Guang-Yao Zhao
A5033827624- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- GNSS positioning and interference
- Neutrino Physics Research
- Superconducting and THz Device Technology
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Statistical and numerical algorithms
- Astrophysics and Star Formation Studies
- Chaos-based Image/Signal Encryption
- Cryptographic Implementations and Security
- Particle Detector Development and Performance
- Particle physics theoretical and experimental studies
- Computational Physics and Python Applications
Instituto de Astrofísica de Andalucía
2020-2024
Max Planck Institute for Radio Astronomy
2024
Max Planck Institute for Research on Collective Goods
2023
Korea Astronomy and Space Science Institute
2013-2022
Wuhan University of Technology
2021
Shanghai Astronomical Observatory
2005-2015
National University of Defense Technology
2014-2015
Yamaguchi University
2015
International Centre for Radio Astronomy Research
2015
The University of Western Australia
2015
Abstract The Galactic center supermassive black hole Sagittarius A* (Sgr A*) is one of the most promising targets to study dynamics accretion and outflow via direct imaging with very long baseline interferometry (VLBI). At 3.5 mm (86 GHz), emission from Sgr resolvable Global Millimeter VLBI Array (GMVA). We present first observations phased Atacama Large Millimeter/submillimeter (ALMA) joining GMVA. Our achieve an angular resolution ∼87 μ as, improving upon previous experiments by a factor...
Abstract We study the kinematics of M87 jet using first-year data KVN and VERA Array (KaVA) large program, which has densely monitored at 22 43 GHz since 2016. find that apparent speeds generally increase from ≈0.3 c ≈0.5 mas base to ≈2.7 ≈20 mas, indicating is accelerated subluminal superluminal on these scales. perform a complementary kinematic analysis by archival Very Long Baseline monitoring observed in 2005–2009 1.7 moving relativistic up ≈5.8 distances 200–410 mas. combine two results...
The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic Center's black hole Sagittarius A*. Here we present first total and linearly polarized intensity images of this source obtained with unprecedented 20 $\mu$as resolution EHT. very compact flat-spectrum radio strong optical variability polarization. In April 2017 was observed quasi-simultaneously EHT (April 5-11), Global Millimeter VLBI Array 3), Very Long Baseline 28), giving novel view at four...
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 contemporaneous ground VLBI 15, 43, 86 GHz. Ground-space fringes were obtained up to projected 3.9 Earth diameters session, record 15.1 snapshot sessions, allowing us image innermost jet an angular resolution ∼50 μ as, highest ever achieved for 287. Comparison...
We report on the observations of quasar NRAO 530 with Event Horizon Telescope (EHT) 2017 April 5-7, when was used as a calibrator for EHT Sagittarius A*. At z=0.902 this is most distant object imaged by so far. reconstruct first images source at 230 GHz, an unprecedented angular resolution $\sim$ 20 $\mu$as, both in total intensity and linear polarization. do not detect variability, allowing us to represent whole data set static images. The reveal bright feature located southern end jet,...
We report the initial results of our high-cadence monitoring program on radio jet in active galaxy M87, obtained by KVN and VERA Array (KaVA) at 22 GHz. This is a pilot study that preceded larger KaVA-M87 program, which currently ongoing. The was mostly performed every two to three weeks from December 2013 June 2014, recording rate 1 Gbps, obtaining data for total 10 epochs. successfully sequence good quality maps revealed rich structure this <~1 mas 20 mas, corresponding physical scales...
High-resolution imaging of supermassive black holes is now possible, with new applications to testing general relativity and horizon-scale accretion relativistic jet formation processes. Over the coming decade, EHT will propose add strategically placed VLBI elements operating at 1.3mm 0.87mm wavelength. In parallel, development next-generation backend instrumentation, coupled high throughput correlation architectures, boost sensitivity, allowing stations be modest collecting area while still...
We study the collimation and acceleration of jets in nearby giant radio galaxy NGC 315, using multifrequency Very Long Baseline Array observations archival High Sensitivity Large data. find that jet geometry transitions from a semi-parabolic shape into conical/hyperbolic at distance $\approx10^5$ gravitational radii. constrain frequency-dependent position core, which we locate base. The profile parabolic region is good agreement with steady axisymmetric force-free electrodynamic solution for...
Recent developments in very long baseline interferometry (VLBI) have made it possible for the Event Horizon Telescope (EHT) to resolve innermost accretion flows of largest supermassive black holes on sky. The sparse nature EHT's $(u, v)$-coverage presents a challenge when attempting highly time-variable sources. We demonstrate that changing (u, v)-coverage EHT can contain regions time over course single observation facilitate dynamical imaging. These optimal typically projected distributions...
Abstract The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international array dedicated to high-frequency (23–43 GHz bands) observations in East Asia. Here, we report imaging three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, M 87. This one initial results KaVA's early operation. Our KaVA images reveal extended outflows with substructures such as knots...
Sagittarius A* (Sgr A*), the Galactic Center supermassive black hole (SMBH), is one of best targets to resolve innermost region SMBH with very long baseline interferometry (VLBI). In this study, we have carried out observations toward Sgr at 1.349 cm (22.223 GHz) and 6.950 mm (43.135 East Asian VLBI Network, as a part multi-wavelength campaign Event Horizon Telescope (EHT) in 2017 April. To mitigate scattering effects, physically motivated kernel model from Psaltis et al. (2018) parameters...
We present the first very-long-baseline interferometric (VLBI) observations of blazar OJ287 carried out jointly with Global Millimeter VLBI Array (GMVA) and phased Atacama Large Millimeter/submillimeter (ALMA) at 3.5 mm on April 2, 2017. Participation phased-ALMA not only has improved GMVA north-south resolution by a factor ~3, but also enabled fringe detection signal-to-noise ratios up to 300 baselines longer than 2 G{\lambda}. The high sensitivity motivated us image data newly developed...
3C 84 (NGC 1275) is a well-studied mis-aligned Active Galactic Nucleus (AGN), which has been active in Gamma rays since at least 2008. We have monitored the source four wavelengths (14 mm, 7 3 mm and 2 mm) using Korean VLBI network (KVN) 2013 as part of interferometric monitoring $\gamma$-ray bright AGN (iMOGABA) program. exhibits radio emission both near central supermassive black hole (SMBH) feature known C1 from moving located to south C3. Other facilities also detected these short-term...
Abstract Radio images of the Galactic Center supermassive black hole, Sagittarius A* (Sgr A*), are dominated by interstellar scattering. Previous studies Sgr have adopted an anisotropic Gaussian model for both intrinsic source and scattering, they extrapolated scattering using a purely λ 2 scaling to estimate properties. However, physically motivated models break all three these assumptions. They also predict that refractive effects will be significant, which been ignored in standard fitting...
We present results of single-epoch very long baseline interferometry (VLBI) observations gamma-ray bright active galactic nuclei (AGNs) using the Korean VLBI Network (KVN) at 22, 43, 86, and 129~GHz bands, which are part a KVN key science program, Interferometric Monitoring Gamma-ray Bright AGNs (iMOGABA). selected total 34 radio-loud 30 sources with flux densities $>6\times10^{-10}$~ph~cm$^{-2}$~s$^{-1}$. Single-epoch multi-frequency target were conducted during 24-hr session on 2013...
Abstract We report the first observation of nearby giant radio galaxy NGC 315 using a global very long baseline interferometry (VLBI) array consisting 22 antennas located across five continents, including high-sensitivity stations, at GHz. Utilizing extensive u v -coverage provided by array, coupled with application recently developed superresolution imaging technique based on regularized maximum-likelihood method, we were able to transversely resolve jet parsec scales for time. Previously...
Abstract Frequency phase transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the nondispersive nature troposphere calibrate high-frequency data using solutions derived at lower frequency. While Korean very long baseline (VLBI) network has pioneered simultaneous multiband systems for routine FPT up an observing frequency 130 GHz, this remains largely untested (sub)millimeter regime. A recent effort been made outfit dual-band...
We study the linear polarization of radio cores eight blazars simultaneously at 22, 43, and 86 GHz with observations obtained by Korean VLBI Network (KVN) in three epochs between late 2016 early 2017 frame Plasma-physics Active Galactic Nuclei (PAGaN) project. investigate Faraday rotation measure (RM) cores; RM is expected to increase observing frequency if core positions depend on due synchrotron self-absorption. find a systematic RMs higher frequencies our targets. The RM--$\nu$ relations...
We study the centimeter- to millimeter-wavelength synchrotron spectrum of core radio galaxy M87 at $\lesssim0.8\,{\rm mas}~\sim110R_{s}$ spatial scales using four years fully simultaneous, multi-frequency VLBI data obtained by Korean Network (KVN). find a spectral index $\alpha$ $\gtrsim-0.37$ ($S\propto \nu^{+\alpha}$) between 22GHz and 129GHz. By combining resolution-matched flux measurements from Very Long Baseline Array (VLBA) 15GHz taking Event Horizon Telescope (EHT) 230GHz in epochs...
We proposed a miniature one-dimensional vibration sensor based on small-diameter fiber Bragg grating in this paper. The working principle and theoretical model of the FBG were deduced established theoretically. A genetic algorithm has been used to globally optimize nonlinear programming problem size sensitivity. modal analysis was carried out by using finite element software verify feasibility optimization results. Then metal 3D printing utilized realize integrated processing miniaturization...
The East Asian Very Long Baseline Interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that currently promoted under joint efforts among China, Japan and Korea. EAVN aims at forming by combining large number of radio telescopes distributed over regions. After the combination Korean (KVN) Exploration Radio Astrometry (VERA) into KaVA, further expansion with in Asia actively promoted. Here we report first imaging results (at 22 43 GHz) bright sources obtained...
Context. In February 2017 the blazar OJ 287, one of best super-massive binary-black-hole-system candidates, was detected for first time at very high energies (VHEs; E > 100 GeV) with ground-based γ -ray observatory VERITAS. Aims. Very energy rays are thought to be produced in near vicinity central engine active galactic nuclei. For this reason, and main goal providing useful information characterization physical mechanisms connected observed teraelectronvolt flaring event, we investigate...
We report the first observation of nearby giant radio galaxy NGC 315 using a global VLBI array consisting 22 antennas located across five continents, including high-sensitivity stations, at GHz. Utilizing extensive $(u,v)$-coverage provided by array, coupled with application recently developed super-resolution imaging technique based on regularized maximum likelihood method, we were able to transversely resolve jet parsec scales for time. Previously known its central ridge-brightened...
Abstract PRINCE is a lightweight block cipher whose size and key are 64‐bit 128‐bit, respectively. The core component of which wrapped by the initial final whitening. c o r e adopts 12‐round SPN structure. This paper exploits some new vulnerabilities from an aspect different previous results, applies truncated differential cryptanalysis to PRINCE. result demonstrates that for several reduced versions PRINCE, there exist 5‐round 6‐round (out 12 rounds) distinguishers. We introduce...