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Employment (4)

Waseda University: Tokyo, Tokyo, JP

2023-09-01 to present | Associate Professor (Global Center for Science and Engineering, Faculty of Science and Engineering)
Employment
Source: Self-asserted source
Kohei Ichikawa

Tohoku University: Sendai, Miyagi, JP

2018-10-01 to 2023-03-31 | Assistant Professor (Astronomical Institute)
Employment
Source: Self-asserted source
Kohei Ichikawa

Columbia University: New York, NY, US

2016-11-01 to 2018-09-30 | JSPS fellow (Department of Astronomy)
Employment
Source: Self-asserted source
Kohei Ichikawa

National Astronomical Observatory of Japan: Mitaka, Tokyo, JP

2015-04-01 to 2016-03-31 | Postdoctoral fellow (optical and infrared division)
Employment
Source: Self-asserted source
Kohei Ichikawa

Education and qualifications (1)

Kyoto University: Kyoto, Kyoto, JP

2012-04-01 to 2015-03-31 | PhD student (Department of Astronomy)
Education
Source: Self-asserted source
Kohei Ichikawa

Works (47)

Exploring Low-mass Black Holes through Tidal Disruption Events in the Early Universe: Perspectives in the Era of the JWST, Roman Space Telescope, and LSST Surveys

The Astrophysical Journal
2024-05-01 | Journal article
DOI: 10.3847/1538-4357/ad344c
Contributors: Kohei Inayoshi; Kazumi Kashiyama; Wenxiu Li; Yuichi Harikane; Kohei Ichikawa; Masafusa Onoue
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Crossref

[O iv]- and [Ne v]-weak Active Galactic Nuclei Hidden by Compton-thick Material in Late Mergers

The Astrophysical Journal
2024-04-01 | Journal article
DOI: 10.3847/1538-4357/ad2936
Contributors: Satoshi Yamada; Yoshihiro Ueda; Taiki Kawamuro; Claudio Ricci; Yoshiki Toba; Masatoshi Imanishi; Takamitsu Miyaji; Atsushi Tanimoto; Kohei Ichikawa; Martín Herrera-Endoqui et al.
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Crossref

Black Hole Mass and Eddington-ratio Distributions of Less-luminous Quasars at z ∼ 4 in the Subaru Hyper Suprime-Cam Wide Field

The Astrophysical Journal
2024-02-01 | Journal article
DOI: 10.3847/1538-4357/ad1518
Contributors: Wanqiu He; Masayuki Akiyama; Motohiro Enoki; Kohei Ichikawa; Kohei Inayoshi; Nobunari Kashikawa; Toshihiro Kawaguchi; Yoshiki Matsuoka; Tohru Nagao; Masafusa Onoue et al.
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Crossref

Origin of an orbiting star around the galactic supermassive black hole

Proceedings of the Japan Academy, Series B
2024-01-11 | Journal article
DOI: 10.2183/pjab.100.007
Contributors: Shogo NISHIYAMA; Tomohiro KARA; Brian THORSBRO; Hiromi SAIDA; Yohsuke TAKAMORI; Masaaki TAKAHASHI; Takayuki OHGAMI; Kohei ICHIKAWA; Rainer SCHÖDEL
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Crossref

BASS. XLII. The Relation between the Covering Factor of Dusty Gas and the Eddington Ratio in Nearby Active Galactic Nuclei

The Astrophysical Journal
2023-12-01 | Journal article
DOI: 10.3847/1538-4357/ad0733
Contributors: C. Ricci; K. Ichikawa; M. Stalevski; T. Kawamuro; S. Yamada; Y. Ueda; R. Mushotzky; G. C. Privon; M. J. Koss; B. Trakhtenbrot et al.
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Crossref

eROSITA Final Equatorial-Depth Survey (eFEDS)

Astronomy & Astrophysics
2023-04 | Journal article
DOI: 10.1051/0004-6361/202244271
Contributors: Kohei Ichikawa; Takuji Yamashita; Andrea Merloni; Junyao Li; Teng Liu; Mara Salvato; Masayuki Akiyama; Riccardo Arcodia; Tom Dwelly; Xiaoyang Chen et al.
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Crossref

Massive Molecular Gas Companions Uncovered by Very Large Array CO(1–0) Observations of the z = 5.2 Radio Galaxy TN J0924−2201

The Astrophysical Journal
2023-02-01 | Journal article
DOI: 10.3847/1538-4357/acaf58
Contributors: Kianhong Lee; Kotaro Kohno; Bunyo Hatsukade; Fumi Egusa; Takuji Yamashita; Malte Schramm; Kohei Ichikawa; Masatoshi Imanishi; Takuma Izumi; Tohru Nagao et al.
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Crossref

Extreme Nature of Four Blue-excess Dust-obscured Galaxies Revealed by Optical Spectroscopy

The Astrophysical Journal
2022-12-01 | Journal article
DOI: 10.3847/1538-4357/aca403
Contributors: Akatoki Noboriguchi; Tohru Nagao; Yoshiki Toba; Kohei Ichikawa; Masaru Kajisawa; Nanako Kato; Toshihiro Kawaguchi; Hideo Matsuhara; Yoshiki Matsuoka; Kyoko Onishi et al.
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Crossref

H1821+643: The Most X-Ray and Infrared Luminous Active Galactic Nucleus (AGN) in the Swift/BAT Survey in the Process of Rapid Stellar and Supermassive Black Hole Mass Assembly

The Astrophysical Journal
2022-11-01 | Journal article
DOI: 10.3847/1538-4357/ac9304
Contributors: Hikaru Fukuchi; Kohei Ichikawa; Masayuki Akiyama; Claudio Ricci; Sunmyon Chon; Mitsuru Kokubo; Ang Liu; Takuya Hashimoto; Takuma Izumi
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Crossref

BASS XXXII: Studying the Nuclear Millimeter-wave Continuum Emission of AGNs with ALMA at Scales ≲100–200 pc

The Astrophysical Journal
2022-10-01 | Journal article
DOI: 10.3847/1538-4357/ac8794
Contributors: Taiki Kawamuro; Claudio Ricci; Masatoshi Imanishi; Richard F. Mushotzky; Takuma Izumi; Federica Ricci; Franz E. Bauer; Michael J. Koss; Benny Trakhtenbrot; Kohei Ichikawa et al.
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Crossref

Finding of a Population of Active Galactic Nuclei Showing a Significant Luminosity Decline in the Past ∼103–104 yr

The Astrophysical Journal
2022-10-01 | Journal article
DOI: 10.3847/1538-4357/ac8ff3
Contributors: Janek Pflugradt; Kohei Ichikawa; Masayuki Akiyama; Mitsuru Kokubo; Bovornpractch Vijarnwannaluk; Hirofumi Noda; Xiaoyang Chen
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Crossref

Mid-infrared and Maser Flux Variability Correlation in Massive Young Stellar Object G036.70+00.09

The Astrophysical Journal
2022-09-01 | Journal article
DOI: 10.3847/1538-4357/ac866e
Contributors: Mizuho Uchiyama; Kohei Ichikawa; Koichiro Sugiyama; Yoshihiro Tanabe; Yoshinori Yonekura
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Crossref

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). VII. Redshift Evolution of Radio Galaxy Environments at z = 0.3–1.4

The Astrophysical Journal
2022-07-01 | Journal article
DOI: 10.3847/1538-4357/ac77ee
Contributors: Hisakazu Uchiyama; Takuji Yamashita; Tohru Nagao; Kohei Ichikawa; Yoshiki Toba; Shogo Ishikawa; Mariko Kubo; Masaru Kajisawa; Toshihiro Kawaguchi; Nozomu Kawakatu et al.
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Crossref

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). VI. Distant Filamentary Structures Pointed Out by High-z Radio Galaxies at z ∼ 4

The Astrophysical Journal
2022-02-01 | Journal article
DOI: 10.3847/1538-4357/ac441c
Contributors: Hisakazu Uchiyama; Takuji Yamashita; Jun Toshikawa; Nobunari Kashikawa; Kohei Ichikawa; Mariko Kubo; Kei Ito; Nozomu Kawakatu; Tohru Nagao; Yoshiki Toba et al.
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Crossref

Hypercubes of AGN Tori (HYPERCAT). II. Resolving the Torus with Extremely Large Telescopes

The Astrophysical Journal
2021-12-01 | Journal article
DOI: 10.3847/1538-4357/ac2949
Contributors: Robert Nikutta; Enrique Lopez-Rodriguez; Kohei Ichikawa; N. A. Levenson; Christopher Packham; Sebastian F. Hönig; Almudena Alonso-Herrero
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Crossref

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). IV. Rapidly Growing (Super)Massive Black Holes in Extremely Radio-loud Galaxies

The Astrophysical Journal
2021-11-01 | Journal article
DOI: 10.3847/1538-4357/ac1b26
Contributors: Kohei Ichikawa; Takuji Yamashita; Yoshiki Toba; Tohru Nagao; Kohei Inayoshi; Maria Charisi; Wanqiu He; Alexander Y. Wagner; Masayuki Akiyama; Bovornpratch Vijarnwannaluk et al.
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Crossref

Hypercubes of AGN Tori (HYPERCAT). I. Models and Image Morphology

The Astrophysical Journal
2021-10-01 | Journal article
DOI: 10.3847/1538-4357/ac06a6
Contributors: Robert Nikutta; Enrique Lopez-Rodriguez; Kohei Ichikawa; N. A. Levenson; Christopher Packham; Sebastian F. Hönig; Almudena Alonso-Herrero
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Crossref

Cometary records revise Eastern Mediterranean chronology around 1240 CE

Publications of the Astronomical Society of Japan
2021-02-05 | Journal article
DOI: 10.1093/pasj/psaa114
Contributors: Koji Murata; Kohei Ichikawa; Yuri I Fujii; Hisashi Hayakawa; Yongchao Cheng; Yukiko Kawamoto; Hidetoshi Sano
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Crossref

Faint Quasars Live in the Same Number Density Environments as Lyman Break Galaxies at z ∼ 4

The Astrophysical Journal
2020-12-01 | Journal article
DOI: 10.3847/1538-4357/abc47b
Contributors: Hisakazu Uchiyama; Masayuki Akiyama; Jun Toshikawa; Nobunari Kashikawa; Roderik Overzier; Tohru Nagao; Kohei Ichikawa; Murilo Marinello; Masatoshi Imanishi; Masayuki Tanaka et al.
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Crossref

NuSTAR Non-detection of a Faint Active Galactic Nucleus in an Ultraluminous Infrared Galaxy with Kpc-scale Fast Wind

The Astrophysical Journal Letters
2020-12-01 | Journal article
DOI: 10.3847/2041-8213/abca30
Contributors: Xiaoyang Chen; Kohei Ichikawa; Hirofumi Noda; Taiki Kawamuro; Toshihiro Kawaguchi; Yoshiki Toba; Masayuki Akiyama
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Crossref

The Subaru HSC Galaxy Clustering with Photometric Redshift. I. Dark Halo Masses versus Baryonic Properties of Galaxies at 0.3 ≤ z ≤ 1.4

The Astrophysical Journal
2020-12-01 | Journal article
DOI: 10.3847/1538-4357/abbd95
Contributors: Shogo Ishikawa; Nobunari Kashikawa; Masayuki Tanaka; Jean Coupon; Alexie Leauthaud; Jun Toshikawa; Kohei Ichikawa; Taira Oogi; Hisakazu Uchiyama; Yuu Niino et al.
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Crossref

Tracing the Coevolution Path of Supermassive Black Holes and Spheroids with AKARI-selected Ultraluminous IR Galaxies at Intermediate Redshifts

The Astrophysical Journal
2020-09-01 | Journal article
DOI: 10.3847/1538-4357/aba599
Contributors: Xiaoyang Chen; Masayuki Akiyama; Kohei Ichikawa; Hirofumi Noda; Yoshiki Toba; Issei Yamamura; Toshihiro Kawaguchi; Abdurro’ UF; Mitsuru Kokubo
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Crossref

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with the Lyman Break Technique

The Astronomical Journal
2020-08-01 | Journal article
DOI: 10.3847/1538-3881/ab98fe
Contributors: Takuji Yamashita; Tohru Nagao; Hiroyuki Ikeda; Yoshiki Toba; Masaru Kajisawa; Yoshiaki Ono; Masayuki Tanaka; Masayuki Akiyama; Yuichi Harikane; Kohei Ichikawa et al.
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Crossref

Application of an X-Ray Clumpy Torus Model (XCLUMPY) to 10 Obscured Active Galactic Nuclei Observed with Suzaku and NuSTAR

The Astrophysical Journal
2020-07-01 | Journal article
DOI: 10.3847/1538-4357/ab96bc
Contributors: Atsushi Tanimoto; Yoshihiro Ueda; Hirokazu Odaka; Shoji Ogawa; Satoshi Yamada; Toshihiro Kawaguchi; Kohei Ichikawa
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Crossref

The BAT AGN Spectroscopic Survey. XVIII. Searching for Supermassive Black Hole Binaries in X-Rays

The Astrophysical Journal
2020-06-01 | Journal article
DOI: 10.3847/1538-4357/ab952d
Contributors: Tingting Liu; Michael Koss; Laura Blecha; Claudio Ricci; Benny Trakhtenbrot; Richard Mushotzky; Fiona Harrison; Kohei Ichikawa; Darshan Kakkad; Kyuseok Oh et al.
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Crossref

Universal Transition Diagram from Dormant to Actively Accreting Supermassive Black Holes

The Astrophysical Journal
2020-05-01 | Journal article
DOI: 10.3847/1538-4357/ab8569
Contributors: Kohei Inayoshi; Kohei Ichikawa; Luis C. Ho
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Crossref

ALMA Polarimetry Measures Magnetically Aligned Dust Grains in the Torus of NGC 1068

The Astrophysical Journal
2020-04-01 | Journal article
DOI: 10.3847/1538-4357/ab8013
Contributors: Enrique Lopez-Rodriguez; Almudena Alonso-Herrero; Santiago García-Burillo; Michael S. Gordon; Kohei Ichikawa; Masatoshi Imanishi; Seiji Kameno; Nancy A. Levenson; Robert Nikutta; Chris Packham
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Crossref

Dust Destruction by Charging: A Possible Origin of Gray Extinction Curves of Active Galactic Nuclei

The Astrophysical Journal
2020-04-01 | Journal article
DOI: 10.3847/1538-4357/ab7822
Contributors: Ryo Tazaki; Kohei Ichikawa; Mitsuru Kokubo
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Crossref

Dust Destruction by Drift-induced Sputtering in Active Galactic Nuclei

The Astrophysical Journal
2020-04-01 | Journal article
DOI: 10.3847/1538-4357/ab72f6
Contributors: Ryo Tazaki; Kohei Ichikawa
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Crossref

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

The Astrophysical Journal
2020-02-01 | Journal article
DOI: 10.3847/1538-4357/ab5f60
Contributors: Nozomu Kawakatu; Keiichi Wada; Kohei Ichikawa
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Crossref

Obscuring fraction of active galactic nuclei implied by supernova and radiative feedbacks

arXiv e-prints
2019-12 | Working paper
BIBCODE: 2019arXiv191202408K
ARXIV: 1912.02408
Contributors: Kawakatu, Nozomu; Wada, Keiichi; Ichikawa, Kohei
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NASA Astrophysics Data System

The BAT AGN Spectroscopic Survey -- XVIII. Searching for Supermassive Black Hole Binaries in the X-rays

arXiv e-prints
2019-12 | Working paper
BIBCODE: 2019arXiv191202837L
ARXIV: 1912.02837
Contributors: Liu, Tingting; Koss, Michael; Blecha, Laura; Ricci, Claudio; Trakhtenbrot, Benny; Mushotzky, Richard; Harrison, Fiona; Ichikawa, Kohei; Kakkad, Darshan; Oh, Kyuseok et al.
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NASA Astrophysics Data System

BAT AGN Spectroscopic Survey - XIII. The nature of the most luminous obscured AGN in the low-redshift universe

Monthly Notices of the Royal Astronomical Society
2019-11 | Journal article
DOI: 10.1093/mnras/stz2309
BIBCODE: 2019MNRAS.489.3073B
ARXIV: 1908.07546
Contributors: Bär, Rudolf E.; Trakhtenbrot, Benny; Oh, Kyuseok; Koss, Michael J.; Wong, O. Ivy; Ricci, Claudio; Schawinski, Kevin; Weigel, Anna K.; Sartori, Lia F.; Ichikawa, Kohei et al.
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NASA Astrophysics Data System

NuSTAR Discovery of Dead Quasar Engine in Arp 187

The Astrophysical Journal Letters
2019-09-20 | Journal article
DOI: 10.3847/2041-8213/ab3ebf
Contributors: Kohei Ichikawa; Taiki Kawamuro; Megumi Shidatsu; Claudio Ricci; Hyun-Jin Bae; Kenta Matsuoka; Jaejin Shin; Yoshiki Toba; Junko Ueda; Yoshihiro Ueda
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Crossref

WISE Discovery of Mid-infrared Variability in Massive Young Stellar Objects

The Astrophysical Journal
2019-09-20 | Journal article
DOI: 10.3847/1538-4357/ab372e
Contributors: Mizuho Uchiyama; Kohei Ichikawa
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Crossref

A NuSTAR and XMM-Newton Study of the Two Most Actively Star-forming Green Pea Galaxies (SDSS J0749+3337 and SDSS J0822+2241)

The Astrophysical Journal
2019-08-10 | Journal article
DOI: 10.3847/1538-4357/ab2bf6
Contributors: Taiki Kawamuro; Yoshihiro Ueda; Kohei Ichikawa; Masatoshi Imanishi; Takuma Izumi; Atsushi Tanimoto; Kenta Matsuoka
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Crossref

A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). II. Physical Properties Derived from the SED Fitting with Optical, Infrared, and Radio Data

The Astrophysical Journal Supplement Series
2019-07-01 | Journal article
DOI: 10.3847/1538-4365/ab238d
Contributors: Yoshiki Toba; Takuji Yamashita; Tohru Nagao; Wei-Hao Wang; Yoshihiro Ueda; Kohei Ichikawa; Toshihiro Kawaguchi; Masayuki Akiyama; Bau-Ching Hsieh; Masaru Kajisawa et al.
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Crossref

Discovery of Dying Active Galactic Nucleus in Arp 187: Experience of Drastic Luminosity Decline within 104 yr

The Astrophysical Journal
2019-01-10 | Journal article
DOI: 10.3847/1538-4357/aaf233
Contributors: Kohei Ichikawa; Junko Ueda; Hyun-Jin Bae; Taiki Kawamuro; Kenta Matsuoka; Yoshiki Toba; Megumi Shidatsu
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Crossref

BAT AGN Spectroscopic Survey. XI. The Covering Factor of Dust and Gas in Swift/BAT Active Galactic Nuclei

The Astrophysical Journal
2019-01-01 | Journal article
DOI: 10.3847/1538-4357/aaef8f
Contributors: Kohei Ichikawa; Claudio Ricci; Yoshihiro Ueda; Franz E. Bauer; Taiki Kawamuro; Michael J. Koss; Kyuseok Oh; David J. Rosario; T. Taro Shimizu; Marko Stalevski et al.
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Crossref

The origin of the mid-infrared nuclear polarization of active galactic nuclei

Monthly Notice of Royal Astronomical Society
2018-08 | Journal article
DOI: 10.1093/mnras/sty1197
Source: Self-asserted source
Kohei Ichikawa

Gravitational Waves from Supermassive Black Hole Binaries in Ultraluminous Infrared Galaxies

The Astrophysical Journal Letters
2018-08-20 | Journal article
DOI: 10.3847/2041-8213/aad8ad
Contributors: Kohei Inayoshi; Kohei Ichikawa; Zoltán Haiman
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Crossref

The Emission and Distribution of Dust of the Torus of NGC 1068

The Astrophysical Journal
2018-06-01 | Journal article
DOI: 10.3847/1538-4357/aabd7b
Contributors: Enrique Lopez-Rodriguez; Lindsay Fuller; Almudena Alonso-Herrero; Andreas Efstathiou; Kohei Ichikawa; Nancy A. Levenson; Chris Packham; James Radomski; Cristina Ramos Almeida; Dominic J. Benford et al.
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Crossref

NuSTAR Hard X-Ray Data and Gemini 3D Spectra Reveal Powerful AGN and Outflow Histories in Two Low-redshift Lyα Blobs

The Astrophysical Journal
2017-10-10 | Journal article
DOI: 10.3847/1538-4357/aa8e46
Contributors: Taiki Kawamuro; Mischa Schirmer; James E. H. Turner; Rebecca L. Davies; Kohei Ichikawa
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Crossref

Cooling Timescale of Dust Tori in Dying Active Galactic Nuclei

The Astrophysical Journal
2017-07-20 | Journal article
DOI: 10.3847/1538-4357/aa7891
Contributors: Kohei Ichikawa; Ryo Tazaki
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Crossref

[O iii]λ5007 AND X-RAY PROPERTIES OF A COMPLETE SAMPLE OF HARD X-RAY SELECTED AGNs IN THE LOCAL UNIVERSE

The Astrophysical Journal
2015-12-02 | Journal article
DOI: 10.1088/0004-637X/815/1/1
Contributors: Y. Ueda; Y. Hashimoto; K. Ichikawa; Y. Ishino; A. Y. Kniazev; P. Väisänen; C. Ricci; S. Berney; P. Gandhi; M. Koss et al.
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Crossref

THE DIFFERENCES IN THE TORUS GEOMETRY BETWEEN HIDDEN AND NON-HIDDEN BROAD LINE ACTIVE GALACTIC NUCLEI

The Astrophysical Journal
2015-04-15 | Journal article
DOI: 10.1088/0004-637X/803/2/57
Contributors: Kohei Ichikawa; Christopher Packham; Cristina Ramos Almeida; Andrés Asensio Ramos; Almudena Alonso-Herrero; Omaira González-Martín; Enrique Lopez-Rodriguez; Yoshihiro Ueda; Tanio Díaz-Santos; Moshe Elitzur et al.
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Crossref

AKARI IRC 2.5-5 μm Spectroscopy of Infrared Galaxies over a Wide Luminosity Range

2014-10-01 | Journal article
Source: Self-asserted source
Kohei Ichikawa
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