Updated on 2022/10/31

写真a

 
WADA KEIICHI
 
Organization
Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Department of Science Physics and Astronomy Program Professor
Title
Professor

Degree

  • 博士(理学) ( 1993.12   北海道大学 )

  • 修士(理学) ( 1991.3   北海道大学 )

Research Interests

  • 数値計算

  • 星間ガス

  • 銀河

  • 銀河、活動銀河核、理論天文学

Research Areas

  • Natural Science / Astronomy  / 銀河、活動銀河核、ブラックホール

Education

  • Hokkaido University

    - 1993.12

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    Country: Japan

  • Tohoku University

    - 1989.3

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    Country: Japan

Research History

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Department of Science Physics and Astronomy Program   Professor

    2020.4

  • Kagoshima University   Professor

    2009.8

  • Kagoshima University   Research Field in Science, Science and Engineering Area Graduate School of Science and Engineering (Science) Physics and Astronomy Course   Professor

    2009.8 - 2020.3

  • 自然科学研究機構国立天文台   理論研究部   准教授

    2004.4 - 2009.7

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    Country:Japan

  • 国立天文台   位置天文・天体力学研究系   准教授

    2004.1 - 2004.3

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    Country:Japan

  • 国立天文台   理論天文学研究系   助手

    1997.5 - 2003.12

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    Country:Japan

  • Hokkaido University   Research Assistant

    1994.1 - 1997.5

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    Country:Japan

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Professional Memberships

  • 国際天文学連合

    2015.10

  • 日本物理学会

    2015.10

  • 日本天文学会

    1991.4

Studying abroad experiences

  • 2000.8 - 2001.6   University of Colorado   Visiting Professor

  • 1998.8 - 1998.12   Johns Hopkins University   Associate Research Scientist

  • 1997.9 - 1998.7   Space Telescope Science Institute   Visiting Scholar

 

Papers

  • Kosei Matsumoto, Takao Nakagawa, Keiichi Wada, Shunsuke Baba, Shusuke Onishi, Taisei Uzuo, Naoki Isobe, Yuki Kudoh .  Probing Dynamics and Thermal Properties Inside Molecular Tori with CO Rovibrational Absorption Lines .  The Astrophysical Journal934 ( 1 ) 25 - 39   2022.7Reviewed

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    Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    Abstract

    A recent hydrodynamic model, the radiation-driven fountain model (Wada et al. 2016), presented a dynamical picture that active galactic nuclei (AGNs) tori sustain their geometrical thickness by gas circulation around AGNs, and previous papers have confirmed that this picture is consistent with multiwavelength observations of nearby Seyfert galaxies. Recent near-infrared observations implied that CO rovibrational absorption lines (ΔJ = ± 1, v = 0 − 1, λ ∼ 4.7 μm) could probe the physical properties of the inside tori. However, the origin of the CO absorption lines has been under debate. In this paper, we investigate the origin of the absorption lines and conditions for detecting them by performing line radiative transfer calculations based on the radiation-driven fountain model. We find that CO rovibrational absorption lines are detected at inclination angles θ<sub>obs</sub> = 50°–80°. At the inclination angle θ<sub>obs</sub> = 77°, we observe multi-velocity components: inflow (v<sub>LOS</sub> = 30 km s<sup>−1</sup>), systemic (v<sub>LOS</sub> = 0 km s<sup>−1</sup>), and outflows (v<sub>LOS</sub> = −75, − 95, and −105 km s<sup>−1</sup>). The inflow and outflow components (v<sub>LOS</sub> = 30 and −95 km s<sup>−1</sup>) are collisionally excited at the excitation temperatures of 186 and 380 K up to J = 12 and 4, respectively. The inflow and outflow components originate from the accreting gas on the equatorial plane at 1.5 pc from the AGN center and the outflowing gas driven by AGN radiation pressure at 1.0 pc, respectively. These results suggest that CO rovibrational absorption lines can provide us with the velocities and kinetic temperatures of the inflow and outflow in the inner few parsec region of AGN tori, and the observations can probe the gas circulation inside the tori.

    DOI: 10.3847/1538-4357/ac755f

    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac755f/pdf

  • Yoshiki Toba, Teng Liu, Tanya Urrutia, Mara Salvato, Junyao Li, Yoshihiro Ueda, Marcella Brusa, Naomichi Yutani, Keiichi Wada, Atsushi J. Nishizawa, Johannes Buchner, Tohru Nagao, Andrea Merloni, Masayuki Akiyama, Riccardo Arcodia, Bau-Ching Hsieh, Kohei Ichikawa, Masatoshi Imanishi, Kaiki T. Inoue, Toshihiro Kawaguchi, Georg Lamer, Kirpal Nandra, John D. Silverman, Yuichi Terashima .  The eROSITA Final Equatorial-Depth Survey (eFEDS) A multiwavelength view of WISE mid-infrared galaxies/active galactic nuclei .  ASTRONOMY & ASTROPHYSICS661   2022.5The eROSITA Final Equatorial-Depth Survey (eFEDS) A multiwavelength view of WISE mid-infrared galaxies/active galactic nuclei

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:EDP SCIENCES S A  

    Aims. We investigate the physical properties - such as the stellar mass (M-*), star-formation rate, infrared (IR) luminosity (L-IR), X-ray luminosity (L-X), and hydrogen column density (N-H) - of mid-IR (MIR) galaxies and active galactic nuclei (AGN) at z < 4 in the 140 deg(2) field observed by eROSITA on SRG using the Performance-and-Verification-Phase program named the eROSITA Final Equatorial Depth Survey (eFEDS).Methods. By cross-matching the WISE 22 mu m (W4)-detected sample and the eFEDS X-ray point-source catalog, we find that 692 extragalactic objects are detected by eROSITA. We have compiled a multiwavelength dataset extending from X-ray to far-IR wavelengths. We have also performed (i) an X-ray spectral analysis, (ii) spectral-energy-distribution fitting using X-CIGALE, (iii) 2D image-decomposition analysis using Subaru Hyper Suprime-Cam images, and (iv) optical spectral fitting with QSFit to investigate the AGN and host-galaxy properties. For 7088 WISE 22 tim objects that are undetected by eROSITA, we have performed an X-ray stacking analysis to examine the typical physical properties of these X-ray faint and probably obscured objects.Results. We find that (i) 82% of the eFEDS-W4 sources are classified as X-ray AGN with log L-X > 42 erg s(-1); (ii) 67 and 24% of the objects have log (L-IR/L-circle dot) > 12 and 13, respectively; (iii) the relationship between L-X and the 6 mu m luminosity is consistent with that reported in previous works; and (iv) the relationship between the Eddington ratio and N-H for the eFEDS-W4 sample and a comparison with a model prediction from a galaxy-merger simulation indicates that approximately 5.0% of the eFEDS-W4 sources in our sample are likely to be in an AGN-feedback phase, in which strong radiation pressure from the AGN blows out the surrounding material from the nuclear region.Conclusions. Thanks to the wide area coverage of eFEDS, we have been able to constrain the ranges of the physical properties of the WISE 22 mu m-selected sample of AGNs at z < 4, providing a benchmark for forthcoming studies on a complete census of MIR galaxies selected from the full-depth eROSITA all-sky survey.

    DOI: 10.1051/0004-6361/202141547

    Web of Science

  • Shinsuke Takasao, Yuri Shuto, Keiichi Wada .  Spontaneous Formation of Outflows Powered by Rotating Magnetized Accretion Flows in a Galactic Center .  The Astrophysical Journal926 ( 1 ) 50 - 50   2022.2Reviewed

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    Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    <title>Abstract</title>
    We investigate how magnetically driven outflows are powered by a rotating, weakly magnetized accretion flow onto a supermassive black hole using axisymmetric magnetohydrodynamic simulations. Our proposed model focuses on the accretion dynamics on an intermediate scale between the Schwarzschild radius and the galactic scale, which is ∼1–100 pc. We demonstrate that a rotating disk formed on a parsec-scale acquires poloidal magnetic fields via accretion, and this produces an asymmetric bipolar outflow at some point. The formation of the outflow was found to follow the growth of strongly magnetized regions around disk surfaces (magnetic bubbles). The bipolar outflow grew continuously inside the expanding bubbles. We theoretically derived the growth condition of the magnetic bubbles for our model that corresponds to a necessary condition for outflow growth. We found that the north–south asymmetrical structure of the bipolar outflow originates from the complex motions excited by accreting flows around the outer edge of the disk. The bipolar outflow comprises multiple mini-outflows and downflows (failed outflows). The mini-outflows emanate from the magnetic concentrations (magnetic patches). The magnetic patches exhibit inward drifting motions, thereby making the outflows unsteady. We demonstrate that the inward drift can be modeled using a simple magnetic patch model that considers magnetic angular momentum extraction. This study could be helpful for understanding how asymmetric and nonsteady outflows with complex substructures are produced around supermassive black holes without the help of strong radiation from accretion disks or entrainment by radio jets such as molecular outflows in radio-quiet active galactic nuclei, e.g., NGC 1377.

    DOI: 10.3847/1538-4357/ac38a8

    arXiv

    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac38a8/pdf

  • Ogawa, Shoji; Ueda, Yoshihiro; Wada, Keiichi; Mizumoto, Misaki .  Warm Absorbers in the Radiation-driven Fountain Model of Low-mass Active Galactic Nuclei .  The Astrophysical Journal925 ( 1 ) 55   2022.1Warm Absorbers in the Radiation-driven Fountain Model of Low-mass Active Galactic NucleiReviewed

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    DOI: 10.3847/1538-4357/ac3cb9

  • Toba, Yoshiki ; Liu, Teng search by orcid ; Urrutia, Tanya ; Salvato, Mara ; Li, Junyao ; Ueda, Yoshihiro ; Brusa, Marcella ; Yutani, Naomichi ; Wada, Keiichi ; Nishizawa, Atsushi J. ; Buchner, Johannes search by orcid ; Nagao, Tohru ; Merloni, Andrea ; Akiyama, Masayuki ; Arcodia, Riccardo ; Hsieh, Bau-Ching ; Ichikawa, Kohei ; Imanishi, Masatoshi ; Inoue, Kaiki T. ; Kawaguchi, Toshihiro ; Lamer, Georg ; Nandra, Kirpal ; Silverman, John D. ; Terashima, Yuichi .  The eROSITA Final Equatorial-Depth Survey (eFEDS): A multiwavelength view of WISE mid-infrared galaxies/active galactic nuclei .  Astronomy and Astrophysics649   2021.8The eROSITA Final Equatorial-Depth Survey (eFEDS): A multiwavelength view of WISE mid-infrared galaxies/active galactic nucleiInternational coauthorship

  • Joh, Kazuma ; Nagao, Tohru ; Wada, Keiichi ; Terao, Koki ; Yamashita, Takuji .  Do gas clouds in narrow-line regions of Seyfert galaxies come from their nuclei? .  Publications of the Astronomical Society of Japan73 ( 4 ) 1152 - 1165   2021.8Do gas clouds in narrow-line regions of Seyfert galaxies come from their nuclei?Reviewed

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  • García-Burillo, S. ; Alonso-Herrero, A. ; Ramos Almeida, C. search by orcid ; González-Martín, O. ; Combes, F. ; Usero, A. search by orcid ; Hönig, S. ; Querejeta, M. ; Hicks, E. K. S. ; Hunt, L. K. search by orcid ; Rosario, D. ; Davies, R. search by orcid ; Boorman, P. G. search by orcid ; Bunker, A. J. ; Burtscher, L. ; Colina, L. ; Díaz-Santos, T. search by orcid ; Gandhi, P. ; García-Bernete, I. ; García-Lorenzo, B. ; Ichikawa, K. ; Imanishi, M. ; Izumi, T. ; Labiano, A. ; Levenson, N. A. ; López-Rodríguez, E. ; Packham, C. search by orcid ; Pereira-Santaella, M. ; Ricci, C. ; Rigopoulou, D. ; Rouan, D. ; Shimizu, T. ; Stalevski, M. ; Wada, K. ; Williamson, D. Abstract .  The Galaxy Activity, Torus, and Outflow Survey (GATOS). I. ALMA images of dusty molecular tori in Seyfert galaxies .  Astronomy & Astrophysics652   A98   2021.8The Galaxy Activity, Torus, and Outflow Survey (GATOS). I. ALMA images of dusty molecular tori in Seyfert galaxiesInternational coauthorship

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  • Alonso-Herrero, A. ; García-Burillo, S. ; Hönig, S. F. ; García-Bernete, I. ; Ramos Almeida, C. search by orcid ; González-Martín, O. ; López-Rodríguez, E. ; Boorman, P. G. search by orcid ; Bunker, A. J. ; Burtscher, L. ; Combes, F. ; Davies, R. search by orcid ; Díaz-Santos, T. search by orcid ; Gandhi, P. ; García-Lorenzo, B. ; Hicks, E. K. S. ; Hunt, L. K. search by orcid ; Ichikawa, K. ; Imanishi, M. ; Izumi, T. ; Labiano, A. ; Levenson, N. A. ; Packham, C. search by orcid ; Pereira-Santaella, M. ; Ricci, C. ; Rigopoulou, D. ; Roche, P. search by orcid ; Rosario, D. J. ; Rouan, D. ; Shimizu, T. search by orcid ; Stalevski, M. search by orcid ; Wada, K. ; Williamson, D. .  The Galaxy Activity, Torus, and Outflow Survey (GATOS). II. Torus and polar dust emission in nearby Seyfert galaxies .  Astronomy & Astrophysics652   A99   2021.8The Galaxy Activity, Torus, and Outflow Survey (GATOS). II. Torus and polar dust emission in nearby Seyfert galaxiesReviewed International coauthorship

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    Language:English   Publishing type:Research paper (scientific journal)  

    We compare high angular resolution mid-infrared (mid-IR) and Atacama Large Millimeter/submillimeter Array (ALMA) far-infrared (far-IR) images of twelve nearby (median 21 Mpc) Seyfert galaxies selected from the Galaxy Activity, Torus, and Outflow Survey (GATOS). The mid-IR unresolved emission contributes more than 60% of the nuclear (diameters of 1.5″ ∼ 150 pc) emission in most galaxies. By contrast, the ALMA 870  μm continuum emission is mostlyresolved with a median diameter of 42 pc and typically along the equatorial direction of the torus (Paper I). The Eddington ratios and nuclear hydrogen column densities (NH) of half the sample are favorable to launching polar and/or equatorial dusty winds, according to numerical simulations. Six of these show mid-IR extended emission approximately in the polar direction as traced by the narrow line region and perpendicular to the ALMA emission. In a few galaxies, the nuclear NH might be too high to uplift large quantities of dusty material along the polar direction. Five galaxies have low NH and/or Eddington ratios and thus polar dusty winds are not likely. We generated new radiative transfer CAT3D-WIND disk+wind models and model images at 8, 12, and 700  μm. We tailored these models to the properties of the GATOS Seyferts in this work. At low wind-to-disk cloud ratios, the far-IR model images have disk-and ring-like morphologies. The characteristic "X"-shape associated with dusty winds is seen better in the far-IR at intermediate-high inclinations for the extended-wind configurations. In most of the explored models, the mid-IR emission mainly comes from the inner part of the disk and cone. Extended biconical and one-sided polar mid-IR emission is seen in extended-wind configurations and high wind-to-disk cloud ratios. When convolved to the typical angular resolution of our observations, the CAT3D-WIND model images reproduce qualitative aspects of the observed mid-and far-IR morphologies. However, low to intermediate values of the wind-to-disk ratio are required to account for the observed large fractions of unresolved mid-IR emission in our sample. This work and Paper I provide observational support for the torus+wind scenario. The wind component is more relevant at high Eddington ratios and/or active galactic nucleus luminosities, and polar dust emission is predicted at nuclear column densities of up to ∼1024 cm-2. The torus or disk component, on the other hand, prevails at low luminosities and/or Eddington ratios.

    DOI: 10.1051/0004-6361/202141219

    Scopus

  • Physically motivated X-ray obscurer models .    651   A58 - A69   2021.7Physically motivated X-ray obscurer modelsReviewed International coauthorship

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  • Taisei Uzuo , Keiichi Wada , Takuma Izumi , Shunsuke Baba , Kosei Matsumoto , Yuki Kudoh .  Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational Transitions .  The Astrophysical Journal915   89   2021.7Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational TransitionsReviewed

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.3847/1538-4357/ac013d

  • Taisei Uzuo, Keiichi Wada, Takuma Izumi, Shunsuke Baba, Kosei Matsumoto, Yuki Kudoh .  Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational Transitions .  Astrophysical Journal915 ( 2 )   2021.7Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational TransitionsReviewed

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    Authorship:Corresponding author   Publishing type:Research paper (scientific journal)  

    We studied the absorption features of CO lines against the continuum originating from the heated dust in the obscuring tori around active galactic nuclei (AGNs). We investigated the formation of absorption lines corresponding to the CO rotational transitions using three-dimensional non-LTE line transfer simulations considering the dust thermal emission. As in Papers I-III of this series, we performed post-processed radiative transfer calculations using the "radiation-driven fountain model"(Wada et al. 2016), which yields a geometrically thick obscuring structure around the nucleus. This model is consistent with the spectral energy distribution of the nearest type-2 Seyfert galaxy, the Circinus galaxy. We found that the continuum-subtracted channel maps of J = 4-3 and higher transitions show absorption regions along the disk midplane for an edge-on viewing angle. The spectra consist of multiple absorption and emission features, reflecting the internal inhomogeneous and turbulent structure of the torus. The deepest absorption feature is caused by the gas on the near side of the torus between r = 10 and 15 pc, which is located in front of the AGN-heated dust inside r ≃ 5 pc. We also found that a spatial resolution of 0.5-1.0 pc is necessary to resolve the absorption features. Moreover, the inclination angle must be close to the edge-on angle (i.e., ⪆85 ) to observe the absorption features. The findings of the present study imply that combining our radiation-hydrodynamic model with high-resolution observations of CO (7-6) by ALMA can provide new information about the internal structure of the molecular tori in nearby AGNs.

    DOI: 10.3847/1538-4357/ac013d

    Scopus

  • Johannes Buchner, Murray Brightman, Mislav Baloković, Keiichi Wada, Franz E. Bauer, Kirpal Nandra .  Physically motivated X-ray obscurer models .  Astronomy and Astrophysics651   2021.7Physically motivated X-ray obscurer modelsReviewed

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    The nuclear obscurer of active galactic nuclei (AGN) is poorly understood in terms of its origin, geometry, and dynamics. Aims. We investigate whether physically motivated geometries emerging from hydro-radiative simulations can be dierentiated with X-ray reflection spectroscopy. Methods. For two new geometries, the radiative fountain model and a warped disk, we release spectral models produced with the ray tracing code XARS. We contrast these models with spectra of three nearby AGN taken by NuSTAR and Swift/BAT. Results. Along heavily obscured sightlines, the models present dierent 420 keV continuum spectra. These can be dierentiated by current observations. Spectral fits of the Circinus Galaxy favour the warped disk model over the radiative fountain, and clumpy or smooth torus models. Conclusions. The necessary reflector (NH 1025 cm2) suggests a hidden population of heavily Compton-thick AGN amongst local galaxies. X-ray reflection spectroscopy is a promising pathway to understand the nuclear obscurer in AGN.

    DOI: 10.1051/0004-6361/201834963

    Scopus

  • Keiichi Wada, Yusuke Tsukamoto, Eiichiro Kokubo .  Formation of "Blanets"from Dust Grains around the Supermassive Black Holes in Galaxies .  Astrophysical Journal909 ( 1 ) 96 - 105   2021.3Reviewed

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)  

    In Wada et al. (2019), we proposed for the first time that a new class of planets, blanets, can be formed around supermassive black holes in the galactic center. Here, we investigate the dust coagulation processes and physical conditions of the blanet formation outside the snowline (r snow ∼ several parsecs) in more detail, especially considering the effect of the radial drift of the dust aggregates. We found that a dimensionless parameter, where v t is the turbulent velocity and c s is the sound velocity, describing the turbulent viscosity should be smaller than 0.04 in the circumnuclear disk to prevent the destruction of the aggregates due to collision. The formation timescale of blanets τ GI at r snow is, τ GI ≃ 70-80 Myr for α = 0.01 - 0.04 and M BH = 106 M o˙. The mass of the blanets ranges from ∼20M E to 3000M E in r < 4 pc for α = 0.02 (M E is the Earth mass), which is in contrast with 4M E-6M E for the case without the radial drift. Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei (L bol ∼ 1042 erg s-1) during their lifetime (≲108 yr).

    DOI: 10.3847/1538-4357/abd40a

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/2007.15198v2

  • Keiichi Wada, Yuki Kudoh, Naomichi Yutani, Nozomu Kawakatu, Thaisa Storchi Bergmann, William Forman, Roderik Overzier, Rogério Riffel .  Nature of inflows and outflows in AGNs .  Proceedings of the International Astronomical Union359   297 - 306   2021

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    Language:English   Publishing type:Research paper (international conference proceedings)  

    Despite many theoretical studies and observations, we still do not fully understand the feeding mechanism in AGNs even in nearby galaxies, and how feedback from AGNs affects the gas dynamics itself in the galactic central regions. In this article, we summarize our recent theoretical studies and preliminary results in terms of the mass inflow and outflows on sub-parsec to 100 parsecs scales around AGNs. We introduce different studies: 1) How do galaxy-galaxy mergers trigger AGN activity and obscuration?, 2) How do the radiative feedback affect formation of outflows and obscuration of the nucleus? and 3) How does the AGN plus starburst feedback contribute to the obscuration?

    DOI: 10.1017/S1743921320004251

    Scopus

  • Kudo Yuki, Wada Keiichi, Norman Colin .  Multiphase Circumnuclear Gas in a Low-Beta Disk: Turbulence and Magnetic Field Reversals .  The Astrophysical Journal904   9 - 23   2020.11Multiphase Circumnuclear Gas in a Low-Beta Disk: Turbulence and Magnetic Field ReversalsReviewed

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    DOI: 10.3847/1538-4357/abba39

  • Masatoshi Imanishi,Dieu D. Nguyen,Keiichi Wada,Yoshiaki Hagiwara, Satoru Iguchi,Takuma Izumi,Nozomu Kawakatu, Kouichiro Nakanishi, Kyoko Onishi .  ALMA 0.''02-RESOLUTION OBSERVATIONS REVEAL HCN-ABUNDANCE-ENHANCED COUNTER-ROTATING AND OUTFLOWING DENSE MOLECULAR GAS AT THE NGC 1068 NUCLEUS .  The Astrophysical Journal902   99 - 123   2020.10ALMA 0.''02-RESOLUTION OBSERVATIONS REVEAL HCN-ABUNDANCE-ENHANCED COUNTER-ROTATING AND OUTFLOWING DENSE MOLECULAR GAS AT THE NGC 1068 NUCLEUSReviewed

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  • S. Aalto, N. Falstad, S. Muller, K. Wada 他 .  ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377 .  Astronomy and Astrophysics640   104 - 119   2020.8ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377Reviewed

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  • S. Aalto, N. Falstad, S. Muller, K. Wada, J. S. Gallagher, S. König, K. Sakamoto, W. Vlemmings, C. Ceccobello, K. Dasyra, F. Combes, S. García-Burillo, Y. Oya, S. Martín, P. Van Der Werf, A. S. Evans, J. Kotilainen .  ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377 .  Astronomy and Astrophysics640   2020.8

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    Submillimetre and millimetre line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs) and their mechanical feedback. With very high-resolution (0.′′ ″02 × 0.′′ ″03 (2 × 3 pc)) ALMA 345 GHz observations of CO 3-2, HCO+ 4-3, vibrationally excited HCN 4-3 ν2 = 1f, and continuum we have studied the remarkable, extremely radio-quiet, molecular jet and wind of the lenticular galaxy NGC 1377. The outflow structure is resolved, revealing a 150 pc long, clumpy, high-velocity (∼600 km s-1), collimated molecular jet where the molecular emission is emerging from the spine of the jet with an average diameter of 3-7 pc. The jet widens to 10-15 pc about 25 pc from the centre, which is possibly due to jet-wind interactions. A narrow-angle (50°-70°), misaligned and rotating molecular wind surrounds the jet, and both are enveloped by a larger-scale CO-emitting structure at near-systemic velocity. The jet and narrow wind have steep radial gas excitation gradients and appear turbulent with high gas dispersion (σ > 40 km s-1). The jet shows velocity reversals that we propose are caused by precession, or more episodic directional changes. We discuss the mechanisms powering the outflow, and we find that an important process for the molecular jet and narrow wind is likely magneto-centrifugal driving. In contrast, the large-scale CO-envelope may be a slow wind, or cocoon that stems from jet-wind interactions. An asymmetric, nuclear r ∼ 2 pc dust structure with a high inferred molecular column density N(H2) ∼ 1.8 × 1024 cm-2 is detected in continuum and also shows compact emission from vibrationally excited HCN. The nuclear dust emission is hot (Td > 180 K) and its luminosity is likely powered by a buried AGN. The lopsided structure appears to be a warped disk, which is responsible for a significant part of the nuclear obscuration and possibly formed as a result of uneven gas inflows. The dynamical mass inside r = 1.4 pc is estimated to 9-3+2 × 106 M, implying that the supermassive black hole (SMBH) has a high mass with respect to the stellar velocity dispersion of NGC 1377. We suggest that the SMBH of NGC 1377 is currently in a state of moderate growth, at the end of a more intense phase of accretion and also evolving from a state of more extreme nuclear obscuration. The nuclear growth may be fuelled by low-angular momentum gas inflowing from the gas ejected in the molecular jet and wind. Such a feedback-loop of cyclic outflows and central accretion could explain why there is still a significant reservoir of molecular gas in this ageing, lenticular galaxy. A feedback-loop would be an effective process in growing the nuclear SMBH and thus would constitute an important phase in the evolution of NGC 1377. This also invites new questions as to SMBH growth processes in obscured, dusty galaxies.

    DOI: 10.1051/0004-6361/202038282

    Scopus

  • Kawakatu Nozomu, Wada Keiichi, Ichikawa Kohei .  Obscuring Fraction of Active Galactic Nuclei Implied by Supernova and Radiative Feedbacks .  The Astrophysical Journal889 ( 2 ) 84 - 93   2020.2Obscuring Fraction of Active Galactic Nuclei Implied by Supernova and Radiative FeedbacksReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

  • Kawaguchi Takeru, Yutani Naomichi, Wada, Keiichi .  Mass accretion toward black holes in final phase of galaxy mergers .  The Astrophysical Journal890 ( 2 ) 125 - 136   2020.2Mass accretion toward black holes in final phase of galaxy mergersReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

  • Keiichi Wada, Yusuke Tsukamoto, Eiichiro Kokubo .  Formation of Planets around Supermassive Black Holes in Active Galactic Nuclei .  The Astrophysical Journal   2019.12Formation of Planets around Supermassive Black Holes in Active Galactic Nuclei

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

  • Kudoh Yuki, Wada Keiichi .  Magneto Rotational Instability in Magnetized AGN Tori .  Galaxies6 ( 4 ) 139   2018.12Magneto Rotational Instability in Magnetized AGN ToriReviewed

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    Language:English   Publishing type:Research paper (scientific journal)  

    It is widely believed that in active galactic nuclei (AGNs) a supermassive black hole with an accretion disk is surrounded by an optically and geometrically thick torus at sub-parsec scale. However, it is not clear how is the mass supply toward the central engine caused and how it is related with the internal structures of the tori. The magnetic field in the tori may contribute to the accretion process via the magneto-rotational instability (MRI). Using global three dimensional magnetohydrodynamic (MHD) simulations taking the effects of X-ray heating and radiative cooling into account studied the numerical resolution for azimuthal direction for MRI driving. We found that a strongly magnetized disk consisted of a cold ($< 10^3$ K) and warm ($10^4$ K) gas is developed in about 30 rotational periods. We also found in high resolution model that the mean azimuthal magnetic fields reverse their direction quasi-periodically. We confirmed that the typical wave length of the MRI should be resolved with a least 20 azimuthal grid cells.

    DOI: 10.3390/galaxies6040139

  • Wada Keiichi, Yonekura Kensuke, Nagao Tohru .  Circumnuclear Multiphase Gas in Circinus Galaxy. III. Structure of the Nuclear Ionized Gas .  The Astrophysical Journal867   49 - 56   2018.11Circumnuclear Multiphase Gas in Circinus Galaxy. III. Structure of the Nuclear Ionized GasReviewed

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    We investigate the properties of the ionized gas irradiated by an active galactic nucleus (AGN) based on our “radiation-driven fountain” model for the nearest type-2 Seyfert galaxy, the Circinus galaxy. We conducted “quasi-three-dimensional” spectral analysis using the spectral synthesis code CLOUDY and obtained the surface brightness distributions of lines, such as Hα, Hβ, [O III], [N II], and [S II] for the central 16 pc region. The ionized regions observed based on these lines show a conical morphology around the rotation axis, even if we do not phenomenologically postulate the presence of an optically thick “torus.” This region also shows non-uniform internal structures, reflecting the inhomogeneous structure of fountain flows. Using ionization diagnostic diagrams, we investigated the spectral properties of the ionized gas. The diagrams based on the line ratios of [N II]/Hα and [S II]/Hα show that most regions of the cone have the same properties as those in the narrow line regions (NLRs) in AGNs, whereas using [O I]/Hα, the central 10 pc regions are rather LINER-like. The gas density, temperature, and ionizing parameter in regions identified as “NLR” are typically n ∼ 300–1500 cm‑3, T ∼ (1–3) × 104 K, and U ∼ 0.01, respectively. The morphology and [O III] intensity are similar to the base of the observed [O III] cone in the Circinus galaxy, implying some physical connections with the origin of the ∼100 pc scale NLR.

    DOI: 10.3847/1538-4357/aae204

  • Izumi, Takuma; Wada, Keiichi; Fukushige, Ryosuke; Hamamura, Sota; Kohno, Kotaro .  Circumnuclear Multiphase Gas in the Circinus Galaxy. II. The Molecular and Atomic Obscuring Structures Revealed with ALMA .  The Astrophysical Journal867   48 - 68   2018.11Circumnuclear Multiphase Gas in the Circinus Galaxy. II. The Molecular and Atomic Obscuring Structures Revealed with ALMAReviewed

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    We used the Atacama Large Millimeter/Submillimeter Array (ALMA) to map the CO(3–2) and [C I](1–0) lines, as well as their underlying continuum emission, from the central ∼200 pc region of the Circinus galaxy that hosts the nearest type 2 Seyfert-class active galactic nucleus (AGN), with a spatial resolution of ∼6–15 pc. The lines and continuum-emitting regions consist of a circumnuclear disk (CND; 74 pc × 34 pc) and spiral arms. The distribution of the continuum emission revealed a temperature-dependent dust geometry and possibly polar dust elongation in the torus region. The molecular mass of the CND is {M}{{H}2}∼ 3× {10}6 {M}ȯ , with a beam-averaged H2 column density of ∼5 × 1023 cm‑2 toward the AGN position, which contributes significantly to the nuclear obscuration. The [C I](1–0)/CO(3–2) ratio at the AGN position is unusually high, suggesting an X-ray-dominated region-type chemistry. We decomposed the observed velocity fields into rotational and dispersion components, and revealed a multiphase dynamic nature in the r ≲ 10 pc torus region, i.e., the diffuse atomic gas is more spatially extended along the vertical direction of the disk than the dense molecular gas. Through comparisons with our model predictions based on the radiation-driven fountain scheme, we indicate that atomic outflows are the driver of the geometrical thickness of the atomic disk. This supports the validity of the radiation-driven fountain scheme in the vicinity of this AGN, which would explain the longstanding mystery of the physical origin of the AGN torus.

    DOI: 10.3847/1538-4357/aae20b

  • Imanishi, Masatoshi; Nakanishi, Kouichiro; Izumi, Takuma; Wada, Keiichi .  ALMA Reveals an Inhomogeneous Compact Rotating Dense Molecular Torus at the NGC 1068 Nucleus Authors .  The Astrophysical Journal Letters   2018.2ALMA Reveals an Inhomogeneous Compact Rotating Dense Molecular Torus at the NGC 1068 Nucleus AuthorsReviewed

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    DOI: 10.3847/2041-8213/aaa8df

  • Wada Keiichi, Fukushige Ryosuke, Izumi Takuma, Tomisaka, Kohji .  Circumnuclear Multi-phase Gas in the Circinus Galaxy. I. Non-LTE Calculations of CO Lines10.3847/1538-4357/aa9e53 .  The Astrophysical Journal852 ( 2 ) 88 - 99   2018.1Circumnuclear Multi-phase Gas in the Circinus Galaxy. I. Non-LTE Calculations of CO Lines10.3847/1538-4357/aa9e53Reviewed

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    In this study, we investigate the line emissions from cold molecular gas based on our previous “radiation-driven fountain model,” which reliably explains the spectral energy distribution of the nearest type 2 Seyfert galaxy, the Circinus galaxy. Using a snapshot of the best-fit radiation-hydrodynamic model for the central r≤slant 16 pc, in which non-equilibrium X-ray-dominated region chemistry is solved, we conduct post-processed non-local thermodynamic equilibrium radiation transfer simulations for the CO lines. We obtain a spectral line energy distribution with a peak around J≃ 6, and its distribution suggests that the lines are not thermalized. However, for a given line of sight, the optical depth distribution is highly non-uniform between {τ }ν \ll 1 and {τ }ν \gg 1. The CO-to-H2 conversion factor ({X}{CO}), which can be directly obtained from the results and is not a constant, depends strongly on the integrated intensity and differs from the fiducial value for local objects. {X}{CO} exhibits a large dispersion of more than one order of magnitude, reflecting the non-uniform internal structure of a “torus.” In addition, we found that the physical conditions differ between grid cells on a scale of a few parsecs along the observed lines of sight; therefore, a specific observed line ratio does not necessarily represent a single physical state of the interstellar medium.

    DOI: 10.3847/1538-4357/aa9e53

  • M. Schartmann, J. Mould, K. Wada, A. Burkert, M. Durré, M. Behrendt, R. I. Davies, L. Burtscher .  The life cycle of starbursting circumnuclear gas discs .  Monthly Notices of the Royal Astronomical Society473 ( 1 ) 953 - 968   2018.1Invited Reviewed

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    High-resolution observations from the submm to the optical wavelength regime resolve the central few 100 pc region of nearby galaxies in great detail. They reveal a large diversity of features: thick gas and stellar discs, nuclear starbursts, inflows and outflows, central activity, jet interaction, etc. Concentrating on the role circumnuclear discs play in the life cycles of galactic nuclei, we employ 3D adaptive mesh refinement hydrodynamical simulations with the RAMSES code to self-consistently trace the evolution from a quasi-stable gas disc, undergoing gravitational (Toomre) instability, the formation of clumps and stars and the disc's subsequent, partial dispersal via stellar feedback. Our approach builds upon the observational finding that many nearby Seyfert galaxies have undergone intense nuclear starbursts in their recent past and in many nearby sources star formation is concentrated in a handful of clumps on a few 100 pc distant from the galactic centre. We show that such observations can be understood as the result of gravitational instabilities in dense circumnuclear discs. By comparing these simulations to available integral field unit observations of a sample of nearby galactic nuclei, we find consistent gas and stellar masses, kinematics, star formation and outflow properties. Important ingredients in the simulations are the self-consistent treatment of star formation and the dynamical evolution of the stellar distribution as well as the modelling of a delay time distribution for the supernova feedback. The knowledge of the resulting simulated density structure and kinematics on pc scale is vital for understanding inflow and feedback processes towards galactic scales.

    DOI: 10.1093/mnras/stx2381

    Scopus

  • S. Aalto, S. Muller, F. Costagliola, K. Sakamoto, J. S. Gallagher, N. Falstad, S. König, K. Dasyra, K. Wada, F. Combes, S. García-Burillo, L. E. Kristensen, S. Martín, P. Van Der Werf, A. S. Evans, J. Kotilainen .  Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377 .  Astronomy and Astrophysics608   2017.12

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    High-resolution submillimeter line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs). With high-resolution (0.? 06 × 0.? 05 (6 × 5 pc)) ALMA 690 GHz observations we have found bright (T > 80 K) and compact (full width half maximum size (FWHM) size of 10 × 7 pc) CO 6-5 line emission in the nuclear region of the extremely radio-quiet galaxy NGC 1377. The CO 6-5 intensity is partially aligned with the previously discovered jet/outflow of NGC 1377 and is tracing dense (n > 10 cm ) hot molecular gas at the base of the outflow. The velocity structure is complex and shifts across the jet/outflow are discussed in terms of separate overlapping kinematical components or rotation. High-velocity gas (Δv ± 145km s ) is detected inside r < 2-3 pc and we suggest that it is emerging from an inclined rotating disk or torus of position angle PA = 140° ± 20° with a dynamical mass of 3 × 10 M . This mass is consistent with that of a supermassive black hole (SMBH), as inferred from the M-σ relation. The gas mass of the proposed disk/torus constitutes <3% of the dynamical mass inside a radius of 3 pc. In contrast to the intense CO 6-5 line emission, we do not detect 690 GHz dust continuum in the nuclear region of NGC 1377. The upper limit of S(690 GHz) ≲ 2 mJy implies an H column density N(H ) < 3 × 10 cm (averaged in the central 6 × 5 pc beam). This is inconsistent with a Compton thick (CT) source and we discuss the possibility that CT obscuration may instead be occurring on smaller subparsec scales or in a larger foreground structure. From SED fitting we suggest that half of the IR emission of NGC 1377 is nuclear and the rest, mostly the far-infrared (FIR), is emerging from larger scales. The extreme radio quietness, and the lack of emission from other star formation tracers, raise questions on the origin of the FIR emission. We discuss the possibility that it arises from AGN-heated dust along the minor axis. B ⊙ 2 2 4 -3 -1 6 23 -2

    DOI: 10.1051/0004-6361/201730650

    Scopus

  • Aalto S., Wada, K. 他13名 .  Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377 .  Astronomy & Astrophysics   2017.12Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377Invited Reviewed

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  • Inoue Susumu, Uchiyama Yasunobu, Arakawa Masanori, Renaud Matthieu, Wada Keiichi .  Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk .  The Astrophysical Journal849 ( 1 ) 22 - 39   2017.11Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic DiskReviewed

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    DOI: 10.3847/1538-4357/aa8dfa

  • Izumi, T. 他 .  On the disappearance of a cold molecular torus around the low-luminosity active galactic nucleus of NGC 1097 .  The Astrophysical Journal Letters845   5 - 13   2017.8On the disappearance of a cold molecular torus around the low-luminosity active galactic nucleus of NGC 1097Reviewed

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  • T. Izumi, K. Kohno, K. Fathi, E. Hatziminaoglou, R. I. Davies, S. Martin, S. Matsushita, E. Schinnerer, D. Espada, S. Aalto, K. Onishi, J. L. Turner, M. Imanishi, K. Nakanishi, D. S. Meier, K. Wada, N. Kawakatu, T. Nakajima .  On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097 .  Astrophysical Journal Letters845 ( 1 )   2017.8

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    We used the Atacama Large Millimeter/Submillimeter Array to map the CO(3-2) and the underlying continuum emissions around the type-1 low-luminosity active galactic nucleus (LLAGN; bolometric luminosity erg s ) of NGC 1097 at ∼10 pc resolution. These observations revealed a detailed cold gas distribution within a ∼100 pc of this LLAGN. In contrast to the luminous Seyfert galaxy NGC 1068, where a ∼7 pc cold molecular torus was recently revealed, a distinctively dense and compact torus is missing in our CO(3-2) integrated intensity map of NGC 1097. Based on the CO(3-2) flux, the gas mass of the torus of NGC 1097 would be a factor of 2-3 less than that found for NGC 1068 by using the same CO-to-H conversion factor, which implies less active nuclear star formation and/or inflows in NGC 1097. Our dynamical modeling of the CO(3-2) velocity field implies that the cold molecular gas is concentrated in a thin layer as compared to the hot gas traced by the 2.12 μm H emission in and around the torus. Furthermore, we suggest that NGC 1097 hosts a geometrically thinner torus than NGC 1068. Although the physical origin of the torus thickness remains unclear, our observations support a theoretical prediction that geometrically thick tori with high opacity will become deficient as AGNs evolve from luminous Seyferts to LLAGNs. -1 2 2

    DOI: 10.3847/2041-8213/aa808f

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  • Wada Keiichi, Schartmann Marc, Meijerink Rowin .  Multi-phase Nature of a Radiation-Driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus .  The Astrophysical Journal Letters828 ( 2 ) L19 - L25   2016.9Multi-phase Nature of a Radiation-Driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus

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    DOI: 10.3847/2041-8205/828/2/L19

  • Authors: Nomura Mariko, Ohsuga Ken, Takahashi Hiroyuki R., Wada Keiichi, Yoshida Tessei .  Radiation Hydrodynamic Simulations of Line-Driven Disk Winds for Ultra Fast Outflows .  Publications of Astronomical Society of Japan   2016.1Radiation Hydrodynamic Simulations of Line-Driven Disk Winds for Ultra Fast OutflowsReviewed

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Astronomical Society of Japan  

    DOI: 10.1093/pasj/psv124

  • Keiichi Wada .  Obscuring Fraction of Active Galactic Nuclei: Implications from Radiation-driven Fountain Models .  The Astrophysical Journal812   82 - 95   2015.10Obscuring Fraction of Active Galactic Nuclei: Implications from Radiation-driven Fountain ModelsReviewed

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  • M. Schartmann, K. Wada, M. A. Prieto, A. Burkert, and K. R. W. Tristram .  Time-resolved infrared emission from radiation-driven central obscuring structures in Active Galactic Nuclei .  Monthly Notices of Royal Astronomical Society445 ( 4 ) 3878 - 3891   2014.12Time-resolved infrared emission from radiation-driven central obscuring structures in Active Galactic NucleiReviewed

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  • Mariko NOMURA, Ken OHSUGA, Keiichi WADA, Hajime SUSA, and Toru MISAWA .  Modeling Line-Driven Disk Wind for Broad Absorption Lines of Quasars .  Publications of Astronomical Society of Japan65   40 - 49   2013.4Modeling Line-Driven Disk Wind for Broad Absorption Lines of QuasarsReviewed

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  • Baba, Junichi; Saitoh, Takayuki R.; Wada, Keiichi .  Dynamics of Non-steady Spiral Arms in Disk Galaxies .  The Astrophysical Journal763 ( 1 ) 46 - 59   2013.1Dynamics of Non-steady Spiral Arms in Disk GalaxiesReviewed

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  • Keiichi Wada .  Radiation-driven Fountain and Origin of Torus around Active Galactic Nuclei .  Astrophysical Journal758 ( 1 ) 66   2012.10Radiation-driven Fountain and Origin of Torus around Active Galactic NucleiReviewed

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  • Makoto Miyoshi, Yoshiharu Asaki, Keiichi Wada, Hiroshi Imai .  Analysis of H2O Masers in Sharpless 269 using VERA Archival Data --- Distribution of the Masers and Their Time Variations .  New Astronomy17 ( 6 ) 553 - 564   2012.8Analysis of H2O Masers in Sharpless 269 using VERA Archival Data --- Distribution of the Masers and Their Time VariationsReviewed

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  • Hidenori Matsui, Takayuki R. Saitoh, Junichiro Makino, Keiichi Wada, Kohji Tomisaka, Eiichiro Kokubo, Hiroshi Daisaka, Takashi Okamoto, Naoki Yoshida .  ORIGIN OF MULTIPLE NUCLEI IN ULTRALUMINOUS INFRARED GALAXIES .  Astrophysical Journal746 ( 1 ) 26   2012.2ORIGIN OF MULTIPLE NUCLEI IN ULTRALUMINOUS INFRARED GALAXIESReviewed

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  • Sungsoo Kim, Takayuki Saitoh, Myoungwon Jeon, Donald F. Figer, David Merritt, and Keiichi Wada .  Nuclear Star-Forming Ring of the Milky Way: Simulations .  The Astrophysical Journal Letters735   L11 - L15   2011.7Nuclear Star-Forming Ring of the Milky Way: Simulations Reviewed

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  • K.Wada, J. Baba, T.R. Saitoh, .  Interplay between Stellar Spirals and the ISM in Galactic Disks .  The Astrophysical Journal735   1 - 9   2011.7Interplay between Stellar Spirals and the ISM in Galactic DisksReviewed

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  • Fujii, M., Baba, J., Saitoh, T.R., Makino, J., Kokubo, E., Wada, K. .  The Dynamics of Pure Stellar Galactic Disks with Spiral Arms, .  The Astrophysical Journal730   109 - 122   2011.1The Dynamics of Pure Stellar Galactic Disks with Spiral Arms,Reviewed

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  • BABA, Junichi, SAITOH, Takayuki R., WADA, Keiichi .  On the Interpretation of the l-v Features in the Milky Way Galaxy .  Publ. Astron. Soc. Japan 62   1413 - 1422   2010.12On the Interpretation of the l-v Features in the Milky Way GalaxyReviewed

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  • Junichi Baba, Takayuki R. Saitoh, Keiichi Wada .  On the Interpretation of the l-v Features in the Milky Way Galaxy .  Publications of the Astronomical Society of Japan, Astronomical Society of Japan   2010.12On the Interpretation of the l-v Features in the Milky Way GalaxyReviewed

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  • Nozomu Kawakatu, Keiichi Wada .  Formation of High-redshift (z>6) Quasars Driven by Nuclear Starbursts .  The Astrophysical Journal, American Astronomical Society706 ( 1 ) 676 - 686   2009.11Formation of High-redshift (z>6) Quasars Driven by Nuclear StarburstsReviewed

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  • Keiichi Wada .  Gaseous structure excited by resonances in a non-axisymmetric gravitational potential .      1993.12Gaseous structure excited by resonances in a non-axisymmetric gravitational potential

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    Language:English   Publishing type:Doctoral thesis  

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Books

  • 宇宙流体力学の基礎

    福江 純和田 桂一梅村 雅之( Role: Joint author)

    日本評論社  2014.2 

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    Language:Japanese Book type:Scholarly book

  • 巨大ブラックホールと宇宙

    谷口義明、和田桂一( Role: Joint author)

    丸善出版  2012.1 

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    Language:Japanese Book type:Scholarly book

  • ピーターソン 活動銀河核

    和田桂一, 粟木久光, 亀野誠二, 谷口義明, 寺島雄一, 長尾透( Role: Edit)

    丸善株式会社  2010.5 

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    Language:Japanese Book type:Scholarly book

MISC

  • The Galaxy Activity, Torus, and Outflow Survey (GATOS): I. ALMA images of dusty molecular tori in Seyfert galaxies Reviewed

    S. García-Burillo, A. Alonso-Herrero, C. Ramos Almeida, O. González-Martín, F. Combes, A. Usero, S. Hönig, M. Querejeta, E. K.S. Hicks, L. K. Hunt, D. Rosario, R. Davies, P. G. Boorman, A. J. Bunker, L. Burtscher, L. Colina, T. Díaz-Santos, P. Gandhi, I. García-Bernete, B. García-Lorenzo, K. Ichikawa, M. Imanishi, T. Izumi, A. Labiano, N. A. Levenson, E. López-Rodríguez, C. Packham, M. Pereira-Santaella, C. Ricci, D. Rigopoulou, D. Rouan, T. Shimizu, M. Stalevski, K. Wada, D. Williamson

    Astronomy and Astrophysics   652   A98 - A98   2021.8

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    Publisher:EDP Sciences  

    We present the first results of the Galaxy Activity, Torus, and Outflow Survey (GATOS), a project aimed at understanding the properties of the dusty molecular tori and their connection to the host galaxy in nearby Seyfert galaxies. Our project expands the range of active galactic nuclei (AGN) luminosities and Eddington ratios covered by previous surveys of Seyferts conducted by the Atacama Large Millimeter Array (ALMA), allowing us to study the gas feeding and feedback cycle in a combined sample of 19 Seyferts. We used ALMA to obtain new images of the emission of molecular gas and dust using the CO(3-2) and HCO+(4-3) lines as well as their underlying continuum emission at 870 μm with high spatial resolutions (0.1″ ∼ 7-13 pc) in the circumnuclear disks (CND) of ten nearby (D < 28 Mpc) Seyfert galaxies selected from an ultra-hard X-ray survey. Our new ALMA observations detect 870 μm continuum and CO line emission from spatially resolved disks located around the AGN in all the sources. The bulk of the 870 μm continuum flux can be accounted for by thermal emission from dust in the majority of the targets. For most of the sources, the disks show a preponderant orientation perpendicular to the AGN wind axes, as expected for dusty molecular tori. The median diameters and molecular gas masses of the tori are ∼42 pc and ∼6 × 105 M· , respectively. We also detected the emission of the 4-3 line of HCO+ in four GATOS targets. The order of magnitude differences found in the CO/HCO+ ratios within our combined sample point to a very different density radial stratification inside the dusty molecular tori of these Seyferts. We find a positive correlation between the line-of-sight gas column densities responsible for the absorption of X-rays and the molecular gas column densities derived from CO toward the AGN in our sources. Furthermore, the median values of both column densities are similar. This suggests that the neutral gas line-of-sight column densities of the dusty molecular tori imaged by ALMA significantly contribute to the obscuration of X-rays. The radial distributions of molecular gas in the CND of our combined sample show signs of nuclear-scale molecular gas deficits. We also detect molecular outflows in the sources that show the most extreme nuclear-scale gas deficits in our sample. These observations find for the first time supporting evidence that the imprint of AGN feedback is more extreme in higher luminosity and/or higher Eddington ratio Seyfert galaxies.

    DOI: 10.1051/0004-6361/202141075

    Scopus

  • Erratum: Planet formation around super massive black holes in the active galactic nuclei (Astrophysical Journal (2019) 886 (107))

    Wada K.

    Astrophysical Journal   907 ( 1 )   2021.1

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    Authorship:Lead author   Publisher:Astrophysical Journal  

    DOI: 10.3847/1538-4357/abd7ea

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  • ALMA 0 02 resolution observations reveal HCN-abundance-enhanced counter-rotating and outflowing dense molecular gas at the NGC 1068 nucleus

    Masatoshi Imanishi, Dieu D. Nguyen, Keiichi Wada, Yoshiaki Hagiwara, Satoru Iguchi, Takuma Izumi, Nozomu Kawakatu, Kouichiro Nakanishi, Kyoko Onishi

    Astrophysical Journal   902 ( 2 )   2020.10

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    We present ALMA ∼0 02 resolution observations of the nucleus of the nearby (∼14 Mpc) type 2 active galactic nucleus NGC 1068 at HCN/HCO /HNC J = 3-2 lines, as well as at their C isotopologue and vibrationally excited lines, to scrutinize the morphological, dynamical, chemical, and physical properties of dense molecular gas in the putative dusty molecular torus around a mass-accreting supermassive black hole. We confirm almost east-west-oriented dense molecular gas emission both morphologically and dynamically, which we regard as coming from the torus. Bright emission is compact (≲3 pc), and low-surface-brightness e≲mission extends out to 5-7 pc. These dense molecular gas properties are not symmetric between the eastern and western torus. The HCN J = 3-2 emission is stronger than the HCO J = 3-2 emission within the ∼7 pc torus region, with an estimated dense molecular mass of (0.4-1.0) × 10 M . We interpret that HCN abundance is enhanced in the torus. We detect signatures of outflowing dense molecular gas and a vibrationally excited HCN J = 3-2 line. Finally, we find that in the innermost (≲1 pc) part of the torus, the dense molecular line rotation velocity, relative to the systemic velocity, is the opposite of that in the outer (≳ pc) part, in both the eastern and western torus. We prefer a scenario of counter-rotating dense molecular gas with innermost almost Keplerian rotation and outer slowly rotating (far below Keplerian) components. Our high-spatial-resolution dense molecular line data reveal that torus properties of NGC 1068 are much more complicated than the simple axisymmetrically rotating torus picture in the classical active galactic nucleus unification paradigm. + 13 + 6 e

    DOI: 10.3847/1538-4357/abaf50

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/2008.08101v1

  • Mass Accretion toward Black Holes in the Final Phase of Galaxy Mergers

    Takeru Kawaguchi, Naomichi Yutani, Keiichi Wada

    Astrophysical Journal   890 ( 2 )   2020.2

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    We studied the final phases of galactic mergers, focusing on interactions between supermassive black holes (SMBHs) and the interstellar medium in a central subkiloparsec region, using an N-body/hydrodynamics code. We observed that the mass accretion rate to one SMBH (10 M ) exceeds the Eddington accretion rate when the distance between two black holes (BHs) rapidly decreases. However, this rapid accretion phase does not last for more than 10 yr, and it drops to ∼10% of the Eddington rate in the quasi-steady accretion phase. The second merger event enhances the mass accretion to the BHs; however, this phase takes place on a similar timescale to the first merger event. We also found that the active galactic nucleus (AGN) feedback and the mass accretion to BHs can coexist in the central region of merged galaxies, if the amount of feedback energy is given as (2 × 10 - 2 × 10 )Mc , where Ṁ is the accretion rate to r = 1 pc. The accretion rate is suppressed by ∼1/50 in the quasi-steady accretion phase for 0.02Ṁc . The fraction of the gas that finally falls to each BH is approximately 5%-7% of the supplied total gas mass (10 M ), and 15%-20% of the gas forms a circumnuclear gas inside 100 pc. This remnant gas heavily obscures the luminous phase of the AGNs during merger events, and the moderate AGN feedback does not alter this property. 7 7 -4 -3 2 2 8 o- o-

    DOI: 10.3847/1538-4357/ab655a

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1912.10621v1

  • Obscuring Fraction of Active Galactic Nuclei Implied by Supernova and Radiative Feedbacks

    Nozomu Kawakatu, Keiichi Wada, Kohei Ichikawa

    Astrophysical Journal   889 ( 2 )   2020.2

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    We study the obscuring structure of circumnuclear disks (CNDs) by considering supernova (SN) feedbacks from nuclear starburst and the effect of anisotropic radiative pressure from active galactic nuclei (AGNs). We suppose that the mass accretion onto a central supermassive black hole (SMBH) is triggered by SN-driven turbulence within CNDs, and we explore how the structures of CNDs depend on the BH mass (M ) and AGN luminosity (L ). We find that the obscuring fraction (f ) peaks at ∼10% of the Eddington luminosity (L ), and its maximal value is f ∼ 0.6 for less massive SMBHs (e.g., M < 10 M ). This is because the scale height of CNDs is determined by the SN-driven accretion for a smaller L , while the dusty molecular gas in CNDs is blown away by the radiation pressure from AGNs beyond the critical luminosity. On the other hand, for massive SMBHs (e.g., M > 10 M ), f is always smaller than 0.2, and it is almost independent of L because the scale height of CNDs is mainly controlled by the maximal star formation efficiency (C∗ &max) in CNDs. In comparison with the obscuring fractions suggested from the mid-infrared observations of nearby AGNs, the SN plus radiative feedback model with C∗ &max; =10-7\,-1 reproduces the observations for M = 10 M well. We also find that the intense starburst or the existence of dust-free absorbers inside CNDs are necessary for explaining X-ray observations. BH AGN obs Edd obs BH o&dot; AGN BH o&dot; obs AGN BH o&dot; 8 8 8

    DOI: 10.3847/1538-4357/ab5f60

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1912.02408v1

  • Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei

    Keiichi Wada, Yusuke Tsukamoto, Eiichiro Kokubo

    Astrophysical Journal   886 ( 2 )   2019.12

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    As a natural consequence of the elementary processes of dust growth, we discovered that a new class of planets can be formed around supermassive black holes (SMBHs). We investigated a growth path from submicron sized icy dust monomers to Earth-sized bodies outside the "snow line," located several parsecs from SMBHs in low luminosity active galactic nuclei (AGNs). In contrast to protoplanetary disks, the "radial drift barrier" does not prevent the formation of planetesimals. In the early phase of the evolution, low collision velocity between dust particles promotes sticking; therefore, the internal density of the dust aggregates decreases with growth. When the porous aggregate's size reaches 0.1-1 cm, the collisional compression becomes effective, and the decrease in internal density stops. Once 10-100 m sized aggregates are formed, they are decoupled from gas turbulence, and the aggregate layer becomes gravitationally unstable, leading to the formation of planets by the fragmentation of the layer, with 10 times the mass of the Earth. The growth timescale depends on the turbulent strength of the circumnuclear disk and the black hole mass M , and it is comparable to the AGN's lifetime (∼10 yr) for low mass (M ∼ 10 M ) SMBHs. BH BH o 8 6

    DOI: 10.3847/1538-4357/ab4cf0

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1909.06748v3

  • Magneto rotational instability in magnetized AGN Tori

    Yuki Kudoh, Keiichi Wada

    Galaxies   6 ( 4 )   2018.12

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    It is widely believed that, in active galactic nuclei (AGNs), a supermassive black hole with an accretion disk is surrounded by an optically and geometrically thick torus at sub-parsec scale. However, it is not clear how the mass supply is toward the central engine caused and how it is related with the internal structures of the tori. The magnetic field in the tori may contribute to the accretion process via the magneto-rotational instability (MRI). Using global three-dimensional magnetohydrodynamic (MHD) simulations taking the effects of X-ray heating and radiative cooling into account studied the numerical resolution for azimuthal direction for MRI driving. We found that a strongly magnetized disk consisted of a cold ( < 10 K) and warm (10 K) gas is developed in about 30 rotational periods. We also found in a high resolution model that the mean azimuthal magnetic fields reverse their direction quasi-periodically. We confirmed that the typical wave length of the MRI should be resolved with a least 20 azimuthal grid cells. 3 4

    DOI: 10.3390/galaxies6040139

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1812.08419v2

  • Circumnuclear Multiphase Gas in Circinus Galaxy. III. Structure of the Nuclear Ionized Gas

    Keiichi Wada, Kensuke Yonekura, Tohru Nagao

    Astrophysical Journal   867 ( 1 )   2018.11

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    We investigate the properties of the ionized gas irradiated by an active galactic nucleus (AGN) based on our "radiation-driven fountain" model for the nearest type-2 Seyfert galaxy, the Circinus galaxy. We conducted "quasi-three-dimensional" spectral analysis using the spectral synthesis code Cloudy and obtained the surface brightness distributions of lines, such as H, Hβ, [O iii], [N ii], and [S ii] for the central 16 pc region. The ionized regions observed based on these lines show a conical morphology around the rotation axis, even if we do not phenomenologically postulate the presence of an optically thick "torus." This region also shows non-uniform internal structures, reflecting the inhomogeneous structure of fountain flows. Using ionization diagnostic diagrams, we investigated the spectral properties of the ionized gas. The diagrams based on the line ratios of [N ii]/H and [S ii]/H show that most regions of the cone have the same properties as those in the narrow line regions (NLRs) in AGNs, whereas using [O i]/H, the central 10 pc regions are rather LINER-like. The gas density, temperature, and ionizing parameter in regions identified as "NLR" are typically n ∼ 300-1500 cm , T ∼ (1-3) × 10 K, and U ∼ 0.01, respectively. The morphology and [O iii] intensity are similar to the base of the observed [O iii] cone in the Circinus galaxy, implying some physical connections with the origin of the ∼100 pc scale NLR. -3 4

    DOI: 10.3847/1538-4357/aae204

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1808.07195v1

  • Circumnuclear Multiphase Gas in the Circinus Galaxy. II. the Molecular and Atomic Obscuring Structures Revealed with ALMA

    Takuma Izumi, Keiichi Wada, Ryosuke Fukushige, Sota Hamamura, Kotaro Kohno

    Astrophysical Journal   867 ( 1 )   2018.11

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    We used the Atacama Large Millimeter/Submillimeter Array (ALMA) to map the CO(3-2) and [C i](1-0) lines, as well as their underlying continuum emission, from the central ∼200 pc region of the Circinus galaxy that hosts the nearest type 2 Seyfert-class active galactic nucleus (AGN), with a spatial resolution of ∼6-15 pc. The lines and continuum-emitting regions consist of a circumnuclear disk (CND; 74 pc × 34 pc) and spiral arms. The distribution of the continuum emission revealed a temperature-dependent dust geometry and possibly polar dust elongation in the torus region. The molecular mass of the CND is M ∼ 3 × 10 M , with a beam-averaged H column density of ∼5 × 10 cm toward the AGN position, which contributes significantly to the nuclear obscuration. The [C i](1-0)/CO(3-2) ratio at the AGN position is unusually high, suggesting an X-ray-dominated region-type chemistry. We decomposed the observed velocity fields into rotational and dispersion components, and revealed a multiphase dynamic nature in the r ≲ 10 pc torus region, i.e., the diffuse atomic gas is more spatially extended along the vertical direction of the disk than the dense molecular gas. Through comparisons with our model predictions based on the radiation-driven fountain scheme, we indicate that atomic outflows are the driver of the geometrical thickness of the atomic disk. This supports the validity of the radiation-driven fountain scheme in the vicinity of this AGN, which would explain the longstanding mystery of the physical origin of the AGN torus. H2 ⊙ 2 6 23 -2

    DOI: 10.3847/1538-4357/aae20b

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1809.09154v1

  • ALMA Reveals an Inhomogeneous Compact Rotating Dense Molecular Torus at the NGC 1068 Nucleus

    Masatoshi Imanishi, Kouichiro Nakanishi, Takuma Izumi, Keiichi Wada

    Astrophysical Journal Letters   853 ( 2 )   2018.2

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    We present the results of our ALMA Cycle 4 high-spatial-resolution (0.″04-0.″07) observations, at HCN J = 3-2 and HCO J = 3-2 lines, of the nucleus of NGC 1068, the nearby prototypical type 2 active galactic nucleus (AGN). Our previous ALMA observations identified the compact emission of these lines at the putative location of the torus around a mass-accreting supermassive black hole. We now report that we have detected the rotation of this compact emission, with the eastern and western sides being redshifted and blueshifted, respectively. Unlike the previously reported CO J = 6-5 emission, both the morphological and dynamical alignments of the HCN J = 3-2 and HCO J = 3-2 emission are roughly along the east-west direction (i.e., the expected torus direction), suggesting that these molecular lines are better probes of a rotating dense molecular gas component in the torus. The western part of the torus exhibits larger velocity dispersion and stronger emission in the HCN J = 3-2 and HCO J = 3-2 lines than the eastern part, revealing a highly inhomogeneous molecular torus. The dense molecular gas in the torus and that of the host galaxy at 0.″5-2.″0 from the AGN along the torus direction are found to be counter-rotating, suggesting an external process happened in the past at the NGC 1068 nucleus. + + +

    DOI: 10.3847/2041-8213/aaa8df

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1801.06564v1

  • Circumnuclear Multi-phase Gas in the Circinus Galaxy. I. Non-LTE Calculations of CO Lines

    Keiichi Wada, Ryosuke Fukushige, Takuma Izumi, Kohji Tomisaka

    Astrophysical Journal   852 ( 2 )   2018.1

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    In this study, we investigate the line emissions from cold molecular gas based on our previous "radiation-driven fountain model, " which reliably explains the spectral energy distribution of the nearest type 2 Seyfert galaxy, the Circinus galaxy. Using a snapshot of the best-fit radiation-hydrodynamic model for the central r ≤ 16 pc, in which non-equilibrium X-ray-dominated region chemistry is solved, we conduct post-processed non-local thermodynamic equilibrium radiation transfer simulations for the CO lines. We obtain a spectral line energy distribution with a peak around J ≃ 6, and its distribution suggests that the lines are not thermalized. However, for a given line of sight, the optical depth distribution is highly non-uniform between t ≤ 1 and t ≥ 1. The CO-to-H2 conversion factor (X ), which can be directly obtained from the results and is not a constant, depends strongly on the integrated intensity and differs from the fiducial value for local objects. XCO exhibits a large dispersion of more than one order of magnitude, reflecting the non-uniform internal structure of a "torus. " In addition, we found that the physical conditions differ between grid cells on a scale of a few parsecs along the observed lines of sight; therefore, a specific observed line ratio does not necessarily represent a single physical state of the interstellar medium. ν ν CO

    DOI: 10.3847/1538-4357/aa9e53

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1711.10117v1

  • Cosmic rays and non-thermal emission induced by accretion of cool gas onto the galactic disk

    Susumu Inoue, Yasunobu Uchiyama, Masanori Arakawa, Matthieu Renaud, Keiichi Wada

    Astrophysical Journal   849 ( 1 )   2017.11

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    On both observational and theoretical grounds, the disk of our Galaxy should be accreting cool gas with temperature ≲105 K via the halo at a rate ∼1 M yr θ. At least some of this accretion is mediated by high-velocity clouds (HVCs), observed to be traveling in the halo with velocities of a few 100 km s-1 and occasionally impacting the disk at such velocities, especially in the outer regions of the Galaxy. We address the possibility of particle acceleration in shocks triggered by such HVC accretion events, and the detectability of consequent non-thermal emission in the radio to gamma-ray bands and high-energy neutrinos. For plausible shock velocities ∼300 km s and magnetic field strengths ∼0.3-10 mG, electrons and protons may be accelerated up to ∼1-10 TeV and ∼30-10 TeV, respectively, in sufficiently strong adiabatic shocks during their lifetime of ∼10 yr. The resultant pion decay and inverse Compton gamma-rays may be the origin of some unidentified Galactic GeV-TeV sources, particularly the "dark" source HESS J1503-582 that is spatially coincident with the anomalous H I structure known as "forbidden-velocity wings." Correlation of their locations with star-forming regions may be weak, absent, or even opposite. Non-thermal radio and X-ray emission from primary and/or secondary electrons may be detectable with deeper observations. The contribution of HVC accretion to Galactic cosmic rays is subdominant, but could be non-negligible in the outer Galaxy. As the thermal emission induced by HVC accretion is likely difficult to detect, observations of such phenomena may offer a unique perspective on probing gas accretion onto the Milky Way and other galaxies. -1 -1 3 6

    DOI: 10.3847/1538-4357/aa8dfa

    Scopus

    arXiv

    Other Link: http://arxiv.org/pdf/1708.08574v2

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Presentations

  • Obscured AGNs during galaxy-galaxy mergers   Invited

    CON-quest workshop 2022  2022.1 

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    Event date: 2022.1

    Presentation type:Oral presentation (invited, special)  

  • "Unveiling the internal structures of tori by molecular absorption lines"   Invited International conference

    The Feeding and Feedback of Obscured Activity  2021.1  Chalmers University of Technology

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    Event date: 2021.1

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:オンライン   Country:Sweden  

  • Nature of inflows and outflows in AGNs   International conference

    IAU symp.359 Galaxy evolution and feedback across different environment  2020.3  International Astronomical Union

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    Event date: 2020.3

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Brazil  

  • Magneto-hydrodynamic modeling of the ISM around AGNs   International conference

    Probing AGNs and Star formation: theory and observation  2019.9  Chalmers University of Technology

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    Event date: 2019.9

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Onsala   Country:Sweden  

  • Fountain flows and obscuration by multi-phase ISM   Invited International conference

    Behind the Curtain of Dust III  2019.7  Sexten Center for Astrophysics

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    Event date: 2019.7

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Sesto   Country:Italy  

  • Dynamical pictures of tori and the multi-phase ISM   Invited

    The many faces of the AGN obscuration  2018.12 

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    Event date: 2018.12

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Puerto Varas   Country:Chile  

  • Keiichi Wada   Molecular, atomic, and ionized gas in AGN with starburst   Invited International conference

    Behind the curtain of dust II - The molecular and multi-wavelength view of activity in ULIRGs 

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    Event date: 2018.7

    Language:English   Presentation type:Oral presentation (invited, special)  

  • 和田桂一、福重亮佑、泉拓磨、富阪幸治   AGN輻射駆動噴水モデル II: 分子・原子線、X線疑似観測による検証   International conference

    日本天文学会秋季年会  日本天文学会

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    Event date: 2017.9

    Language:English   Presentation type:Oral presentation (general)  

  • 和田桂一   AGNトーラスの起源とその力学・化学進化  

    日本天文学会  日本天文学会

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    Event date: 2015.3

    Language:Japanese  

    Venue:大阪大学  

    国内学会

  • 和田桂一   Radiation-hydrodymics of the ISM with XDR chemistry around an AGN   International conference

    Astrochemistry Workshop  Astrochemistry Workshop

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    Event date: 2014.12

    Language:English  

    Venue:東京大学  

    国際学会

  • 和田桂一   Obscuration of AGNs: Implications from Radiation-driven fountain   International conference

    Evolution of SMBH with HSCs: First results from initial dataset  Evolution of SMBH with HSCs: First results from initial dataset

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    Event date: 2014.12

    Language:English  

    Venue:台北  

    国際学会

  • 和田桂一   Obscuration of AGNs: Implications from Radiation-driven fountain  

    超巨大ブラックホール研究推進連絡会第2回WS  超巨大ブラックホール研究推進連絡会第2回WS

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    Event date: 2014.11

    Language:Japanese  

    Venue:筑波大学  

    国内学会

  • 和田桂一   Radiation-driven outflows in AGNs   International conference

    Behind the curtain of dust -‐ the molecular view of activity in (U)LIRGs  Behind the curtain of dust -‐ the molecular view of activity in (U)LIRGs

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    Event date: 2014.7

    Language:English  

    Venue:Sesto、イタリア  

    国際学会

  • 和田桂一   Interaction between non-steady spirals and the ISM"   International conference

    , The Impact of Galactic Structure on Star Formation  , The Impact of Galactic Structure on Star Formation

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    Event date: 2014.2

    Language:English  

    Venue:北海道大学、札幌市(北海道)  

    国際学会

  • 和田桂一   Dynamics of the ISM in Galactic Spirals   International conference

    7th Korean Astrophysics Workshop: Dynamics of Disk Galaxies  7th Korean Astrophysics Workshop: Dynamics of Disk Galaxies

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    Event date: 2013.10

    Language:English  

    Venue:ソウル大学、韓国  

    国際学会

  • 和田桂一   Dynamical Picture of the ISM associated with Spiral Arms   International conference

    Phases of the ISM, MPIA Summer Conference  Phases of the ISM, MPIA Summer Conference

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    Event date: 2013.7

    Language:English  

    Venue:ハイデルベルグ、ドイツ  

    国際学会

  • 和田桂一   Theoretical model of feeding and feedback   International conference

    Super Massive Black Holes in the Universe: The Era of HSC Survey  Super Massive Black Holes in the Universe: The Era of HSC Survey

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    Event date: 2012.12

    Language:English  

    Venue:松山市、愛媛  

    国際学会

  • 和田桂一   Stellar and radiative feedback on the ISM around AGNs   International conference

    TIARA Workshop on Star Formation and its Environment in the Center of Galaxies  TIARA Workshop on Star Formation and its Environment in the Center of Galaxies

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    Event date: 2012.11

    Language:English  

    Venue:Hsinchu, 台湾  

    国際学会

  • Circumnuclear multi-phase gas and comparison with molecular line observations by ALMA   Invited International conference

    East-Asia AGN Workshop 2021  2021.10  Chongqing University

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    Event date: 2012.10

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Chongqing and online   Country:China  

  • Keiichi Wada   Radiative Feedback to the ISM around low-luminosity AGNs   International conference

    Jeju AGN workshop  Jeju AGN workshop

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    Event date: 2012.9

    Language:English  

    Venue:Jeju, Korea  

    国際学会

  • Keiichi Wada   Radiative Feedback to the ISM around an AGN   International conference

    IAU Symposium 292: Molecular Gas, Dust, and Star Formation in Galaxies  IAU Symposium 292: Molecular Gas, Dust, and Star Formation in Galaxies

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    Event date: 2012.8

    Language:English  

    Venue:Beijing, China  

    国際学会

  • Keiichi Wada   Star Formation around AGNs and Feedback   International conference

    Star formation in galaxies: The Herschel Era  Star formation in galaxies: The Herschel Era

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    Event date: 2011.6

    Language:English  

    Venue:リングバーグ、ドイツ  

    国際学会

  • 和田桂一   The Milky Way Project: How our home looks like?  

    Excellence Cluster Universe  Excellence Cluster Universe

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    Event date: 2011.4

    Language:Japanese  

    Venue:ガルヒン、ドイツ  

    その他

  • Keiichi Wada   Multi-phase ISM around AGN:Effect of X-ray feedback on 10s pc   International conference

    What drives the growth of black holes?  What drives the growth of black holes?

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    Event date: 2010.7

    Language:English  

    Venue:ダーラム、イギリス  

    国際学会

  • Keiichi Wada   Galactic scale star formation: Interplay between stellar spirals and the ISM   International conference

    国際天文学連合シンポジウムno. 270 “Computational Star Formation”  国際天文学連合シンポジウムno. 270 “Computational Star Formation”

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    Event date: 2010.6

    Language:English  

    Venue:スペイン、バロセロナ  

    国際学会

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Research Projects

  • 活動銀河核構造の全波長域新パラダイムの確立

    Grant number:21H04496  2021.4 - 2025.3

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    和田 桂一

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    Grant amount:\39260000 ( Direct Cost: \30200000 、 Indirect Cost:\9060000 )

  • 3次元流体モデルに基づく輻射輸送計算とALMAによる近傍およびhigh-z AGN構造の解明

    2020.4 - 2023.3

    自然科学研究機構国立天文台  ALMA科学共同研究 

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    Grant type:Competitive

  • 活動銀河核での惑星形成の可能性を探る

    2019.4 - 2022.3

    科学研究費補助金  挑戦的研究(萌芽)

  • 活動銀河核での惑星系形成の可能性を探る

    Grant number:18K18774  2018.6 - 2021.3

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    和田 桂一, 小久保 英一郎

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    Grant amount:\6240000 ( Direct Cost: \4800000 、 Indirect Cost:\1440000 )

    1995年のペガスス座51番星の発見以来、太陽系外の惑星の発見が相次ぎ、2020年現在4000個以上発見されている。いまや惑星は太陽に固有のもの ではなく、宇宙に普遍的に存在することが明らかになった。その全貌はまだ明らかではないが、太陽系は多様な惑星系の一形態に過ぎないことがわかってきたよ うに、われわれの惑星形成について常識はこの20年間で大きく変化した。枠形成形成理論には落下問題などいくつかの理論的困難が指摘されているが、現実に 惑星系が存在できるということは、その障害を回避できるということである。ここではそれらの理論的進展を踏まえ、星周囲以外での惑星形成の可能性を考える。今年度は、ミクロンサイズのダストからキロメートルサイズの微惑星へとhit-and-stick phaseや衝突圧縮phase、自己重力収縮などの成長プロセスについて詳細に考察し、巨大ブラックホール周囲の雪線の外側(数パーセク)に、地球質量の10倍程度の「惑星」(ブラネットと名付けた)が形成されることを理論的に示し、論文が米国天文学会誌(Wada, Tsukamoto, Kokubo 2019)に掲載された。また、プレスリリースを国立天文台と鹿児島大学で共同で行い、新聞他多数のネットサイトやニュートン3月号といった雑誌メディアでも紹介された。情報収集、共同研究のため、シャルマース工科大学オンサラ天文台(スウェーデン)を訪れた。 また、愛媛大学、神戸大学、マックス・プランク研究所(MPE)において、本研究内容の談話会を行った。

  • 巨大ブラックホール周りの構造の起源と進化

    2016.4 - 2020.3

    科学研究費補助金  基盤研究(B)

  • Evolution of the ISM around Supermassive Black Holes

    Grant number:16H03959  2016.4 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Wada Keiichi

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    Grant amount:\17160000 ( Direct Cost: \13200000 、 Indirect Cost:\3960000 )

    We have theoretically studied the active galactic nucleus (AGN), which consists of a supermassive black hole (SMBHs) at the centre of many galaxies. In particular, we combined the multi-dimensional radiative magnetohydrodynamic calculations and multi-wavelength pseudo-observations. We compared the numerical results with the multi-wavelength observational studies to understand1) the physical origin of the obscuring tori, 2) physics and parameters that determine the structure of the ISM around SMBH, 3) mass accretion processes and the origin of the buried AGN. We have succeeded in developing a theoretical model (radiation-driven fountain model) that explains the observational results of nearby AGNs. These studies are useful to understand the cosmological evolution of quasars and buried AGNs.

  • Coevolution and Formation of Supermassive Black Hole and circumnuclear disk by Multi-scale Theoretical Model

    Grant number:16K17670  2016.4 - 2019.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    Kawakatsu Nozomu, Wada Keiichi, Kohno Kotaro, Izumi Takuma

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    Grant amount:\3900000 ( Direct Cost: \3000000 、 Indirect Cost:\900000 )

    To understand the evolution and formation of supermassive black holes (SMBHs), it is crucial to link mass accretion processes from a galactic scale with those from an accretion disk in the vicinity of a central BH. To this aim, we have constructed a novel evolutionary model of Active galactic nuclei (AGNs) and circumnuclear disk, considering the gas fueling from host galaxies. Comparing our model with nearby observations of Seyfert galaxies, we found that CNDs likely play an important role in fuelingblack holes, whereas > kpc scale gas does not. Moreover, we predictd the obscured fraction of AGNs by taking account of the anisotropic radiation pressure from AGNs.

  • Structure formation of self-gravitational oscillator system

    Grant number:15K13536  2015.4 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    Wada Keiichi

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    Grant amount:\1430000 ( Direct Cost: \1100000 、 Indirect Cost:\330000 )

    We have made a numerical code to investigate evolution in phase and real spaces of one-dimensional oscillators interacting each other with a long-range gravitational-like force. We also developed a N-body code for 2-dimensional rotating disks consisted of many interacting particles in an external potential. Non-steady spiral-like structures are self-developed, and we analyze their group behavior in angular momentum-Jacobi integral spaces (E-J space). We found that the particles in the non-steady spirals non-linearly oscillate in the E-J space along the critical curve. This suggests that the structure formation in the real space does not result in the scattering by dynamical resonances due to the non-steady spiral arms.

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