Fumie Tazaki
A5058220707- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Particle Accelerators and Free-Electron Lasers
- Optical measurement and interference techniques
- Astronomical Observations and Instrumentation
- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Mechanics and Biomechanics Studies
- Advanced X-ray Imaging Techniques
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Digital Holography and Microscopy
- Ionosphere and magnetosphere dynamics
- Superconducting and THz Device Technology
- Soil Moisture and Remote Sensing
- Precipitation Measurement and Analysis
- Nutrition and Health in Aging
- Scientific Measurement and Uncertainty Evaluation
- Health and Well-being Studies
- Black Holes and Theoretical Physics
Korea Astronomy and Space Science Institute
2025
Korean Association for the Study of Intestinal Diseases
2025
Tokyo Electron (Japan)
2022-2024
National Astronomical Observatory of Japan
2014-2024
Fujitsu (United States)
2024
Tokyo Electron (Ireland)
2023
National Institutes of Natural Sciences
2020
Kyoto University
2010-2014
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of in 2017, at wavelength 1.3 mm, revealed ring-like structure, which was interpreted as gravitationally lensed emission around central hole3. Here we report images obtained 2018, 3.5 showing that the compact core spatially resolved. High-resolution imaging shows structure [Formula: see text] Schwarzschild radii diameter, approximately 50% larger than...
We report on results from new high-sensitivity, high-resolution 86GHz (3.5 millimeter) observations of the jet base in nearby radio galaxy M87, obtained by Very Long Baseline Array conjunction with Green Bank Telescope. The resulting image has a dynamic range exceeding 1500 to 1, highest ever achieved for this at frequency, resolving and imaging detailed formation/collimation structure down ~10 Schwarzschild radii (Rs). clearly confirms some important features known lower frequencies, i.e.,...
Abstract We propose a new imaging technique for radio and optical/infrared interferometry. The proposed reconstructs the image from visibility amplitude closure phase, which are standard data products of short-millimeter very long baseline interferometers such as Event Horizon Telescope (EHT) interferometers, by utilizing two regularization functions: ℓ 1 -norm total variation (TV) brightness distribution. In method, optimal parameters, represent sparseness effective spatial resolution...
Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order ∼0.1c in a limited sample six broad-line radio galaxies. They are observed as blueshifted Fe xxv–xxvi K-shell absorption lines, similarly ultrafast outflows (UFOs) reported Seyferts and quasars. In this work we extend search for such K lines larger 26 radio-loud active galactic nuclei (AGN) XMM–Newton Suzaku. The is drawn from Swift Burst Alert Telescope 58-month catalogue blazars...
Abstract We propose a new technique for radio interferometry to obtain superresolution full-polarization images in all four Stokes parameters using sparse modeling. The proposed reconstructs the image each parameter from corresponding full-complex visibilities by utilizing two regularization functions: ℓ 1 norm and total variation (TV) of brightness distribution. As an application this technique, we present simulated linear polarization observations physically motivated models M87 with Event...
We present the first astrometry catalog from Japanese VLBI (very long baseline interferometer) project VERA (VLBI Exploration of Radio Astrometry). have compiled all results VERA, providing accurate trigonometric annual parallax and proper motion measurements. In total, 99 maser sources are listed in catalog. Among them, 21 newly reported while rest 78 referred to previously published or those preparation for forthcoming papers. The accuracy revisited compared with other projects such as...
We report measurements of the gravitationally lensed secondary image -- first in an infinite series so-called "photon rings" around supermassive black hole M87* via simultaneous modeling and imaging 2017 Event Horizon Telescope (EHT) observations. The inferred ring size remains constant across seven days EHT observing campaign is consistent with theoretical expectations, providing clear evidence that such probe spacetime a striking confirmation models underlying set results. residual diffuse...
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...
Abstract The M87 jet is extensively examined by utilizing general relativistic magnetohydrodynamic (GRMHD) simulations, as well the steady axisymmetric force-free electrodynamic (FFE) solution. Quasi-steady funnel jets are obtained in GRMHD simulations up to scale of ∼100 gravitational radii ( r g ) for various black hole (BH) spins. As known, edge approximately determined following equipartitions: (i) magnetic and rest-mass energy densities (ii) gas pressures. Our numerical results give an...
X-ray and near-infrared ($J$-$H$-$K_{\rm s}$) observations of the Galactic black hole binary GX 339--4 in low/hard state were performed with Suzaku IRSF 2009 March. The spectrum 0.5--300 keV band is dominated by thermal Comptonization multicolor disk photons, a small contribution from direct component, indicating that inner almost fully covered hot corona an electron temperature $\approx$175 keV. Comptonizing has at least two optical depths, $\tau \approx 1,0.4$. Analysis iron-K line profile...
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...
Abstract We propose a new imaging technique for interferometry using sparse modeling, utilizing two regularization terms: the ℓ 1 -norm and function named total squared variation (TSV) of brightness distribution. First, we demonstrate that our may achieve superresolution ∼30% compared with traditional CLEAN beam size synthetic observations point sources. Second, present simulated three physically motivated static models Sgr A* Event Horizon Telescope (EHT) to show performance proposed...
ABSTRACT We report the results obtained by a systematic, broadband (0.5–150 keV) X-ray spectral analysis of moderately obscured (Compton-thin, <?CDATA $22\leqslant \mathrm{log}{N}_{{\rm{H}}}\lt 24$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>22</mml:mn> <mml:mo>≤</mml:mo> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:msub> <mml:mo><</mml:mo> <mml:mn>24</mml:mn> </mml:math> )...
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...
Context. Because of its proximity and the large size black hole, M 87 is one best targets for studying launching mechanism active galactic nucleus jets. Currently, magnetic fields are considered to be an essential factor in accelerating jet. However, current observational estimates field strength jet limited innermost part (≲100 r s ) or HST-1 (∼10 5 ). No attempt has yet been made measure between. Aims. We aim infer out a distance several thousand by tracking distance-dependent changes...
ABSTRACT We systematically analyze the broadband (0.5–200 keV) X-ray spectra of hard (>10 selected local low-luminosity active galactic nuclei (LLAGNs) observed with Suzaku and Swift /BAT. The sample consists 10 LLAGNs detected /BAT intrinsic 14–195 keV luminosities smaller than 42 erg s −1 available in archive, covering a wide range Eddington ratio from −5 to −2 . overall can be reproduced an absorbed cut-off power law, often accompanied by reflection components distant cold matter,...
The collimation of relativistic jets launched from the vicinity supermassive black holes (SMBHs) at centers active galactic nuclei (AGN) is one key questions to understand nature AGN jets. However, little known about detailed jet structure for like quasars since very high angular resolutions are required resolve these objects. We present long baseline interferometry (VLBI) observations archetypical quasar 3C 273 86 GHz, performed with Global Millimeter VLBI Array, first time including...
We report the first broadband X-ray spectra of low-luminosity active galactic nuclei (LLAGNs), NGC 1566 (type 1.5) and 4941 2), observed with Suzaku Swift/BAT covering 0.5–195 keV band. Both targets have hard luminosities ∼1041–42 erg s−1 in 15–55 The nucleus are well reproduced by a sum partially or fully covered transmitted emission its reflection from accretion disk, reprocessed torus accompanied strong narrow iron-Kα line, scattered component (for 4941). do not significantly detect broad...
Recent VLBI monitoring has found transverse motions of the M87 jet. However, due to limited cadence previous observations, details motion have not been fully revealed yet. We regularly monitored jet at KVN and VERA Array (KaVA) 22 GHz from December 2013 June 2016. The average time interval observation is ∼0.1 year, which suitable for tracking short-term structural changes. From these well represented by double ridge lines in region 2–12 mas core. that exhibit oscillations all observed...
We report the results of Suzaku broadband X-ray observations two narrow-line radio galaxies, 3C 403 and IC 5063. Combined with Swift/Burst Alert Telescope (BAT) spectra averaged for 58 months, we are able to accurately constrain their spectral properties over 0.5–200 keV band. The both nuclei well represented an absorbed cutoff power law, reflection component from cold matter iron–K emission line, unabsorbed soft component, which gives a firm upper limit scattered emission. strength...
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...
We present the results from broad-band X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku Swift/BAT, two most luminous unobscured obscured radio-loud active galactic nuclei hard luminosities 10^{45.5} erg s^{-1} 10^{44.9} (14--195 keV), respectively. Based on radio core luminosity, we estimate that spectrum contains a significant (~ 60% in 14--195 keV band) contribution jet, while it is negligible 0707-35. can successfully model spectra jet component (for 206), transmitted...
IRAS 00521$-$7054 is the first Seyfert 2 in which presence of an extremely large Fe K$\alpha$ line has been claimed. We report here on analysis a 100 ks Suzaku observation source. confirm existence very strong excess over power-law X-ray continuum at $E\sim6$ keV ($EW\simeq 800$ eV), extending down to $\sim 4.5$ keV, and found that spectrum source can be explained by two different models. i) An absorption scenario, obscured fully-covering ionized absorbers, with reflection component from...
We introduce a new imaging method for radio interferometry based on sparse- modeling. The direct observables in are visibilities, which Fourier transformation of an astronomical image the sky-plane, and incomplete sampling visibilities spatial frequency domain results under-determined problem, has been usually solved with 0 filling to un-sampled grids. In this paper we propose directly solve problem using sparse modeling without filling, realizes super resolution, i.e., resolution higher...