Jet Bending Research Articles

Substructures within Substructures in the Complex Postmerging System A514 Unveiled by High-resolution Magellan/Megacam Weak Lensing

Abell 514 (A514) at z = 0.071 is an intriguing merging system exhibiting highly elongated (∼1 Mpc) X-ray features and three large-scale (300 ∼ 500 kpc) bent radio jets. To dissect this system with its multiwavelength data, it is critical to robustly identify and quantify its dark matter substructures. We present a weak-lensing analysis of A514 using deep Magellan/Megacam observations. Combining two optical band filter imaging data obtained under optimal seeing (∼0.″6) and leveraging the proximity of A514, we achieve a high source density of ∼46arcmin−2 or ∼6940 Mpc−2, which enables high-resolution mass reconstruction. We unveil the complex dark matter substructures of A514, which are characterized by the NW and SE subclusters separated by ∼0.7 Mpc, each exhibiting a bimodal mass distribution. The total mass of the NW subcluster is estimated to be M200cNW=1.08−0.22+0.25×1014M⊙ and is further resolved into the eastern ( M200cNWE=2.6−1.1+1.4×1013M⊙) and western ( M200cNWW=7.1−2.0+2.3×1013M⊙ ) components. The mass of the SE subcluster is M200cSE=1.55−0.26+0.28×1014M⊙ , which is also further resolved into the northern ( M200cSEN=2.9−1.3+1.8×1013M⊙ ) and southern ( M200cSES=8.5−2.6+3.1×1013M⊙ ) components. These four substructures coincide with the A514 brightest galaxies and are detected with significances ranging from 3.3σ to 4.7σ. Comparison of the dark matter substructures with the X-ray distribution suggests that A514 might have experienced an off-axis collision, and the NW and SE subclusters are currently near their apocenters.

A high-resolution radio morphology and polarization of the kiloparsec-scale X-ray jet of PKS 1127−145

We report on new multifrequency Very Large Array (VLA) radio observations and Chandra X-ray observations of a radio-loud quasar with a ∼300 kpc-long jet, PKS 1127−145, during a flaring event detected in γ-rays by the Fermi Large Area Telescope in December 2020. The high angular resolution of the new radio images allows us to disentangle for the first time the kiloparsec-scale inner jet from the core contribution. The inner radio jet, up to 15 kpc from the core, is highly polarized (33 percent) and the magnetic field is parallel to the jet axis. At about 18 arcsecs from the core, the jet slightly bends and we observe a re-brightening of the radio emission and a 90-degree rotation of the magnetic field, likely highlighting the presence of a shock that is compressing the magnetic field to a plane perpendicular to the jet axis, where efficient particle acceleration takes place. At the same position, the X-ray emission fades, suggesting a deceleration of the bulk velocity of the jet after the bend. A change in velocity and collimation of the jet is supported by the widening of the jet profile and the detection of a limb-brightened structure connecting the bending region with the jet termination. The limb-brightened structure might indicate the coexistence of both longitudinal and transverse velocity gradients at the jet bending. There is no evidence of significant brightening of the kiloparsec-scale jet in the radio or X-ray band during the γ-ray flare. The X-ray flux, F2 − 10 keV = (6.24 ± 0.57)×10−12 ergs s−1 cm−2, measured by Chandra from the quasar core is consistent with the flux measured by the X-ray Telescope on board the Neil Gehrels Swift Observatory after the high-energy flare. Our results indicate that the γ-ray flaring region is located within the VLA source core.

Unveiling the bent-jet structure and polarization of OJ 287 at 1.7 GHz with space VLBI

We present total intensity and linear polarization images of OJ 287 at 1.68 GHz, obtained through space-based very long baseline interferometry (VLBI) observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the Very Long Baseline Array (VLBA) and the European VLBI Network (EVN). Ground-space fringes were detected with a maximum projected baseline length of ∼5.6 Earth’s diameter, resulting in an angular resolution of ∼530 μas. With this unprecedented resolution at such a low frequency, the progressively bending jet structure of OJ 287 has been resolved up to ∼10 parsec of the projected distance from the radio core. In comparison with close-in-time VLBI observations at 15, 43, 86 GHz from MOJAVE and VLBA-BU-BLAZAR monitoring projects, we obtain the spectral index map showing the opaque core and optically thin jet components. The optically thick core has a brightness temperature of ∼1013 K, and is further resolved into two sub-components at higher frequencies labeled C1 and C2. These sub-components exhibit a transition from optically thick to thin, with a synchrotron self-absorption (SSA) turnover frequency estimated to be ∼33 and ∼11.5 GHz, and a turnover flux density ∼4 and ∼0.7 Jy, respectively. Assuming a Doppler boosting factor of 10, the SSA values provide the estimate of the magnetic field strengths from SSA of ∼3.4 G for C1 and ∼1.0 G for C2. The magnetic field strengths assuming equipartition arguments are also estimated as ∼2.6 G and ∼1.6 G, respectively. The integrated degree of linear polarization is found to be approximately ∼2.5%, with the electric vector position angle being well aligned with the local jet direction at the core region. This alignment suggests a predominant toroidal magnetic field, which is in agreement with the jet formation model that requires a helical magnetic field anchored to either the black hole ergosphere or the accretion disk. Further downstream, the jet seems to be predominantly threaded by a poloidal magnetic field.

Parsec-scale evolution of the gigahertz-peaked spectrum quasar PKS 0858 − 279

ABSTRACT We conducted multi-epoch, multifrequency parsec-scale studies on the gigahertz-peaked spectrum quasar PKS 0858 − 279 with the Very Long Baseline Array (VLBA). Our observations on 2005 November 26 elucidated a weak core, characterized by an inverted spectrum, and a distinctly bent jet that exhibited a notable bright feature in its Stokes I emission. Through comprehensive analysis of polarization and spectral data, we inferred the formation of a shock wave within this feature, stemming from interactions with a dense cloud in the ambient medium. In this paper, Very Long Baseline Interferometry-Gaia astrometry further reinforces the core identification. With a deep analysis of six additional VLBA epochs spanning from 2007 to 2018, we observed that while the quasar’s parsec-scale structure remained largely consistent, there were discernible flux density changes. These variations strongly imply the recurrent ejection of plasma into the jet. Complementing our VLBA data, RATAN-600 observations of the integrated spectra suggested an interaction between standing and travelling shock waves in 2005. Moreover, our multi-epoch polarization analysis revealed a drastic drop in rotation measure values from 6000 to 1000 rad m−2 within a single year, attributable to diminishing magnetic fields and particle density in an external cloud. This change is likely instigated by a shock in the cloud, triggered by the cloud’s interaction with the jet, subsequently prompting its expansion. Notably, we also observed a significant change in the magnetic field direction of the jet, from being perpendicular post its observed bend to being perpendicular prior to the bend – an alteration possibly induced by the dynamics of shock waves.

The Spatial Arrangement of The Electric Field in the Needle-Plate Electrospinning

<p class="IJASEITAbtract">The electric field distribution of the Neddle-Plate (NP) electrospinning set up has reported due to the simple classical electrodynamics solutions. The charge is assumed to distribute uniformly in the needle (nozzle) and the collector (plate). The electric field has an influence only in the early stage of the electrospinning process. The electric field and the viscosity of the jet fluid have caused the bending of the straight jet. The high viscosity of the fluid can preserve the straight jet length much longer. The electric field gives the initial angular momentum of the jet due to the whipping motion of the jet. For the area away from the nozzle, the electric does not influence the whipping motion. Then the whipping motion solely due to the influence from the charge repulsion of the jet fluid and the evaporation of the solvent.</p>

Probing the Interplay between Jets, Winds, and Multi-phase Gas in 11 Radio-quiet PG Quasars: A uGMRT-VLA Study

We present polarization-sensitive images from the Karl G. Jansky Very Large Array (VLA) at 5 GHz of 11 radio-quiet PG quasars. Based on the radio morphology, spectral index, and polarization properties from the VLA study, coupled with the findings of our previous 685 MHz uGMRT data, we find the presence of low-power jets on subarcsecond and arcsecond scales in nine sources; some show signatures of bent jets. The origin of radio emission remains unclear in the remaining two sources. Of the 11 sources, linear polarization is detected in four of them with fractional polarization ranging between 2% and 21%. In PG 1229+204, the inferred B-field direction is parallel to the local kiloparsec-scale jet direction. The inferred B-fields are transverse to the weak southward extension in PG 0934+013. For PG 0050+124 and PG 0923+129, the relationship between the B-field structure and radio outflow direction remains unclear. Localized or small-scale jet–medium interactions can be inferred across the sample based on the VLA jet kinetic power arguments and polarization data. These may have the potential as a feedback mechanism. We find that the radio properties do not show strong correlations with the star formation, [O iii] and CO quantities published in the literature. The lack of evidence of AGN feedback on the global galaxy properties could be due to the relative timescales of AGN activity and those over which any impact might be taking place.

Discovery of A Large-scale Bent Radio Jet in the Merging Cluster A514

We report a discovery of a large-scale bent radio jet in the merging galaxy cluster A514 (z = 0.071). The radio emission originates from the two radio lobes of the active galactic nucleus (AGN) located near the center of the southern subcluster and extends toward the southern outskirts with multiple bends. Its peculiar morphology is characterized by a 400 kpc “bridge,” a 300 kpc “arc,” and a 400 kpc “tail,” which together contribute to its largest linear size of ∼0.7 Mpc. We find that both the flux and spectral features of the emission change with the distance from the AGN. Also, the “bridge” presents a 60% polarized radio emission, which coincided with an X-ray cold front. Based on our multiwavelength observations, we propose that A514 presents a clear case for the redistribution of an old AGN plasma due to merger-driven gas motions. We support our interpretation with idealized cluster merger simulations employing a passive tracer field to represent cosmic-ray electrons and find that merger-driven motions can efficiently create a cloud of these particles in the cluster outskirts, which later can be reaccelerated by the cluster merger shock and produce radio relics.

A radio-jet-driven outflow in the Seyfert 2 galaxy NGC 2110?

We present a spatially resolved study of the ionized gas in the central 2 kpc of the Seyfert 2 galaxy NGC 2110 and investigate the role of its moderate-luminosity radio jet (kinetic radio power of Pjet = 2.3 × 1043 erg s−1). We used new optical integral-field observations taken with the MEGARA spectrograph at the Gran Telescopio Canarias, which cover the 4300 − 5200 Å and 6100 − 7300 Å ranges with a spectral resolution of R ≃ 5000 − 5900. We fitted the emission lines with a maximum of two Gaussian components, except at the position of the active galactic nucleus (AGN), where we used three. Aided by existing stellar kinematics, we used the observed velocity and velocity dispersion (σ) of the emission lines to classify the different kinematic components. The disk component is characterized by lines with σ ≃ 60 − 200 km s−1. The outflow component has typical values of σ ≃ 700 km s−1 and is confined to the central 2.5″ ≃ 400 pc, which is coincident with the linear part of the radio jet detected in NGC 2110. At the AGN position, the [O III]λ5007 line shows high velocity components that reach at least 1000 km s−1. This and the high velocity dispersions indicate the presence of outflowing gas outside the galaxy plane. Spatially resolved diagnostic diagrams reveal mostly low ionization (nuclear) emitting region-like excitation in the outflow and some regions in the disk, which could be due to the presence of shocks. However, there is also Seyfert-like excitation beyond the bending of the radio jet, which probably traces the edge of the ionization cone that intercepts with the disk of the galaxy. NGC 2110 follows the observational trends between the outflow properties and the jet radio power found for a few nearby Seyfert galaxies. All these pieces of information suggest that part of the observed ionized outflow in NGC 2110 might be driven by the radio jet. However, the radio jet was bent at radial distances of ∼200 pc (in projection) from the AGN, and beyond there, most of the gas in the galaxy disk is rotating.

From amyloid fibrils to microfiber condensates: Tuning microfluidic coextrusion of food-grade β-lactoglobulin-pectin core-shell fibers by changes of protein structure

Protein-based microfibers have potential applications in bioengineering and food but preserving and utilizing the unique nanomechanical properties of their protein building blocks at the micrometer scale remains a challenge. This study investigates the bottom-up fabrication of core-shell fibers by coaxial microfluidic spinning of pectin and β-lactoglobulin in different conformational states (monomeric, amyloid fibrils, shortened amyloid fibrils in their isotropic/nematic phases), gelled in CaCl2 solution. Fiber diameters ranged between 478 and 855 μm (wet state) and 107–135 μm (dry state). They showed clear core-shell cross-sections, except pectin-β-lactoglobulin monomer fibers where the compact protein is presumably understood to diffuse through the pectin matrix. The molecular orientation of the fiber building blocks was expressed as order parameters representing the alignment of pectin chains and amyloid fibrils parallel to the fiber axis calculated from synchrotron wide-angle X-ray scattering (WAXS) with a spatial resolution of 20 μm. Introduction of amyloid fibrils as the protein core increased the Young's modulus from 3.3 to 6.4 GPa and tensile strength from 117 to 182 MPa compared to pure pectin fibers. Increasing the protein core flow rate from 1 to 2 mL/h, however, caused helical bending of the core jet, a decrease in order, and ultimately worsened mechanical performance. Overall, full length amyloid fibrils proved to be more beneficial to the mechanical properties than shortened amyloid fibrils. By providing insight into the relationship between protein conformation, spinning flow rate, and resulting mechanical properties of core-shell microfibers, these results may contribute to the field of novel fibrous protein-based materials.

Wave propagation of bending jet in electrospinning process

The electrospinning process features bending jets in space and solidified nanofibers on a collector. Although electrospun nanofibers have been widely applied, the wave characteristics, especially the first jet bend and tapered envelope cone profile, of bending jets are not fully comprehended. In this work, a spatial normal mode k− is true to characterize the convective instability of a bending jet. Some real wave variables are measured and calculated. It is observed that the first jet bend occurs at the jet end. The instability grows quickly at the early stage of a wave. Underdeveloped dispersive waves are temporally and spatially unstable. When dispersive waves develop to a mature stage, the instability grows slowly, and developed dispersive waves are only spatially unstable. Furthermore, the energy ratio of electric energy to kinematic energy accounts for the wave characteristics of a bending jet. A high energy ratio may stabilize the jet, and a very low energy ratio destabilizes the jet. The stabilizing effect of the high energy ratio suppresses the growth of dispersive waves at the jet source. Once residual charges within the jet trigger small perturbations to the electric field near the plate owing to the Coulomb repulsive effect of like charges, the destabilizing effect of the low energy ratio causes the rapid development of small perturbation first at the jet end. The inhomogeneous distribution of electric energy contributes to the tapered envelope cone profile of a bending jet. Numerically and experimentally, the wave speed is in the order of 1 m/s, and the growth rate is in the order of 102 m−1. The numerical results are in accordance with the experimental results.

A polarization study of three blazars using uGMRT at $$\sim $$600 MHz

We present results from our radio polarimetric study with the upgraded Giant Metrewave Radio Telescope (uGMRT) at Band 4 (550-850 MHz) of 3 blazars: radio-loud quasars 3C390.3, 4C71.07 and BL Lac object 1ES 2344+514. The aim of this study was (i) to carry out a feasibility study for Band 4 polarization with the uGMRT, and (ii) to compare and contrast the kpc-scale polarization properties between the blazar sub-classes. We have detected linear polarization in all the three sources. The degree of linear polarization in the cores of the two quasars is higher than in the BL Lac object, consistent with similar differences observed on parsec-scales in blazars. The highest fractional polarization of 15% is observed in the hotspot region of 3C390.3, which also shows extended polarized lobe structures. 1ES 2344+514 shows a core-halo structure whereas 4C71.07 remains unresolved. A rotation of polarization electric vectors along the northern hotspot of 3C390.3, and the core of 1ES 2344+514, suggest jet bending. Greater depolarization in the southern lobe of 3C390.3 compared to the northern lobe indicates the presence of the `Laing-Garrington effect'. Multi-frequency uGMRT polarimetric data are underway to study the kpc-scale rotation measures across these sources in order to look for differences in the surrounding media.

Observations and Simulations of Radio Emission and Magnetic Fields in Minkowski's Object

We combine new data from the Karl G. Jansky Very Large Array with previous radio observations to create a more complete picture of the ongoing interactions between the radio jet from galaxy NGC 541 and the star-forming system known as Minkowski’s Object (MO). We then compare those observations with synthetic radio data generated from a new set of magnetohydrodynamic simulations of jet–cloud interactions specifically tailored to the parameters of MO. The combination of radio intensity, polarization, and spectral index measurements all convincingly support the interaction scenario and provide additional constraints on the local dynamical state of the intracluster medium and the time since the jet–cloud interaction first began. In particular, we show that only a simulation with a bent radio jet can reproduce the observations.

Large-Eddy Simulation of two secondary air supply strategies in kraft recovery boilers

Kraft recovery boilers are large scale combustion applications operating on black liquor, a common side-product of the pulp industry. Here, a simplified boiler model utilizing Computational Fluid Dynamics (CFD) with Large-Eddy Simulation (LES) and Lagrangian Particle Tracking (LPT) is explored to better understand the secondary air supply system and the dispersion of sprayed droplets. The unsteady nature of the air jets and droplet dispersion in such context advocates the usage of scale-resolving simulations such as LES. In the present exploratory study, the usage of LES in recovery boiler air jet simulations is piloted for the first time. The air supply system is modeled as high-momentum-flux jets injected to a uniform cross-flow. First, the set-up was verified by performing a mesh sensitivity study. The main observed global flow features included the mixing zones, wall jet and jet impact regions, jet bending in cross-flow, and reverse flow downstream of the jets. Two different engineering relevant air supply systems, a staggered and an in-line configuration, were studied and compared in terms of mixing and droplet dispersion. The main findings of the present study are as follows. First, out of the two studied configurations, the staggered one was observed to provide a more uniform downstream temperature field. Second, the in-line configuration was noted to outperform the staggered configuration in droplet dispersion by having 22% less spray-wall impingement and 15% more droplets landing at the bottom of the furnace. Third, different modes for droplet trajectories were identified based on the global flow structures.

The X-shaped Radio Galaxy J0725+5835 is Associated with an AGN Pair

X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and wings). One of the promising models for the peculiar morphology is jet reorientation. To clarify this, we conducted a 5 GHz observation with the European VLBI Network (EVN) of XRG J0725+5835, which resembles the archetypal binary active galactic nuclei (AGNs) 0402+379 in radio morphology, but it is larger in angular size. In our observation, two milliarcsecond-scale radio components with nonthermal radio emission are detected. Each of them coincides with an optical counterpart with similar photometric redshift and (optical and infrared) magnitude, corresponding to dual active nuclei. Furthermore, with the improved Very Large Array (VLA) images, we find a bridge between the two radio cores and a jet bending in the region surrounding the companion galaxy. This further supports the interplay between the main and companion galaxies. In addition, we also report the discovery of an arcsecond-scale jet in the companion. Given the projected separation of ∼100 kpc between the main and companion galaxies, XRG J0725+5835 is likely associated with a dual jetted-AGN system. In both EVN and VLA observations, we find signatures that the jet is changing its direction, which is likely responsible for the X-shaped morphology. For the origin of jet reorientation, several scenarios are discussed.

How Does Environment Affect the Morphology of Radio AGN?

Galaxies hosting Active Galactic Nuclei (AGN) with bent radio jets are used as tracers of dense environments, such as galaxy groups and clusters. The assumption behind using these jets is that they are bent under ram pressure from a dense, gaseous medium through which the host galaxy moves. However, there are many AGN in groups and clusters with jets that are not bent, which leads us to ask: why are some AGN jets affected so much by their environment while others are seemingly not? We present the results of an environmental study on a sample of 185 AGN with bent jets and 191 AGN with unbent jets in which we characterize their environments by searching for neighboring galaxies using a Friends-of-Friends algorithm. We find that AGN with bent jets are indeed more likely to reside in groups and clusters, while unbent AGN are more likely to exist in singles or pairs. When considering only AGN in groups of three or more galaxies, we find that bent AGN are more likely to exist in halos with more galaxies than unbent AGN. We also find that unbent AGN are more likely than bent AGN to be the brightest group galaxy. Additionally, groups hosting AGN with bent jets have a higher density of galaxies than groups hosting unbent AGN. Curiously, there is a population of AGN with bent jets that are in seemingly less dense regions of space, indicating they may be embedded in a cosmic web filament. Overall, our results indicate that bent doubles are more likely to exist in in larger, denser, and less relaxed environments than unbent doubles, potentially linking a galaxy’s radio morphology to its environment.

A New Catalog of Head–Tail Radio Galaxies from the VLA FIRST Survey

Abstract The head–tail (HT) morphology of radio galaxies is seen for a class of radio sources where the primary lobes are being bent in the intercluster weather due to strong interactions between the radio jets and their respective intracluster medium. A systematic search has been carried out for new HT radio galaxies from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters survey database at 1400 MHz. Here, we present a catalog of 717 new HT sources, among which 287 are narrow-angle tail (NAT) sources whose opening angle between the two lobes is less than 90°, and 430 are wide-angle tail (WAT) whose the opening angle between the two lobes is greater than 90°. NAT radio sources are characterized by tails bent in a narrow “V”-like shape; the jet bending in the case of WAT radio galaxies are such that the WATs exhibit wide “C”-like morphologies. Optical counterparts are found for 359 HT sources. We report HT sources with luminosity ranges 1038 ≤ L 1.4 GHz ≤ 1045 erg s−1 and redshifts up to 2.01. The various physical properties of these HT sources are mentioned here. Some statistical studies have been done for this large number of newly discovered HT sources.

Droplet impact dynamics onto a deep liquid pool of wavy free surface

The impact of a droplet on a deep pool of water with a flat-free surface results in a deep cavity followed by the emergence of a thick jet with a secondary drop when the Froude number and Weber number of the impacting droplet are 220 and 252, respectively. The disturbances in the free surface of the liquid pool modify the crater and the jet dynamics under identical drop impact conditions. Here, we present the simulations of the water drop impact on a deep liquid pool having various wavy profiles mimicking the free surface ripples. Long slender jets with the formation of multiple secondary droplets are observed when the droplet impacts the trough of an axisymmetric wavy surface. The influence of wave number on the wavy profile becomes more pronounced at large wave amplitudes. While capillary-inertia instability governs the pinch-off of thick Worthington jets, the pinch-off of these slender jets is found to be mainly inertia driven. However, if the drop impacts the crest of an axisymmetric wave, a short thick jet forms with one or two secondary droplets. Axisymmetric waves with radially outward moving interface, as in ripples, showed the occurrence of complete coalescence when droplet impacted on the crest; but the dynamics remain mostly the same as that of a stationary wave for the droplet impact on a trough. Entrainment of air bubbles after cavity collapse and bent jet occurred for an impact on a sinusoidal planar wave when the impact location was in between the two consecutive extremes.

Role of the companion lensing galaxy in the CLASS gravitational lens B1152+199

ABSTRACT We reinvestigate the Cosmic Lens All-Sky Survey (CLASS) gravitational lens B1152+199 using archived Hubble Space Telescope (HST) data and Very Long Baseline Interferometry (VLBI) data. A consistent luminosity ratio within effective radius between the host galaxy and the X-galaxy is measured from HST tri-band images, which leads to a mass ratio between the two galaxies as rb ∼ 2. To determine the role of the X-galaxy in the lens system, we modelled the dual-lens system with constraints from the VLBI-resolved jet components and the HST images. The 8.4-GHz global-VLBI data currently provide the most stringent constraints to the mass model, especially to the radial power-law slope. The optimized models for this two-image three-component radio lens favour a steeper-than-isothermal inner slope. The jet bending in image B was also investigated and it turned out to be rather a misalignment than a curvature. The goodness-of-fit indicates that the role of the X-galaxy is crucial in the lens system if three pairs of resolved jet components are to be fitted. When we imported the optimal model from radio constraints to optical modelling with the HST tri-band data, the optimization kept the consistency of the optimal model and successfully reproduced the features observed in the HST images. This implies that the diffuse emission discovered in the HST images is actually a detection of the secondary lensing effects from the companion lens.

Bending of a Viscous Jet Emanating from a Capillary

Bending of a Viscous Jet Emanating from a Capillary

Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287

Abstract We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth diameters during the snapshot sessions, allowing us to image the innermost jet at an angular resolution of ∼50μ as, the highest ever achieved at 22 GHz for OJ 287. Comparison with ground-based VLBI observations reveals a progressive jet bending with increasing angular resolution that agrees with predictions from a supermassive binary black hole model, although other models cannot be ruled out. Spectral analyses suggest that the VLBI core is dominated by the internal energy of the emitting particles during the onset of a multiwavelength flare, while the parsec-scale jet is consistent with being in equipartition between the particles and magnetic field. Estimated minimum brightness temperatures from the visibility amplitudes show a continued rising trend with projected baseline length up to 1013 K, reconciled with the inverse-Compton limit through Doppler boosting for a jet closely oriented to the line of sight. The observed electric vector position angle suggests that the innermost jet has a predominantly toroidal magnetic field, which, together with marginal evidence of a gradient in rotation measure across the jet width, indicates that the VLBI core is threaded by a helical magnetic field, in agreement with jet formation models.