Atsushi Miyazaki

Hosei University, Edo, Tokyo, Japan

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Publications (87)166.78 Total impact

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    ABSTRACT: The Interferometric Monitoring of Gamma-ray Bright Active galactic nuclei (iMOGABA) program provides not only simultaneous multifrequency observations of bright gamma-ray detected active galactic nuclei (AGN), but also covers the highest Very Large Baseline Interferometry (VLBI) frequencies ever being systematically monitored, up to 129 GHz. However, observation and imaging of weak sources at the highest observed frequencies is very challenging. In the second paper in this series, we evaluate the viability of the frequency phase transfer technique to iMOGABA in order to obtain larger coherence time at the higher frequencies of this program (86 and 129 GHz) and image additional sources that were not detected using standard techniques. We find that this method is applicable to the iMOGABA program even under non-optimal weather conditions.
    Full-text · Article · Oct 2015 · Journal of the Korean Astronomical Society
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    Masato Tsuboi · Atsushi Miyazaki · Kenta Uehara
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    ABSTRACT: We performed a search of star-forming sites influenced by external factors, such as SNRs, H ii regions, and cloud–cloud collisions (CCCs), to understand the star-forming activity in the Galactic center region using the NRO Galactic Center Survey in SiO v = 0, J = 2–1, H13CO+J = 1–0, and CS J = 1–0 emission lines obtained with the Nobeyama 45 m telescope. We found a half-shell-like feature (HSF) with a high integrated line intensity ratio of ∫TB(SiO v = 0, J = 2–1)dv/∫TB(H13CO+J = 1–0)dv ∼ 6–8 in the 50 km s−1 molecular cloud; the HSF is a most conspicuous molecular cloud in the region and harbors an active star-forming site where several compact H ii regions can be seen. The high ratio in the HSF indicates that the cloud contains huge shocked molecular gas. The HSF can be also seen as a half-shell feature in the position–velocity diagram. A hypothesis explaining the chemical and kinetic properties of the HSF is that the feature originates from a CCC. We analyzed the CS J = 1–0 emission line data obtained with the Nobeyama Millimeter Array to reveal the relation between the HSF and the molecular cloud cores in the cloud. We made a cumulative core mass function (CMF) of the molecular cloud cores within the HSF. The CMF in the CCC region is not truncated at least up to ∼2500 M⊙, although the CMF of the non-CCC region reaches the upper limit of ∼1500 M⊙. Most massive molecular cores with Mgas > 750 M⊙ are located only around the ridge of the HSF and adjoin the compact H ii region. These may be a sign of massive star formation induced by CCCs in the Galactic center region.
    Preview · Article · Jul 2015 · Publications- Astronomical Society of Japan
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    Masato Tsuboi · Atsushi Miyazaki · Kenta Uehara
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    ABSTRACT: We present results from a high-resolution wide-field imaging observation of the Central Molecular Zone (CMZ) in H13CO+ J = 1–0 and SiO v = 0, J = 2–1 emission lines using the 45-m telescope at the Nobeyama Radio Observatory in order to depict the high-density molecular gas mass distribution and explore molecular gas affected by interstellar shocks. By using the clumpfind algorithm we identify 114 molecular clumps in the H13CO+ data cube. The clump mass function (CMF) can be described by a power law (dN/dM ∝ M−γ, with γ ≃ 2) in the range of 5 × 103 < Mclump < 2 × 104 M⊙. The brightness temperature ratio RT = T(SiO)/T(H13CO+) indicates the strength of the shock. The Sgr B2 complex has several expanding shell-like structures with a large velocity-width (ΔV > 50 km s−1). They correspond to the high brightness temperature ratio area (RT ≲ 8). A Large Velocity Gradient model analysis with the RADEX program confirms the enhancement of SiO molecules in the shells. On the other hand, there is no such large shell with a high ratio in the Sgr A complex. A hollow hemispherical structure is found in the l–b–v data cube of the Sgr B2 complex. The central part of the structure has a high ratio (RT ≲ 8). The ratio decreases with proximity to the outer area. The properties are consistent with those expected from simulations of cloud–cloud collisions. The structure is probably a site of ongoing cloud–cloud collision.
    Preview · Article · Jul 2015 · Publications- Astronomical Society of Japan
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    Masato Tsuboi · Atsushi Miyazaki · Toshihiro Handa
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    ABSTRACT: We present results from a high-resolution wide-field imaging observation of the central molecular zone (CMZ) in H13CO+ J = (1 − 0) and SiO v=0, J = (2−1) emission lines by using the Nobeyama 45-m telescope in order to depict the high-density molecular gas mass distribution and explore molecular gas affected by interstellar shocks. We found a candidate for ongoing cloud-cloud collision in the Sgr B2 complex. This is identified as a hollow paraboloid-like structure in the l−b−v data cube of both emission lines. The central part of the feature is denser and warmer than the outer envelope and contains a vast amount of shocked molecular gas. These properties are consistent with those expected from simulations of cloud-cloud collisions in the CMZ.
    Preview · Article · Oct 2014 · Proceedings of the International Astronomical Union
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    A. Miyazaki · S. S. Lee · B. W. Sohn · T. Jung · M. Tsuboi · T. Tsutsumi
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    ABSTRACT: We searched the time lag between the intra-day variables (IDVs) of Sagittarius A* at 22, 43, and 86 GHz bands using the Korean VLBI Network (KVN). The time lags between the IDV flare peaks at 22 and 43 GHz are reported, and they suggest that the flare emissions come from adiabatically expanding plasma blobs, ejected close to the Galactic center black hole. We searched the time lags between light curves at 90 and 102 GHz using the Nobeyama Millimeter Array, but could not find significant time lags. In order to detect the diversity of the time lags of Sgr A* flares, we performed observations of Sgr A* in the 22, 43, and 86 GHz bands using the KVN in the winter of 2013. Because the receiver system of KVN can observe Sgr A* in these three bands simultaneously, the KVN is very useful to detect the time lags of Sgr A* flares.
    Preview · Article · Oct 2014 · Proceedings of the International Astronomical Union
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    T. Tsutsumi · A. Miyazaki · M. Tsuboi
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    ABSTRACT: We present the analysis of flux variations of Sgr A* at millimeter wavelengths based on the long-term monitoring project spanning over a decade using the Nobeyama Millimeter Array. We investigate basic characteristics of the flux variability using some standard parameterizations of the data. Such basic properties of the flux variations in the mm-regime can provide valuable information not only for its underlying mechanisms in general but also for understanding observed radio/mm flux measurements during an accretion event.
    Preview · Article · Oct 2014 · Proceedings of the International Astronomical Union
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    ABSTRACT: The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23–43 GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M 87. This is one of the initial results of KaVA's early operation. Our KaVA images reveal extended outflows with complex substructures such as knots and limb brightening, in agreement with previous Very Long Baseline Array (VLBA) observations. Angular resolutions are better than 1.4 and 0.8 mas at 23 and 43 GHz, respectively. KaVA achieves a high dynamic range of ∼ 1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN outflows, at least comparable to the best existing radio interferometric arrays.
    Full-text · Article · Jun 2014 · Publications- Astronomical Society of Japan
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    ABSTRACT: We have carried out the first very long baseline interferometry (VLBI) imaging of a 44 GHz class I methanol maser (70-61A +) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151–1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds × 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than ≈ 650 km corresponding to 100 Mλ in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~5 mas × 2 mas, which corresponds to the linear size of ~15 AU × 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ~3.5 × 108 to 1.0 × 1010 K, which are higher than the estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ~50 mas. The 44 GHz class I methanol maser in IRAS 18151–1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.
    Full-text · Article · Jun 2014 · The Astrophysical Journal Letters
  • M. Tsuboi · M. T. Sato · K.-I. Tadaki · A. Miyazaki · T. Handa
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    ABSTRACT: We identified a large expanding shell in the southeastern extension of the Sgr B2 complex using a survey observation of the CMZ in SiO v = 0, J = 2-1 and H13CO+ J = 1-0 emission lines by the Nobeyama 45-m telescope. The shell has high brightness temperature ratio of TB(SiO) /TB(H13CO+) = 6-8 and wide velocity width of Δ V ≥ 70 km s-1. This structure was presumably originated by successive super novae or an extreme super nova exploded within 5 × 105 yrs.
    No preview · Article · Oct 2013
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    Atsushi Miyazaki · Masato Tsuboi · Takahiro Tsutsumi
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    ABSTRACT: We performed observations of the flux densities of Sgr A$ ^\star$ at 90 and 102 GHz in order to detect any time lag between these frequencies using the Nobeyama Millimeter Array, which was previously reported at lower frequencies. We detected a radio flare during the observation period on 2005 April 6, and calculated the z-transformed discrete correlation function between the light curves. No time lag between these frequencies was detected. If the expanding plasma model, which explains a time lag at lower frequencies, is valid, the light curve at 90 GHz would be delayed in respect to that at 102 GHz. This result suggests that plasma blobs ejected close to the Galactic center black hole may be widely diverse, especially in optical thickness. Another possibility is that a major portion of the flux above 100 GHz does not originate in blobs.
    Preview · Article · Jun 2013 · Publications- Astronomical Society of Japan
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    Atsushi Miyazaki · Masato Tsuboi · Takahiro Tsutsumi
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    ABSTRACT: We performed the observation of the flux densities of SgrA* at 90 and 102GHz in order to detect the time lag between these frequencies using the Nobeyama Millimeter Array, which was previously reported at lower frequencies. We detected a radio flare during the observation period on 6 April 2005 and calculated the z-transformed discrete correlation function between the light curves. The time lag between these frequencies was not detected. If the expanding plasma model which explains the time lag at lower frequencies is valid, the light curve at 90GHz would be delayed with respect to the one at 102GHz. This result suggests that the plasma blobs ejected near the Galactic Center black hole may be widely diverse especially in optical thickness. Another possibility is that the major portion of the flux above 100GHz does not originate from the blobs.
    Full-text · Article · Apr 2013 · Publications- Astronomical Society of Japan
  • Masato Tsuboi · Atsushi Miyazaki
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    ABSTRACT: We present the statistical properties of molecular clumps in the Galactic center 50 km s-1 molecular cloud based on observations of the CS J = 1 - 0 emission line with the Nobeyama Millimeter Array. The CMF and size spectrum for the whole cloud can be described by power laws of dN/dM ∝ M-2.6 ± 0.1 and dN/dR ∝ R-5.9±0.3, respectively. The CMF observed in the interacting part with the Sgr A East steepens to dN/dM ∝ M -4.0±0.2. On the other hand, the interaction presumably truncates the size spectrum on the larger side of R ˜ 0.4 pc.
    No preview · Article · Mar 2013 · Proceedings of the International Astronomical Union
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    Atsushi Miyazaki · Masato Tsuboi · Takahiro Tsutsumi
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    ABSTRACT: We performed the observation of the flux densities of Sgr A* at 90 and 102 GHz on 6 April 2005 using the Nobeyama Millimeter Array in order to detect the time lag between these frequencies. We constructed light curves covering a few hour with 1 min bin, and the Intra-Day Variability, which had a rising phase and intensity peak, of Sgr A* is clearly seen at both frequencies. We calculated the z-transformed discrete correlation function between the light curves of Sgr A* at 90 and 102 GHz. The derived time lag of the flares at these frequencies was approximately zero, contrary to our expectations based on the previously reported time lag at lower frequencies. If the radio flares of Sgr A* are explained by the expanding plasma model, the light curve at 90 GHz would be delayed with respect to the one at 102 GHz. However, we could not find such a delay with statistical significance in our data.
    Full-text · Article · Nov 2012 · Proceedings of the International Astronomical Union
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    Masato Tsuboi · K.-i. Tadaki · Atsushi Miyazaki · Toshihiro Handa
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    ABSTRACT: We present results of a high-resolution wide-field mapping observation of the Sagittarius A (Sgr A) molecular cloud complex in (HCO+)-C-13 J = 1-0 and thermal SiO J = 2-1 emission lines with the 25-beam receiver of the 100 GHz band operating on the Nobeyama Radio Observatory 45-m telescope. The mapping area covers a 0 degrees 5 x 0 degrees 5 area involving several named molecular clouds, for example GCM -0.02-0.07, GCM -0.13-0.08, GCM 0.11-0.11, the Sickle molecular cloud, the Arched filaments molecular cloud, and so on. The data have an effective angular resolution of 26 ''. The (HCO+)-C-13 emission line is a famous tracer of molecular gas mass because the line is optically thin, even in the Galactic center region, and is not emphasized by shock. The emission line presents a clumpy distribution of the molecular cloud. The averaged fractional abundance in the Sgr A complex is N((HCO+)-C-13)/N-H2 similar or equal to (1.8 +/- 0.4) x 10(-11), comparing the LTE mass and the virial theorem mass. The SiO emission line is a famous and reliable tracer of shocked molecular gas. We find many molecular clouds that are remarkable only in the SiO emission line. Such molecular clouds have a large velocity width of up to 60 km s(-1). The brightness temperature ratio is up to TB(SiO)/TB((HCO+)-C-13) less than or similar to 8. The features are dominated by shock SiO-enriched gas. In such clouds, the ratio of the fractional abundance of SiO and (HCO+)-C-13 molecules is X (SiO)/ X ((HCO+)-C-13) similar to 100. The features are presumably made by supernova remnants. We found a prototypical example in GCM -0.02-0.07. It has two distinct structures. One is a ridge-like structure contacting with the Sgr A East shell; another is an expanding shell-like structure. There is a wide-velocity width ridge of SiO-enriched gas in GCM 0.11-0.11, which is adjacent to Vertical filaments. This suggests that the collision with the molecular cloud accelerates relativistic electrons, which, illuminate the Vertical filaments-Polarized Plumes complex.
    Preview · Article · Jun 2012 · Publications- Astronomical Society of Japan
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    Masato Tsuboi · Atsushi Miyazaki
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    ABSTRACT: We present the statistical properties of molecular clumps in the Galactic center 50 km s$ ^{-1}$ molecular cloud (GCM-0.02-0.07) based on observations of the CS $ J$ $ =$ 1–0 emission line with the Nobeyama Millimeter Array. In the cloud, 37 molecular clumps with local thermodynamic equilibrium (LTE) masses of 2 $ \times$ 10$ ^{2}$ –6 $ \times$ 10$ ^{3}\ M_{\odot}$ were identified by using the clumpfind algorithm. The velocity widths of the molecular clumps are about five-fold those of Galactic disk molecular clouds with the same radius. The virial-theorem masses are three-fold the LTE masses. The mass and size spectra can be described by power laws of $ dN/dM$ $ \propto$ $ M^{-2.6\pm0.1}$ ($ M$ $ \gtrsim$ 900 $ M_{\odot}$ ) and $ dN/dR$ $ \propto$ $ R^{-5.9\pm0.3}$ ($ R$ $ \gtrsim$ 0.35 pc), respectively. The statistical properties of the region interacting with the Sgr A East shell and those of the non-interacting part of the cloud are significantly different. The interaction probably makes the mass function steeper, from $ dN/dM$ $ \propto$ $ M^{-2.0\pm0.1}$ in the non-interacting part to $ dN/dM$ $ \propto$ $ M^{-4.0\pm0.2}$ in the interacting region. On the other hand, the interaction presumably truncates the size spectrum on the larger side of $ R$ $ \sim$ 0.4 pc.
    Full-text · Article · Apr 2012 · Publications- Astronomical Society of Japan
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    ABSTRACT: A new high-speed Data Acquisition System (DAS) has been developed for the millimeter-wave VLBI array newly constructed in Korea, the Korean VLBI Network (KVN). The KVN DAS is specially designed to support the most distinctive feature of the KVN, that is simultaneous reception of multiple frequency bands (22, 43, 86 and 129-GHz bands in the current KVN system) for realizing multi-frequency phase referencing, which is the key technology for successful millimeter-wave VLBI observations toward active galactic nuclei and astronomical maser sources. Although the basic functions of the KVN DAS succeed technological elements originally developed in the VERA (VLBI Exploration of Radio Astrometry) Project, essentially new designs have been introduced for the simultaneous processing of four data streams in the optical data-transmission system, the digital filter, and the digital spectrometer. The KVN DAS system consists of four Gigabit Samplers (GBS), Optical Transmission System (OTS), Digital Filter Bank (DFB), Digital Spectrometer (DSM), and the data recorder. The DFB realizes very flexible and phase-stable channelization of up to four data streams. The DSM facilitates quick look of power and cross-power spectra of observed data. The VLBI output data from the DFB are recorded to the Mark5B recorder with a maximum rate of 1-Gbps. We discuss in the present paper the primary specifications, designs, and experimental results of the KVN DAS system.
    Full-text · Article · Nov 2011 · Publications- Astronomical Society of Japan
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    ABSTRACT: Cygnus X-3 (Cyg X-3) is a well-known microquasar with relativistic jets. It is especially famous for its giant radio outbursts, which have been observed once every few years since their first discovery. Each giant outburst presumably consists of a series of short-duration flares. The physical parameters of the flares in the giant outbursts are difficult to derive because the successive flares overlap. Here, we report on isolated flares in the quiescent phase of Cyg X-3, as observed at 23, 43, and 86 GHz with the 45-m radio telescope at Nobeyama Radio Observatory. The observed flares have small amplitude (0.5–2 Jy) and short duration (1–2 hr). The millimeter fluxes rapidly increase, and then exponentially decay. The lifetime of the decay is shorter at higher frequency. The radio spectrum of Cyg X-3 during the flares is flat or inverted around the peak flux density. After that, the spectrum gradually becomes steeper. The observed characteristics are consistent with those of an adiabatic expanding plasma. The brightness temperature of the plasma at the peak is estimated to be $T_{\rm B}$ $\gtrsim$ 1 $\times$ 10$^{11}\ $K. The magnetic field in the plasma is calculated to be 0.2 $\lesssim$ $H$ $\lesssim$ 30 G.
    Full-text · Article · Sep 2011 · Publications- Astronomical Society of Japan
  • M. Tsuboi · K.-I. Tadaki · A. Miyazaki · T. Handa
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    ABSTRACT: We present results of a high-resolution wide-field mapping observation of the Sagittarius A (Sgr A) molecular cloud complex in H 13CO + J = 1-0 and thermal SiO J = 2-1 emission lines with the 25-beam receiver of the 100GHz band operating on the Nobeyama Radio Observatory 45-m telescope. The mapping area covers a 0.°5 × 0. °5 area involving several named molecular clouds, for example GCM -0.02-0.07, GCM -0.13-0.08, GCM 0.11-0.11, the Sickle molecular cloud, the Arched filaments molecular cloud, and so on. The data have an effective angular resolution of 26″. The H 13CO + emission line is a famous tracer of molecular gas mass because the line is optically thin, even in the Galactic center region, and is not emphasized by shock. The emission line presents a clumpy distribution of the molecular cloud. The averaged fractional abundance in the Sgr A complex is N(H 13CO +)=NH 2 ≃ (1.8±0.4) × 10 -11, comparing the LTE mass and the virial theorem mass. The SiO emission line is a famous and reliable tracer of shocked molecular gas. We find many molecular clouds that are remarkable only in the SiO emission line. Such molecular clouds have a large velocity width of up to 60 kms -1. The brightness temperature ratio is up to T B (SiO)=T B (H 13CO +) ≲ 8. The features are dominated by shock SiO-enriched gas. In such clouds, the ratio of the fractional abundance of SiO and H 13CO + molecules is X(SiO)=X(H 13CO +) ∼ 100. The features are presumably made by supernova remnants. We found a prototypical example in GCM -0.02-0.07. It has two distinct structures. One is a ridge-like structure contacting with the Sgr A East shell; another is an expanding shell-like structure. There is a wide-velocity width ridge of SiO-enriched gas in GCM 0.11-0.11, which is adjacent to Vertical filaments. This suggests that the collision with the molecular cloud accelerates relativistic electrons, which illuminate the Vertical filaments-Polarized Plumes complex.
    No preview · Article · Aug 2011 · Publications- Astronomical Society of Japan
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    Masato Tsuboi · Ken-Ichi Tadaki · Atsushi Miyazaki · Toshihiro Handa
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    ABSTRACT: We present results of a high-resolution wide-field mapping observation of the Sagittarius A (Sgr A) molecular cloud complex in H$^{13}$CO$^+$ $J$ $=$ 1–0 and thermal SiO $J$ $=$ 2–1 emission lines with the 25-beam receiver of the 100 GHz band operating on the Nobeyama Radio Observatory 45-m telescope. The mapping area covers a 0$^\circ\!\!\!.$5 $\times$ 0$^\circ\!\!\!.$5 area involving several named molecular clouds, for example GCM$-$0.02$-$0.07, GCM$-$0.13$-$0.08, GCM 0.11$-$0.11, the Sickle molecular cloud, the Arched filaments molecular cloud, and so on. The data have an effective angular resolution of 26$''$. The H$^{13}$CO$^+$ emission line is a famous tracer of molecular gas mass because the line is optically thin, even in the Galactic center region, and is not emphasized by shock. The emission line presents a clumpy distribution of the molecular cloud. The averaged fractional abundance in the Sgr A complex is $N$(H$^{13}$CO$^+$)$/N_{\mathrm{H_2}}$ $\simeq$ (1.8$\ \pm\ $0.4) $\times$ 10$^{-11}$, comparing the LTE mass and the virial theorem mass. The SiO emission line is a famous and reliable tracer of shocked molecular gas. We find many molecular clouds that are remarkable only in the SiO emission line. Such molecular clouds have a large velocity width of up to 60 km s$^{-1}$. The brightness temperature ratio is up to $T_{\mathrm{B}}$(SiO)$/T_{\mathrm{B}}$(H$^{13}$CO$^+$) $\lesssim$ 8. The features are dominated by shock SiO-enriched gas. In such clouds, the ratio of the fractional abundance of SiO and H$^{13}$CO$^+$ molecules is $X$(SiO)$/X$(H$^{13}$CO$^+$) $\sim$ 100. The features are presumably made by supernova remnants. We found a prototypical example in GCM$-$0.02$-$0.07. It has two distinct structures. One is a ridge-like structure contacting with the Sgr A East shell; another is an expanding shell-like structure. There is a wide-velocity width ridge of SiO-enriched gas in GCM 0.11$-$0.11, which is adjacent to Vertical filaments. This suggests that the collision with the molecular cloud accelerates relativistic electrons, which illuminate the Vertical filaments–Polarized Plumes complex.
    Preview · Article · Aug 2011 · Publications- Astronomical Society of Japan
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    ABSTRACT: This paper reviews the recent progress in the study of the intra-day variability (IDV) of Sagitarrius A* (Sgr A*), the best known supermassive black hole candidates with a dark mass concentration of 4 × 10 6 M\odot^6 M_{\odot} at the center of our galaxy. KeywordsGalaxy–center—galaxies–individual (Sagittarius A*)—techniques–interferometric
    Full-text · Article · Jun 2011 · Journal of Astrophysics and Astronomy

Publication Stats

741 Citations
166.78 Total Impact Points

Institutions

  • 2015
    • Hosei University
      • Department of Applied Informatics
      Edo, Tokyo, Japan
  • 2011-2014
    • Korea Astronomy and Space Science Institute
      Daiden, Daejeon, South Korea
  • 2012
    • Yonsei University
      Sŏul, Seoul, South Korea
  • 2003-2011
    • National Astronomical Observatory of Japan
      • • Astronomy Data Center
      • • Mizusawa VLBI Observatory
      Edo, Tōkyō, Japan
  • 2008
    • University of Melbourne
      • School of Physics
      Melbourne, Victoria, Australia
  • 2003-2008
    • National Institutes Of Natural Sciences
      Edo, Tōkyō, Japan
  • 1998-2008
    • Ibaraki University
      Mito-shi, Ibaraki, Japan
  • 2006-2007
    • Chinese Academy of Sciences
      • Shanghai Astronomical Observatory
      Peping, Beijing, China
    • Nanjing University
      • Department of Astronomy
      Nan-ching, Jiangsu Sheng, China
  • 2005
    • The University of Manchester
      • Jodrell Bank Centre for Astrophysics
      Manchester, England, United Kingdom