研究者詳細 - 和田　桂一

論文 - 和田　桂一

分割表示 >> ／全件表示 60 件中 1 - 60 件目

Tanimoto, Atsushi ; Wada, Keiichi ; Odaka, Hirokazu ; Kudoh, Yuki ; Nozomu, Kawakatu . X-Ray Radiative Transfer Calculation Based on a Physics-based Model of the Sub-parsec-scale Gases around an Active Galactic Nucleus and Its Application to NGC 3783 . The Astrophysical Journal 2025年査読

Yuki Kudoh, Keiichi Wada, Nozomu Kawakatu, Mariko Nomura . Multiphase Gas Nature in the Sub-parsec Region of the Active Galactic Nuclei. III. Eddington Ratio Dependence on the Structures of Dusty and Dust-free Outflows . The Astrophysical Journal977 ( 1 ) 48 - 48 2024年12月査読国際共著国際誌

掲載種別：研究論文（学術雑誌）出版者・発行元：American Astronomical Society

Abstract

We investigated the influence of the Eddington ratio on sub-parsec-scale outflows in active galactic nuclei (AGNs) with supermassive black holes (SMBHs) masses of 107 M ⊙ using two-dimensional radiation hydrodynamics simulations. When the range of the Eddington ratio is γ Edd > 10−3, the radiation force exceeds the gas pressure, leading to stronger outflows and larger dust sublimation radius. Although the sub-parsec-scale outflows are a time-dependent phenomenon, our simulations demonstrated that the radial distributions can be well explained by the steady solutions of the spherically symmetric stellar winds. The dynamic structure of sub-parsec-scale outflows is influenced by the dust sublimation radius and the critical radii determined by the dynamical equilibrium condition. Although significantly affecting the outflow velocity, the Eddington ratio exerts minimal effects on temperature and number density distribution. Furthermore, our analytical solutions highlight the importance of the dust sublimation scale as a crucial determinant of terminal velocity and column density in dusty outflows. Through comparisons of our numerical model with the obscuring fraction observed in nearby AGNs, we reveal insights into the Eddington ratio dependence and the tendency toward the large obscuring fraction of the dusty and dust-free gases. The analytical solutions are expected to facilitate an understanding of the dynamical structure and radiation structures along the line of sight and their viewing angles from observations of ionized outflows.

DOI： 10.3847/1538-4357/ad8b42

その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ad8b42/pdf

Vander Meulen, Bert; Camps, Peter; Tsujimoto, Masahiro; Wada, Keiichi . Intrinsic line profiles for X-ray fluorescent lines in SKIRT . Astronomy & Astrophysics688 L33 - L38 2024年8月査読国際共著

Shunsuke Baba, Keiichi Wada, Takuma Izumi, Yuki Kudoh, Kosei Matsumoto . Circumnuclear Multiphase Gas in the Circinus Galaxy. VI. Detectability of Molecular Inflow and Atomic Outflow . The Astrophysical Journal966 ( 1 ) 15 2024年5月査読国際共著国際誌

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Recent submillimeter observations have revealed signs of pc-scale molecular
inflow and atomic outflow in the nearest Seyfert 2 galaxy, the Circinus galaxy.
To verify the gas kinematics suggested by these observations, we performed
molecular and atomic line transfer calculations based on a physics-based 3D
radiation-hydrodynamic model, which has been compared with multi-wavelength
observations in this paper series. The major axis position-velocity diagram
(PVD) of CO(3-2) reproduces the observed faint emission at the systemic
velocity, and our calculations confirm that this component originates from
failed winds falling back to the disk plane. The minor-axis PVD of
[CI]($^3P_1$-$^3P_0$), when created using only the gas with positive radial
velocities, presents a sign of blue- and redshifted offset peaks similar to
those in the observation, suggesting that the observed peaks indeed originate
from the outflow, but that the model may lack outflows as strong as those in
the Circinus galaxy. Similar to the observed HCN(3-2), the similar dense gas
tracer HCO$^+$(3-2) can exhibit nuclear spectra with inverse P-Cygni profiles
with $\sim$0.5 pc beams, but the line shape is azimuthally dependent. The
corresponding continuum absorbers are inflowing clumps at 5-10 pc from the
center. To detect significant absorption with a high probability, the
inclination must be fairly edge-on ($\gtrsim$85$^\circ$), and the beam size
must be small ($\lesssim$1 pc). These results suggest that HCN or HCO$^+$ and
[CI] lines are effective for observing pc-scale inflows and outflows,
respectively.

DOI： 10.3847/1538-4357/ad34d3

arXiv

Satoshi Yamada, Yoshihiro Ueda, Taiki Kawamuro, Claudio Ricci, Yoshiki Toba, Masatoshi Imanishi, Takamitsu Miyaji, Atsushi Tanimoto, Kohei Ichikawa, Martín Herrera-Endoqui, Shoji Ogawa, Ryosuke Uematsu, Keiichi Wada . [O iv]- and [Ne v]-weak Active Galactic Nuclei Hidden by Compton-thick Material in Late Mergers . Astrophysical Journal965 ( 2 ) 2024年4月

掲載種別：研究論文（学術雑誌）

We study “buried” active galactic nuclei (AGNs) almost fully covered by circumnuclear material in ultra/luminous infrared galaxies (U/LIRGs), which show weak ionized lines from narrow-line regions. Employing an indicator of a [O iv] 25.89 or [Ne v] 14.32 μm line to 12 μm AGN luminosity ratio, we find 17 buried AGN candidates that are [O iv]-weak (L [O IV]/L 12,AGN ≤ −3.0) or [Ne v]-weak (L [Ne V]/L 12,AGN ≤ −3.4) among 30 AGNs in local U/LIRGs. For the [O iv]-weak AGNs, we estimate their covering fractions of Compton-thick (CT; N H ≥ 1024 cm−2) material with an X-ray clumpy torus model to be f CT ( spec ) = 0.55 ± 0.19 on average. This value is consistent with the fraction of CT AGNs ( f CT ( stat ) = 53 % ± 12 % ) among the [O iv]-weak AGNs in U/LIRGs and much larger than that in Swift/Burst Alert Telescope (BAT) AGNs (23% ± 6%). The fraction of [O iv]-weak AGNs increases from 27 − 10 + 13 % (early) to 66 − 12 + 10 % (late mergers). Similar results are obtained with the [Ne v] line. The [O iv]- or [Ne v]-weak AGNs in late mergers show larger N H and Eddington ratios (λ Edd) than those of the Swift/BAT AGNs, and the largest N H is ≳1025 cm−2 at log λ Edd ∼ − 1 , close to the effective Eddington limit for CT material. These suggest that (1) the circumnuclear material in buried AGNs is regulated by the radiation force from high-λ Edd AGNs on the CT obscurers, and (2) their dense material with large f CT ( spec ) (∼0.5 ± 0.1) in U/LIRGs is a likely cause of a unique structure of buried AGNs, whose amount of material may be maintained through merger-induced supply from their host galaxies.

DOI： 10.3847/1538-4357/ad2936

Scopus

Naomichi Yutani, Yoshiki Toba, Keiichi Wada . Apparent Effect of Dust Extinction on the Observed Outflow Velocity of Ionized Gas in Galaxy Mergers . The Astrophysical Journal961 ( 1 ) 68 - 68 2024年1月査読

担当区分：責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：American Astronomical Society

Abstract

In this study, we examine photoionization outflows during the late stages of galaxy mergers, with a specific focus on the relation between the observed velocity of outflowing gas and the apparent effects of dust extinction. We used the N-body/smoothed particle hydrodynamics code ASURA for galaxy merger simulations. These simulations concentrated on identical galaxy mergers featuring supermassive black holes of 108 M ⊙ and gas fractions of 30% and 10%. From the simulation data, we derived velocity and velocity dispersion diagrams for the active galactic nuclei (AGN)-driven ionized outflowing gas. Our findings show that high-velocity outflows with velocity dispersions of 500 km s−1 or greater can be observed in the late stages of galactic mergers. Particularly, in buried AGNs, both the luminosity-weighted outflow velocity and velocity dispersion increase owing to the apparent effects of dust extinction. Owing to these effects, velocity–velocity dispersion diagrams display a noticeable blue-shifted tilt in models with higher gas fractions. Crucially, this tilt is not influenced by the AGN luminosity but emerges from the observational impacts of dust extinction. Our results imply that the observed high-velocity [O iii] λ5007 outflow exceeding 1000 km s−1 in buried AGNs may be linked to the dust extinction that occurs during the late stages of gas-rich galaxy mergers.

DOI： 10.3847/1538-4357/ad0dfc

その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ad0dfc/pdf

Wada, Keiichi; Kudoh, Yuki ; Nagao, Tohru . Multi-phase gas nature in the sub-pc region of the active galactic nuclei II: Possible origins of the changing-state AGNs" . Monthly Notices of the Royal Astronomical Society526 ( 2 ) 2717 - 2723 2023年12月査読

Atsushi Tanimoto, Keiichi Wada, Yuki Kudoh, Hirokazu Odaka, Ryosuke Uematsu, and Shoji Ogawa . Circumnuclear Multi-phase Gas in the Circinus Galaxy. V. The Origin of the X-Ray Polarization in the Circinus Galaxy . The Astrophysical Journal958 150 2023年11月査読

Takuma Izumi, Keiichi Wada, Masatoshi Imanishi, Kouichiro Nakanishi, Kotaro Kohno, Yuki Kudoh, Taiki Kawamuro, Shunsuke Baba, Naoki Matsumoto, Yutaka Fujita, Konrad R. W. Tristram . Supermassive black hole feeding and feedback observed on subparsec scales . Science382 ( 6670 ) 554 - 559 2023年11月査読

掲載種別：研究論文（学術雑誌）出版者・発行元：American Association for the Advancement of Science (AAAS)

Active galaxies contain a supermassive black hole at their center that grows by accreting matter from the surrounding galaxy. The accretion process in about the central 10 parsecs has not been directly resolved in previous observations because of the small apparent angular sizes involved. We observed the active nucleus of the Circinus Galaxy using submillimeter interferometry. A dense inflow of molecular gas was evident on subparsec scales. We calculated that less than 3% of this inflow is accreted by the black hole, with the rest being ejected by multiphase outflows, providing feedback to the host galaxy. Our observations also reveal a dense gas disk surrounding the inflow that is gravitationally unstable, which drives the accretion into about the central 1 parsec.

DOI： 10.1126/science.adf0569

Kosei Matsumoto, Peter Camps, Maarten Baes, Frederik De Ceuster, Keiichi Wada, Takao Nakagawa, Kentaro Nagamine . Self-consistent dust and non-LTE line radiative transfer with SKIRT . Astronomy & Astrophysics 2023年10月査読

Yuki Kudoh, Keiichi Wada, Nozomu Kawakatu, Mariko Nomura . Multiphase Gas Nature in the Sub-parsec Region of the Active Galactic Nuclei. I. Dynamical Structures of Dusty and Dust-free Outflow . The Astrophysical Journal950 ( 1 ) 72 - 72 2023年6月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Astronomical Society

Abstract

We investigated dusty and dust-free gas dynamics for a radiation-driven sub-parsec-scale outflow in an active galactic nucleus (AGN) associated with a supermassive black hole 107M⊙ and bolometric luminosity 1044 erg s−1 based on the two-dimensional radiation-hydrodynamic simulations. A radiation-driven “lotus-like” multi-shell outflow is launched from the inner part (r ≲ 0.04 pc) of the geometrically thin disk, and it repeatedly and steadily produces shocks as mass accretion continues through the disk to the center. The shape of the dust sublimation radius is not spherical and depends on the angle (θ) from the disk plane, reflecting the nonspherical radiation field and nonuniform dust-free gas. Moreover, we found that the sublimation radius of θ ∼ 20°–60° varies on a timescale of several years. The “inflow-induced outflow” contributes to the obscuration of the nucleus in the sub-parsec region. The column density of the dust-free gas is NH ≳ 1022 cm−2 for r ≲ 0.04 pc. Gases near the disk plane (θ ≲ 30°) can be the origin of the Compton-thick component, which was suggested by the recent X-ray observations of AGNs. The dusty outflow from the sub-parsec region can be also a source of material for the radiation-driven fountain for a larger scale.

DOI： 10.3847/1538-4357/accc2b

その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/accc2b/pdf

Naomichi Yutani, Yoshiki Toba, Shunsuke Baba, Keiichi Wada . Origin and Evolution of Dust-obscured Galaxies in Galaxy Mergers . The Astrophysical Journal936 ( 2 ) 118 - 118 2022年9月査読

掲載種別：研究論文（学術雑誌）出版者・発行元：American Astronomical Society

Abstract

Dust-obscured galaxies (DOGs), which are observationally characterized as faint in the optical and bright in the infrared, are the final stage of galaxy mergers and are essential objects in the evolution of galaxies and active galactic nuclei (AGNs). However, the relationship between the torus-scale gas dynamics around AGNs and the DOGs’ lifetime remains unclear. We obtained the evolution of the spectral energy distributions (SEDs) of a galaxy merger system with AGN feedback from postprocessed pseudo-observations based on an N-body/smoothed particle hydrodynamics (SPH) simulation. We focused on a late-stage merger of two identical galaxies with a supermassive black hole (SMBH) of 108M⊙. We found that the infrared luminosity of the system reaches ultra- and hyperluminous infrared galaxy classes (1012 and 1013L⊙, respectively). The DOG phase corresponds to a state in which the AGNs are buried in dense gas and dust, with the infrared luminosity exceeding 3.3 × 1012L⊙. We also identified subcategories of DOGs, namely bump and power-law DOGs, from the SEDs and their evolution. The bump DOGs tend to evolve to power-law DOGs over several Myrs. We found that contribution from the hot dust around the nucleus in the infrared radiation is essential for identifying the system as a power-law DOG; the gas and dust are distributed nonspherically around the nucleus, therefore, the observed properties of DOGs depend on the viewing angle. In our model, the lifetime of merger-driven DOGs is less than 4 Myr, suggesting that the observed DOG phase is a brief aspect of galaxy mergers.

DOI： 10.3847/1538-4357/ac87a2

その他リンク： https://iopscience.iop.org/article/10.3847/1538-4357/ac87a2/pdf

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年7月査読

掲載種別：研究論文（学術雑誌）出版者・発行元：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 θobs = 50°–80°. At the inclination angle θobs = 77°, we observe multi-velocity components: inflow (vLOS = 30 km s−1), systemic (vLOS = 0 km s−1), and outflows (vLOS = −75, − 95, and −105 km s−1). The inflow and outflow components (vLOS = 30 and −95 km s−1) 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

その他リンク： 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年5月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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年2月査読

掲載種別：研究論文（学術雑誌）出版者・発行元：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

その他リンク： 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年1月査読

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年8月国際共著

Kazuma Joh, Tohru Nagao, Keiichi Wada, Koki Terao, Takuji Yamashita . 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年8月査読

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年8月国際共著

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年8月査読国際共著

記述言語：英語掲載種別：研究論文（学術雑誌）

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 870â€† 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 700â€† 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年7月査読国際共著

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年7月査読

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年7月査読

担当区分：責任著者掲載種別：研究論文（学術雑誌）

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年7月査読

掲載種別：研究論文（学術雑誌）

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 . The Astrophysical Journal909 ( 1 ) 96 - 105 2021年3月査読

Wada K. . Nature of inflows and outflows in AGNs . Proceedings of the International Astronomical Union359 297 - 306 2021年招待

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年11月査読

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年10月査読

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年8月査読

Aalto S. . ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377 . Astronomy and Astrophysics640 2020年8月

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年2月査読

Kawaguchi Takeru, Yutani Naomichi, Wada, Keiichi . Mass accretion toward black holes in final phase of galaxy mergers . The Astrophysical Journal890 ( 2 ) 125 - 136 2020年2月査読

Keiichi Wada, Yusuke Tsukamoto, Eiichiro Kokubo . Formation of Planets around Supermassive Black Holes in Active Galactic Nuclei . The Astrophysical Journal 2019年12月

Kudoh Yuki, Wada Keiichi . Magneto Rotational Instability in Magnetized AGN Tori . Galaxies6 ( 4 ) 139 2018年12月査読

記述言語：英語掲載種別：研究論文（学術雑誌）

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年11月査読

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

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年11月査読

記述言語：英語掲載種別：研究論文（学術雑誌）

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年2月査読

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年1月査読

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Schartmann, M.; Mould, J.; Wada, K.; Burkert, A.; Durré, M.; Behrendt, M.; Davies, R. I.; Burtscher, L. . The life cycle of starbursting circumnuclear gas discs . Monthly Notices of the Royal Astronomical Society473 ( 1 ) 953 - 968 2018年1月招待査読

Aalto S. . Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377 . Astronomy and Astrophysics608 2017年12月

Aalto S., Wada, K. 他１３名 . Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377 . Astronomy & Astrophysics 2017年12月招待査読

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年11月査読

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年8月査読

Izumi T. . On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097 . Astrophysical Journal Letters845 ( 1 ) 2017年8月

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年9月

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年1月査読

Keiichi Wada . Obscuring Fraction of Active Galactic Nuclei: Implications from Radiation-driven Fountain Models . The Astrophysical Journal812 82 - 95 2015年10月査読

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年12月査読

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年4月査読

Baba, Junichi; Saitoh, Takayuki R.; Wada, Keiichi . Dynamics of Non-steady Spiral Arms in Disk Galaxies . The Astrophysical Journal763 ( 1 ) 46 - 59 2013年1月査読

Keiichi Wada . Radiation-driven Fountain and Origin of Torus around Active Galactic Nuclei . Astrophysical Journal758 ( 1 ) 66 2012年10月査読

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年8月査読

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年2月査読

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年7月査読

K.Wada, J. Baba, T.R. Saitoh, . Interplay between Stellar Spirals and the ISM in Galactic Disks . The Astrophysical Journal735 1 - 9 2011年7月査読

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年1月査読

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年12月査読

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年12月査読

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年11月査読

Keiichi Wada . Gaseous structure excited by resonances in a non-axisymmetric gravitational potential . 1993年12月

　前のページ - 次のページ　

<和田 桂一>

論文 - 和田 桂一

<和田　桂一>

論文 - 和田　桂一