arXiv subjects

Sascha Trippe

Publications and source records attributed to Sascha Trippe.

At least 19 recordsLinked to original sources

arXiv2026

A Unified Origin of Faraday Rotation toward 3C 84: The Circumnuclear Ambient Medium within the Parsec-Scale Bondi Radius of the Host Galaxy NGC 1275

We present multi-frequency polarimetric observations of 3C 84 obtained with the Korean VLBI Network at 43-141 GHz, the Very Long Baseline Array at 43 GHz, and the High Sensitivity Array at 8 GHz from 2015 to 2024. We find that the Faraday rotation measure (RM) decreases systematically with distance from the black hole over 1-8 pc, following a single power-law trend of RM proportional to r^{-2.7+/-0.2}. Notably, RM measurements from earlier studies across the same distance range follow the same relation. This consistency across epochs, frequencies, and independent datasets indicates a common and stable external Faraday screen. These results naturally identify the circumnuclear ambient medium within the parsec-scale Bondi radius of the host galaxy NGC 1275 as the origin of the Faraday rotation, thereby resolving a long-standing question about its physical origin. From the RM profile, we derive radial distributions of the electron density and magnetic-field strength in the circumnuclear ambient medium that are consistent with independent constraints. The derived density lies below that of the free-free absorption disk and, when extrapolated inward, remains below the density of the broad-line region. The magnetic-field strength gradually increases from 0.1-1.5 microgauss at the Bondi radius to milligauss-to-gauss levels toward the black hole, providing the first spatially resolved constraint on the magnetic-field strength at parsec-scale distances in an elliptical galaxy. Together, these results present a spatially resolved and physically consistent picture of the circumnuclear environment in NGC 1275.

astro-ph.GA↗

arXiv2025

Monitoring of 3C 286 with ALMA, IRAM, and SMA from 2006 to 2025: Stability, Synchrotron Ages, and Frequency-Dependent Polarization Attributed to Core-Shift

We present the results of multi-frequency monitoring of the radio quasar 3C 286, conducted using three instruments: ALMA at 91.5, 103.5, 233.0, and 343.4 GHz, the IRAM 30-m Telescope at 86 and 229 GHz, and SMA at 225 GHz. The IRAM measurements from 2006 to 2024 show that the total flux of 3C 286 is stable within measurement uncertainties, indicating long-term stability up to 229 GHz, when applying a fixed Kelvin-to-Jansky conversion factor throughout its dataset. ALMA data from 2018 to 2024 exhibit a decrease in flux, which up to 4% could be attributed to an apparent increase in the absolute brightness of Uranus, the primary flux calibrator for ALMA with the ESA4 model. Taken together, these results suggest that the intrinsic total flux of 3C 286 has remained stable up to 229 GHz over the monitoring period. The polarization properties of 3C 286 are stable across all observing frequencies. The electric vector position angle (EVPA) gradually rotates as a function of wavelength squared, which is well described by a single power-law over the full frequency range. We therefore propose using the theoretical EVPA values from this model curve for absolute EVPA calibration between 5 and 343.4 GHz. The Faraday rotation measure increases as a function of frequency up to (3.2+/-1.5)x10^4 rad m^-2, following RM proportional to nu^alpha with alpha = 2.05+/-0.06. This trend is consistent with the core-shift effect expected in a conical jet.

astro-ph.GA↗

arXiv2025

Polarization flare of 3C 454.3 in millimeter wavelengths seen from decadal polarimetric observations

This study investigates polarimetric characteristics of the blazar 3C~454.3 at 22-129~GHz using decadal~(2011-2022) data sets. In addition, we also delve into the origin of the polarization flare observed in 2019. The data sets were obtained from the single-dish mode observations of the Korean VLBI Network~(KVN) and the 43-GHz Very Long Baseline Array~(VLBA). We compared the consistency of the measurements between milli-arcsecond and arcsecond scales. The Faraday rotation measure values were obtained via two approaches, model fitting to a linear function in all frequency ranges, and calculation from adjacent frequency pairs. We found that the linear polarization angle is preferred to be $\sim100^{\circ}$ when the source is highly polarized. At 43~GHz, we found that the polarized emission at scales of mas and arcsecond is consistent when we compare its flux density and polarization angle. The ratio of quasi-simultaneously measured polarized flux density is $1.02\pm0.07$, and the polarization angles display similar rotation. These suggest that the extended jet beyond the scale of VLBA 43~GHz has a negligible convolution effect on the polarization angle from the KVN. We found an interesting, notable flaring event in the KVN single-dish data from the polarized emission in 2019 in the frequency range of 22-129~GHz. During the flare, the observed polarization angles~($\chi_{\rm obs}$) rotate from $\sim150^{\circ}$ to $\sim100^{\circ}$ at all frequencies with a chromatic polarization degree~($m_{\rm p}$). Based on the observed $m_{\rm p}$ and $\chi_{\rm obs}$, and also the Faraday rotation measure, we suggest that the polarization flare in 2019 is attributed to the shock-shock interaction in the stationary jet region. The change in the viewing angle of the jet alone is insufficient to describe the increase in brightness temperature, indicating the presence of source intrinsic processes.

astro-ph.GA↗

arXiv2025

Enhanced imaging of M87*: Simulations with the EHT and extended-KVN

The Event Horizon Telescope (EHT) has successfully revealed the shadow of the supermassive black hole, M87*, with an unprecedented angular resolution of approximately 20 uas at 230 GHz. However, because of limited short baseline lengths, the EHT has been constrained in its ability to recover larger scale jet structures. The extended Korean VLBI Network (eKVN) is committed to joining the EHT from 2024 that can improve short baseline coverage. This study evaluates the impact of the participation of eKVN in the EHT on the recovery of the M87* jet. Synthetic data, derived from a simulated M87* model, were observed using both the EHT and the combined EHT+eKVN arrays, followed by image reconstructions from both configurations. The results indicate that the inclusion of eKVN significantly improves the recovery of jet structures by reducing residual noise. Furthermore, jackknife tests, in which one or two EHT telescopes were omitted - simulating potential data loss due to poor weather - demonstrate that eKVN effectively compensates for these missing telescopes, particularly in short baseline coverage. Multi-frequency synthesis imaging at 86-230 GHz shows that the EHT+eKVN array enhances the recovered spectral index distribution compared to the EHT alone and improves image reconstruction at each frequency over single-frequency imaging. As the EHT continues to expand its array configuration and observing capabilities to probe black hole physics more in depth, the integration of eKVN into the EHT will significantly enhance the stability of observational results and improve image fidelity. This advancement will be particularly valuable for future regular monitoring observations, where consistent data quality is essential.

astro-ph.IM↗

arXiv2024

Jet Collimation and Acceleration in the Flat Spectrum Radio Quasar 1928+738

Using time-resolved multifrequency Very Long Baseline Array data and new KaVA (KVN and VERA Array) observations, we study the structure and kinematics of the jet of the flat spectrum radio quasar (FSRQ) 1928+738. We find two distinct jet geometries as function of distance from the central black hole, with the inner jet having a parabolic shape, indicating collimation, and the outer jet having a conical shape, indicating free expansion of the jet plasma. Jet component speeds display a gradual outward acceleration up to a bulk Lorentz factor $\Gamma_{\rm max} \approx10$, followed by a deceleration further downstream. The location of the acceleration zone matches the region where the jet collimation occurs; this is the first direct observation of an acceleration and collimation zone (ACZ) in an FSRQ. The ACZ terminates approximately at a distance of 5.6$\times 10^6$ gravitational radii, which is in good agreement with the sphere of gravitational influence of the supermassive black hole, implying that the physical extent of the ACZ is controlled by the black hole gravity. Our results suggest that confinement by an external medium is responsible for the jet collimation and that the jet is accelerated by converting Poynting flux energy to kinetic energy.

astro-ph.HE↗

arXiv2023

Evolution of the Termination Region of the Parsec-Scale Jet of 3C 84 Over the Past 20 Years

We present the kinematics of the parsec-scale jet in 3C 84 from 2003 November to 2022 June observed with the Very Long Baseline Array (VLBA) at 43 GHz. We find that the C3 component, a bright feature at the termination region of the jet component ejected from the core in 2003, has maintained a nearly constant apparent velocity of 0.259 +/- 0.003c over the period covered by observations. We observe the emergence of four new subcomponents from C3, each exhibiting apparent speeds higher than that of C3. Notably, the last two subcomponents exhibit apparent superluminal motion, with the fastest component showing an apparent speed of 1.22 +/- 0.14c. Our analysis suggests that a change in viewing angle alone cannot account for the fast apparent speeds of the new subcomponents, indicating that they are intrinsically faster than C3. We identify jet precession (or reorientation), a jet-cloud collision, and magnetic reconnection as possible physical mechanisms responsible for the ejection of the new subcomponents.

astro-ph.HE↗

arXiv2023

Precessing jet nozzle connecting to a spinning black hole in M87

The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies of the inner region of M87 revealed a wide opening angle for the jet originating near the black hole. The Event Horizon Telescope resolved the central radio source and found an asymmetric ring structure consistent with expectations from General Relativity. With a baseline of 17 years of observations, there was a shift in the jet's transverse position, possibly arising from an eight to ten-year quasi-periodicity. However, the origin of this sideways shift remains unclear. Here we report an analysis of radio observations over 22 years that suggests a period of about 11 years in the position angle variation of the jet. We infer that we are seeing a spinning black hole that induces the Lense-Thirring precession of a misaligned accretion disk. Similar jet precession may commonly occur in other active galactic nuclei but has been challenging to detect owing to the small magnitude and long period of the variation.

astro-ph.HE↗

arXiv2023

The Capella Program: Toward A Space-only High-frequency Radio VLBI Network Formed by Small Satellites in Low Earth Orbits

Very long baseline radio interferometry (VLBI) with ground-based observatories is limited by the size of Earth, the geographic distribution of antennas, and the transparency of the atmosphere. In this whitepaper, we present a design for a space-to-space VLBI program composed of two missions: Mimosa, a pathfinder, and Capella, a science-grade VLBI observatory. Mimosa is a two-element space-to-space radio interferometer composed of two small (250 kg) satellites on co-planar polar circular low Earth orbits. Using single-band, single-circular polarization heterodyne HEMT receivers operating at frequencies around 100 GHz, the interferometer is able to achieve a near-perfect visibility plane coverage and an angular resolution of approximately 35 microarcsec. Capella comprises four small (500 kg) satellites in two orthogonal polar low-Earth orbit planes. With single-band heterodyne receivers operating at frequencies around 690 GHz, the interferometer is able to achieve angular resolutions of approximately 7 microarcsec. Within a total observing time of three days, a near-complete uv plane coverage can be reached. The technology for all key components required - radio telescope, receiver, sampler, recorder, frequency standard, positioning system, data downlink, and pointing control system - is already available, partially off-the-shelf. Capella will be able to address a range of science cases, including: the shadows of supermassive black holes; the acceleration and collimation zones of plasma jets emitted from the vicinity of supermassive black holes; the chemical composition of accretion flows into active galactic nuclei through observations of molecular absorption lines; mapping supermassive binary black holes; the magnetic activity of stars; and nova eruptions of symbiotic binary stars -- and, like any substantially new observing technique, has the potential for unexpected discoveries.

astro-ph.IM↗

arXiv2023

Spectral analysis of a parsec-scale jet in M87: Observational constraint on the magnetic field strengths in the jet

Because of its proximity and the large size of its black hole, M87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magnetic fields are considered to be an essential factor in the launching and accelerating of the jet. However, current observational estimates of the magnetic field strength of the M87 jet are limited to the innermost part of the jet or to HST-1. No attempt has yet been made to measure the magnetic field strength in between. We aim to infer the magnetic field strength of the M87 jet out to a distance of several thousand $r_s$ by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. In order to obtain high-quality spectral index maps, quasi-simultaneous observations at 22 and 43 GHz were conducted using the KVN and VERA Array (KaVA) and the VLBA. We compared the spectral index distributions obtained from the observations with a model and placed limits on the magnetic field strengths as a function of distance. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from $α_{22-43 GHz}$ ~ -0.7 at ~ 2 mas to $α_{22-43 GHz}$ ~ -2.5 at ~ 6 mas. A spectral index model in which nonthermal electron injections inside the jet decrease with distance can adequately reproduce the observed trend. This suggests the magnetic field strength of the jet at a distance of 2 - 10 mas (~ 900 $r_s$ - ~ 4500 $r_s$ in the deprojected distance) has a range of $B=(0.3 - 1.0 G)(z/2 mas)^{-0.73}$. Extrapolating to the EHT scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ~ 4500 $r_s$ without significant dissipation.

astro-ph.HE↗

arXiv2023

Renovation of Seoul Radio Astronomy Observatory and Its First Millimeter VLBI Observations

The Seoul Radio Astronomy Observatory (SRAO) operates a 6.1-meter radio telescope on the Gwanak campus of Seoul National University. We present the efforts to reform SRAO to a Very Long Baseline Interferometry (VLBI) station, motivated by recent achievements by millimeter interferometer networks such as Event Horizon Telescope, East Asia VLBI Network, and Korean VLBI Network (KVN). For this goal, we installed a receiver that had been used in the Combined Array for Research in Millimeter-wave Astronomy and a digital backend, including an H-maser clock. The existing hardware and software were also revised, which had been dedicated only to single-dish operations. After several years of preparations and test observations in 1 and 3-millimeter bands, a fringe was successfully detected toward 3C 84 in 86 GHz in June 2022 for a baseline between SRAO and KVN Ulsan station separated by 300 km. Thanks to the dual frequency operation of the receiver, the VLBI observations will soon be extended to the 1 mm band and verify the frequency phase referencing technique between 1 and 3-millimeter bands.

astro-ph.IM↗

arXiv2022

Using the Crab Nebula as Polarization Angle Calibrator for the Korean VLBI Network

The Crab nebula is widely used as a polarization angle calibrator for single-dish radio observations because of its brightness, high degree of linear polarization, and well-known polarization angle over a wide frequency range. However, the Crab nebula cannot be directly used as a polarization angle calibrator for single-dish observations with the Korean VLBI Network (KVN), because the beam size of the telescopes is smaller than the size of the nebula. To determine the polarization angle of the Crab nebula as seen by KVN, we use 3C 286, a compact polarized extragalactic radio source whose polarization angle is well-known, as a reference target. We observed both the Crab nebula and 3C 286 with the KVN from 2017 to 2021 and find that the polarization angles at the total intensity peak of the Crab nebula (equatorial coordinates (J2000) R.A. $=$ 05$^{\rm h}$34$^{\rm m}$32.3804$^{\rm s}$ and Dec $=$ 22$^\circ$00'44.0982") are $154.2^\circ \pm 0.3^\circ$, $151.0^\circ \pm 0.2^\circ$, $150.0^\circ \pm 1.0^\circ$, and $151.3^\circ \pm 1.1^\circ$ at 22, 43, 86, and 94 GHz, respectively. We also find that the polarization angles at the pulsar position (RA $=$ 05$^{\rm h}$34$^{\rm m}$31.971$^{\rm s}$ and Dec $=$ 22$^\circ$00'52.06") are $154.4^\circ\pm 0.4^\circ$, $150.7^\circ\pm 0.4^\circ$, and $149.0^\circ\pm 1.0^\circ$ for the KVN at 22, 43, and 86 GHz. At 129 GHz, we suggest to use the values $149.0^\circ \pm 1.6^\circ$ at the total intensity peak and $150.2^\circ \pm 2.0^\circ$ at the pulsar position obtained with the Institute for Radio Astronomy in the Millimeter Range (IRAM) 30-meter Telescope. Based on our study, both positions within the Crab nebula can be used as polarization angle calibrators for the KVN single-dish observations.

astro-ph.GA↗

arXiv2022

Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)

The East Asian VLBI Network (EAVN) is an international VLBI facility in East Asia and is operated under mutual collaboration between East Asian countries, as well as part of Southeast Asian and European countries. EAVN currently consists of 16 radio telescopes and three correlators located in China, Japan, and Korea, and is operated mainly at three frequency bands, 6.7, 22, and 43 GHz with the longest baseline length of 5078 km, resulting in the highest angular resolution of 0.28 milliarcseconds at 43 GHz. One of distinct capabilities of EAVN is multi-frequency simultaneous data reception at nine telescopes, which enable us to employ the frequency phase transfer technique to obtain better sensitivity at higher observing frequencies. EAVN started its open-use program in the second half of 2018, providing a total observing time of more than 1100 hours in a year. EAVN fills geographical gap in global VLBI array, resulting in enabling us to conduct contiguous high-resolution VLBI observations. EAVN has produced various scientific accomplishments especially in observations toward active galactic nuclei, evolved stars, and star-forming regions. These activities motivate us to initiate launch of the 'Global VLBI Alliance' to provide an opportunity of VLBI observation with the longest baselines on the earth.

astro-ph.IM↗

arXiv2022

Circumnuclear dense gas disk fuelling the active galactic nucleus in the nearby radio galaxy NGC 4261

The cold molecular gas in the circumnuclear disk (CND) of radio galaxies provides critical information for understanding the mass accretion onto active galactic nuclei. We present the first detection and maps of HCN J=1-0 and HCO+ J=1-0 emission lines from the circumnuclear region of a nearby radio galaxy, NGC 4261, using the Northern Extended Millimeter Array. Both molecular lines are detected at a radial velocity of +-700 km/s relative to the systemic velocity of the galaxy, and they arise from a CND with an outer radius of 100 pc. The velocity fields of HCN and HCO+ are fitted with a Keplerian disk rotation. The enclosed mass is (1.6+-0.1)x10^9 M_solar, assuming a disk inclination angle of 64 degree. The continuum image at 80 GHz reveals a weak two-sided jet structure extending over 5 kpc along the east-west direction and a bright core at the centre. The continuum spectrum between 80 and 230 GHz shows a spectral index of -0.34+-0.02, which suggests optically thin synchrotron radiation. The dense gas mass associated with the CND is calculated to be 6.03x10^7 M_solar. It supports a positive correlation between the dense gas mass in the CND and the accretion rate onto the supermassive black hole, though there are uncertainties in the parameters of the correlation.

astro-ph.GA↗

arXiv2021

The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm

Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of the best targets to resolve the innermost region of SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr A* at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 GHz) with the East Asian VLBI Network, as a part of the multi-wavelength campaign of the Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, the physically motivated scattering kernel model from Psaltis et al. (2018) and the scattering parameters from Johnson et al. (2018) have been applied. As a result, a single, symmetric Gaussian model well describes the intrinsic structure of Sgr A* at both wavelengths. From closure amplitudes, the major-axis sizes are ~704$\pm$102 $μ$as (axial ratio $\sim$1.19$^{+0.24}_{-0.19}$) and $\sim$300$\pm$25 $μ$as (axial ratio $\sim$1.28$\pm$0.2) at 1.349 cm and 6.95 mm respectively. Together with a quasi-simultaneous observation at 3.5 mm (86 GHz) by Issaoun et al. (2019), we show that the intrinsic size scales with observing wavelength as a power-law, with an index $\sim$1.2$\pm$0.2. Our results also provide estimates of the size and compact flux density at 1.3 mm, which can be incorporated into the analysis of the EHT observations. In terms of the origin of radio emission, we have compared the intrinsic structures with the accretion flow scenario, especially the radiatively inefficient accretion flow based on the Keplerian shell model. With this, we show that a nonthermal electron population is necessary to reproduce the source sizes.

astro-ph.HE↗

arXiv2021

Radio and $γ$-ray activity in the jet of the blazar S5 0716$+$714

We explore the connection between the $γ$-ray and radio emission in the jet of the blazar 0716$+$714 by using 15, 37, and 230 GHz radio and 0.1$-$200 GeV $γ$-ray light curves spanning 10.5 years (2008$-$2019). We find significant positive and negative correlations between radio and $γ$-ray fluxes in different time ranges. The time delays between radio and $γ$-ray emission suggest that the observed $γ$-ray flares originated from multiple regions upstream of the radio core, within a few parsecs from the central engine. Using time-resolved 43 GHz VLBA maps we identified 14 jet components moving downstream along the jet. Their apparent speeds range from 6 to 26 $c$, showing notable variations in their position angles upstream the stationary component ($\sim$0.53 mas from the core). The brightness temperature declines as function of distance from the core according to a power-law which becomes shallower at the location of the stationary component. We also find that the periods at which significant correlations between radio and $γ$-ray emission occur overlap with the times when the jet was oriented to the north. Our results indicate that the passage of a propagating disturbance (or shock) through the radio core and the orientation of the jet might be responsible for the observed correlation between the radio and $γ$-ray variability. We present a scenario that connects the positive correlation and the unusual anti-correlation by combining the production of a flare and a dip at $γ$-rays by a strong moving shock at different distances from the jet apex.

astro-ph.HE↗

arXiv2021

A persistent double nuclear structure in 3C 84

3C 84 (NGC 1275) is the radio source at the center of the Perseus Cluster and exhibits a bright radio jet. We observed the source with the Global Millimeter VLBI Array (GMVA) between 2008 and 2015, with a typical angular resolution of $\sim$50 $μ$as. The observations revealed a consistent double nuclear structure separated by $\sim$770 gravitational radii assuming a Black Hole mass of 3.2 $\times 10^{8}$ $M_{\odot}$. The region is likely too broad and bright to be the true jet base anchored in the accretion disk or Black Hole ergosphere. A cone and parabola were fit to the stacked (time averaged) image of the nuclear region. The data did not strongly prefer either fit, but combined with a jet/counter-jet ratio analysis, an upper limit on the viewing angle to the inner jet region of $\leq$35$^{\circ}$ was found. This provides evidence for a variation of the viewing angle along the jet (and therefore a bent jet) within $\sim$0.5 parsec of the jet launching region. In the case of a conical jet, the apex is located $\sim$2400 gravitational radii upstream of the bright nuclear region and up to $\sim$600 gravitational radii upstream in the parabolic case. We found a possible correlation between the brightness temperature and relative position angle of the double nuclear components, which may indicate rotation within the jet.

astro-ph.GA↗

arXiv2021

General relativistic effects on pulsar radiation

The magnetosphere of, and electromagnetic (EM) radiation from pulsars are usually described in the framework of classical electrodynamics. For some pulsars, however, whose emission heights are relatively close to the surface of the neutron star, general relativistic effects might modify the emission from the pulsar. We consider a magnetic dipole model of a pulsar to investigate general relativistic effects on EM radiation from it. Our study includes general relativistic modifications applicable to some significant issues in pulsar astronomy, such as the magnetosphere structure and pulse profiles. We implement computation of the magnetic field in the pulsar magnetosphere from a solution to Maxwell's equations defined in the strongly curved spacetime around a pulsar and find that the field exhibits a strong gravitational effect. The effect modifies curvature radiation of a pulsar, which then leads to modifications of the pulse profiles of radio emission. We take the pulsar PSR J1828-1101 as an example and work out Stokes parameters to simulate the pulse profiles for its main and interpulse emissions theoretically, which exhibit the gravitational effects clearly; however, their testability is beyond the current detection capabilities, with the absolute magnitude of the pulse profiles not being precisely predictable.

astro-ph.HE↗

arXiv2021

East Asian VLBI Network Observations of Active Galactic Nuclei Jets: Imaging with KaVA+Tianma+Nanshan

The East Asian very-long-baseline interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Japan, and Korea. EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions. After the combination of the Korean VLBI Network (KVN) and the VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with the joint array in East Asia is actively promoted. Here we report the first imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test the EAVN imaging performance for different sources, we observed four active galactic nuclei (AGN) having different brightness and morphology. As a result, we confirmed that Tianma 65-m Radio Telescope (TMRT) significantly enhances the overall array sensitivity, a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of KaVA only. The addition of Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular resolution. With the resulting high-dynamic-range, high-resolution images with EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as the counter-jet in M87, a kink-like morphology of the 3C273 jet and the weak emission in other sources, are successfully detected. This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general. Ongoing expansion of EAVN will further enhance the angular resolution, detection sensitivity and frequency coverage of the network.

astro-ph.GA↗