at the altitude of 90 km. The increase in the jet pressure provides a great drag reduction by up to 53% when it increases from 800 to 1600 Pa, but the proportion of drag on the blunt body head to the total drag is only affected slightly by the jet pressure. A noteworthy finding is that further increasing jet pressure almost have no effect on heat flux variation when it is larger than 1200 Pa. On the whole, jet temperature has a quite weak influence on both flow structures and drag, while heat flux on the blunt body head is closely related to jet temperature. The results suggest that jet temperature should vary with that of blunt body surface, and moreover, the optimal jet temperature should be moderately lower than the wall surface temperature. In addition, increasing freestream altitude can provide excellent performance of drag reduction, but it causes non-monotonic variation of heat flux. In view of this, it is worth noting that heat flux on the blunt body head actually increases with altitude when the blunt body is in a severely rarefied atmospheric environment, such as the altitude H > 70 km. [ABSTRACT FROM AUTHOR]

This paper presents the results of MHD simulations of astrophysical and laboratory supersonic jets under a superposition of poloidal ( , ) and toroidal () magnetic fields. It is shown that the escaping matter is quickly collimated by the magnetic field. A shock wave of an elongated shape is formed, which moves from the target to the boundary of the chamber, leaving behind a stable flow. A periodic shock wave structure is observed inside the main conical expanding shock wave. It is shown that the toroidal component of the magnetic field remains in the region throughout the entire calculation and plays a role in the collimation of the flow. The poloidal magnetic field decreases in the region of the jet cone, but remains in the simulation region throughout the calculation and also participates in flow collimation. Thus, both components and take part in the collimation of the flow by the magnetic field. The width of the jet and the opening angle of the cone depend on the magnitude of the magnetic field induction. As the field increases, the jet becomes narrower and the cone angle decreases. Initially, we do not specify the rotation of the jet . However, due to the presence of the field, the substance acquires angular velocity and twists along the axis. The simulation results are in agreement with laboratory jets arising in the experiment at the Neodymium laser installation, and with the previously obtained results of MHD modeling of jet formation separately, in poloidal or toroidal magnetic field. [ABSTRACT FROM AUTHOR]

A brief review of the results of experimental modeling of cosmic jets in superstrong magnetic fields of laser relativistic plasma is given. It is noted that the development of cyclotron instability with the generation of cyclotron radiation plays a key role in a number of processes in a plasma with a magnetic field: self-localization of plasma in the form of solitons, conversion of rotational motion of plasma into translational motion, cyclotron acceleration of charged particles, and separation (stratification) of a plasma jet into separate plasma formations. [ABSTRACT FROM AUTHOR]

Supermassive black holes (SMBH) are believed to influence galaxy evolution through AGN (active galactic nuclei) feedback. Galaxy mergers are key processes of galaxy formation that lead to AGN activity and star formation. The relative contribution of AGN feedback and mergers to star formation is not yet well understood. In radio-loud objects, AGN outflows are dominated by large jets. However, in radio-quiet objects, outflows are more complex and involve jet, wind, and radiation. In this review, we discuss the signatures of AGN feedback through the alignment of radio and UV emissions. Current research on AGN feedback is discussed, along with a few examples of studies such as the galaxy merger system MRK 212, the radio-quiet AGN NGC 2639, and the radio-loud system Centaurus A. Multi-frequency observations of MRK 212 indicate the presence of dual AGN, as well as feedback-induced star-forming UV clumps. The fourth episode of AGN activity was detected in radio observations of the Seyfert galaxy NGC 2639, which also showed a central cavity of 6 kpc radius in CO and UV maps. This indicates that multi-epoch jets of radio-quiet AGN can blow out cold molecular gas, which can further reduce star formation in the center of the galaxies. Recent UV observations of Cen A have revealed two sets of stellar population in the northern star-forming region, which may have two different origins. Recent studies have shown that there is evidence that both positive and negative feedback can be present in galaxies at different scales and times. High-resolution, multi-band observations of large samples of different types of AGN and their host galaxies are important for understanding the two types of AGN feedback and their effect on the host galaxies. Future instruments like INSIST and UVEX will be able to help achieve some of these goals. [ABSTRACT FROM AUTHOR]