Updated on 2024/04/16

写真a

 
SHIMONISHI Takashi
 
Organization
Academic Assembly Institute of Science and Technology CHIKYU SEIBUTSU KAGAKU KEIRETU Associate Professor
Graduate School of Science and Technology Environmental Science and Technology Associate Professor
Faculty of Science Department of Science Associate Professor
Title
Associate Professor
External link

Degree

  • 博士(理学) ( 2012.3   東京大学 )

  • 修士(理学) ( 2009.3   東京大学 )

Research Interests

  • Outer Galaxy

  • James Webb Space Telescope

  • Metallicity

  • Astrochemistry

  • Interstellar molecule

  • Interstellar ice

  • Magellanic Clouds

  • Hot molecular core

  • Star Formation

  • あかり衛星

  • ALMA

  • Radio Astronomy

  • Infrared Astronomy

  • Interstellar Medium

Research Areas

  • Natural Science / Space and planetary sciences

  • Natural Science / Astronomy

Research History (researchmap)

  • Niigata University   Environmental Science Program, Faculty of Science, Department of Science   Associate Professor

    2022.4

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  • Niigata University   Graduate School of Science and Technology, Specialized Course of Environmental Science and Technology   Associate Professor

    2022.4

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  • Niigata University   Institute for Research Promotion Center for Transdisciplinary Research   Assistant Professor

    2019.11 - 2022.3

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  • Tohoku University   Frontier Research Institute for Interdisciplinary Sciences   Assistant Professor

    2015.1 - 2019.10

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  • Kobe University   Graduate School of Science, Division of Earth and Planetary Sciences

    2012.4 - 2014.12

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  • The University of Tokyo   Graduate School of Science, Department of Astronomy

    2010.4 - 2012.3

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Research History

  • Niigata University   Environmental Science and Technology, Graduate School of Science and Technology   Associate Professor

    2022.4

  • Niigata University   Faculty of Science   Associate Professor

    2022.4

  • Niigata University   Institute of Science and Technology, Academic Assembly   Associate Professor

    2022.4

  • Niigata University   Institute for Research Promotion, Center for Transdisciplinary Research

    2021.8 - 2022.3

  • Niigata University   Institute for Research Promotion, Center for Transdisciplinary Research   Assistant Professor

    2019.11 - 2022.3

Education

  • The University of Tokyo   Graduate School of Science   Department of Astronomy

    2009.4 - 2012.3

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  • The University of Tokyo   Graduate School of Science   Department of Astronomy

    2007.4 - 2009.3

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  • Tohoku University   Faculty of Science   Department of Astronomy and Geophysics

    2003.4 - 2007.3

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Professional Memberships

 

Papers

  • Spectroscopic sizing of interstellar icy grains with JWST Reviewed

    E. Dartois, J. A. Noble, P. Caselli, H. J. Fraser, I. Jiménez-Serra, B. Maté, M. K. McClure, G. J. Melnick, Y. J. Pendleton, T. Shimonishi, Z. L. Smith, J. A. Sturm, A. Taillard, V. Wakelam, A. C. A. Boogert, M. N. Drozdovskaya, J. Erkal, D. Harsono, V. J. Herrero, S. Ioppolo, H. Linnartz, B. A. McGuire, G. Perotti, D. Qasim, W. R. M. Rocha

    Nature Astronomy   2024.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41550-023-02155-x

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    Other Link: https://www.nature.com/articles/s41550-023-02155-x

  • Chemical Evolution of Some Selected Complex Organic Molecules in Low-mass Star-forming Regions Reviewed

    Bratati Bhat, Rumela Kar, Suman Kumar Mondal, Rana Ghosh, Prasanta Gorai, Takashi Shimonishi, Kei E. I. Tanaka, Kenji Furuya, Ankan Das

    The Astrophysical Journal   958 ( 2 )   111 - 111   2023.11

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

    Abstract

    The destiny of complex organic molecules (COMs) in star-forming regions is interlinked with various evolutionary phases. Therefore, identifying these species in diversified environments of identical star-forming regions would help to understand their physical and chemical heritage. We identified multiple COMs utilizing the Large Program Astrochemical Surveys At Institut de Radio Astronomie Millimétrique (IRAM) data, dedicated to chemical surveys in Sun-like star-forming regions with the IRAM 30 m telescope. It was an unbiased survey in the millimeter regime, covering the prestellar core, protostar, outflow region, and protoplanetary disk phase. Here, we report the transitions of seven COMs, namely, methanol (CH<sub>3</sub>OH), acetaldehyde (CH<sub>3</sub>CHO), methyl formate (CH<sub>3</sub>OCHO), ethanol (C<sub>2</sub>H<sub>5</sub>OH), propynal (HCCCHO), dimethyl ether (CH<sub>3</sub>OCH<sub>3</sub>), and methyl cyanide (CH<sub>3</sub>CN) in sources L1544, B1-b, IRAS4A, and SVS13A. We found a trend among these species from the derived abundances using the rotational diagram method and Monte Carlo Markov chain fitting. We have found that the abundances of all of the COMs, except for HCCCHO, increase from the L1544 (prestellar core) and peaks at IRAS16293-2422 (class 0 phase). It is noticed that the abundance of these molecules correlates with the luminosity of the sources. The obtained trend is also visible from the previous interferometric observations and considering the beam dilution effect.

    DOI: 10.3847/1538-4357/acfc4d

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/acfc4d/pdf

  • An ALMA Glimpse of Dense Molecular Filaments Associated with High-mass Protostellar Systems in the Large Magellanic Cloud

    Kazuki Tokuda, Naoto Harada, Kei E. I. Tanaka, Tsuyoshi Inoue, Takashi Shimonishi, Yichen Zhang, Marta Sewiło, Yuri Kunitoshi, Ayu Konishi, Yasuo Fukui, Akiko Kawamura, Toshikazu Onishi, Masahiro N. Machida

    The Astrophysical Journal   955 ( 1 )   52 - 52   2023.9

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

    Abstract

    Recent millimeter/submillimeter facilities have revealed the physical properties of filamentary molecular clouds in relation to high-mass star formation. A uniform survey of the nearest, face-on star-forming galaxy, the Large Magellanic Cloud (LMC), complements the Galactic knowledge. We present ALMA survey data with a spatial resolution of ∼0.1 pc in the 0.87 mm continuum and HCO<sup>+</sup> (4–3) emission toward 30 protostellar objects with luminosities of 10<sup>4</sup>–10<sup>5.5</sup>L<sub>⊙</sub> in the LMC. The spatial distributions of the HCO<sup>+</sup> (4–3) line and thermal dust emission are well correlated, indicating that the line effectively traces dense, filamentary gas with an H<sub>2</sub> volume density of ≳10<sup>5</sup> cm<sup>−3</sup> and a line mass of ∼10<sup>3</sup>–10<sup>4</sup>M<sub>⊙</sub> pc<sup>−1</sup>. Furthermore, we obtain an increase in the velocity line widths of filamentary clouds, which follows a power-law dependence on their H<sub>2</sub> column densities with an exponent of ∼0.5. This trend is consistent with observations toward filamentary clouds in nearby star-forming regions within ≲1 kpc from us and suggests enhanced internal turbulence within the filaments due to surrounding gas accretion. Among the 30 sources, we find that 14 are associated with hub-filamentary structures, and these complex structures predominantly appear in protostellar luminosities exceeding ∼5 × 10<sup>4</sup>L<sub>⊙</sub>. The hub-filament systems tend to appear in the latest stages of their natal cloud evolution, often linked to prominent H ii regions and numerous stellar clusters. Our preliminary statistics suggest that the massive filaments accompanied by hub-type complex features may be a necessary intermediate product in forming extremely luminous high-mass stellar systems capable of ultimately dispersing the parent cloud.

    DOI: 10.3847/1538-4357/acefb7

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/acefb7/pdf

  • Cosmic-ray-driven enhancement of the C0/CO abundance ratio in W 51 C Reviewed

    Mitsuyoshi Yamagishi, Kenji Furuya, Hidetoshi Sano, Natsuko Izumi, Tatsuya Takekoshi, Hidehiro Kaneda, Kouichiro Nakanishi, Takashi Shimonishi

    Publications of the Astronomical Society of Japan   2023.7

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    DOI: 10.1093/pasj/psad046

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  • The Detection of Hot Molecular Cores in the Small Magellanic Cloud Reviewed

    Takashi Shimonishi, Kei E. I. Tanaka, Yichen Zhang, Kenji Furuya

    The Astrophysical Journal Letters   946 ( L41 )   1 - 14   2023.4

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

    DOI: 10.3847/2041-8213/acc031

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  • An Ice Age JWST inventory of dense molecular cloud ices Reviewed

    M. K. McClure, W. R. M. Rocha, K. M. Pontoppidan, N. Crouzet, L. E. U. Chu, E. Dartois, T. Lamberts, J. A. Noble, Y. J. Pendleton, G. Perotti, D. Qasim, M. G. Rachid, Z. L. Smith, Fengwu Sun, Tracy L. Beck, A. C. A. Boogert, W. A. Brown, P. Caselli, S. B. Charnley, Herma M. Cuppen, H. Dickinson, M. N. Drozdovskaya, E. Egami, J. Erkal, H. Fraser, R. T. Garrod, D. Harsono, S. Ioppolo, I. Jiménez-Serra, M. Jin, J. K. Jørgensen, L. E. Kristensen, D. C. Lis, M. R. S. McCoustra, Brett A. McGuire, G. J. Melnick, Karin I. Öberg, M. E. Palumbo, T. Shimonishi, J. A. Sturm, E. F. van Dishoeck, H. Linnartz

    Nature Astronomy   2023.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41550-022-01875-w

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    Other Link: https://www.nature.com/articles/s41550-022-01875-w

  • Near-infrared Spectroscopy of a Massive Young Stellar Object in the Direction toward the Galactic Center: XCN and Aromatic C–D Features Reviewed

    Takashi Onaka, Itsuki Sakon, Takashi Shimonishi

    The Astrophysical Journal   941 ( 2 )   190 - 190   2022.12

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

    Abstract

    We report near-infrared (2.5–5 μm) long-slit (∼30″) spectroscopy of a young stellar object in the direction toward the Galactic center with the Infrared Camera on board the AKARI satellite. The present target is suggested to be AFGL 2006 based on its very red color and close location. The spectra show strong absorption features of H<sub>2</sub>O and CO<sub>2</sub> ices, and emission of H i Brα recombination line and the 3.3 μm band, the latter of which originates from polycyclic aromatic hydrocarbons (PAHs) or materials containing PAHs. The spectra show a broad, complex absorption feature at 4.65 μm, which is well explained by a combination of absorption features of CO ice, CO gas, and XCN, and H i Pfβ emission. The spectra also indicate excess emission at 4.4 μm. The characteristics of the spectra suggest that the object is a massive young stellar object. The XCN feature shows a good correlation with the Brα emission, suggesting that the photolysis by ultraviolet photons plays an important role in the formation of the XCN carriers, part of which are attributed to OCN<sup>−</sup>. The 4.4 μm emission shows a good correlation with the 3.3 μm PAH emission, providing supporting evidence that it comes from the aromatic C–D stretching vibration. The formation of OCN<sup>−</sup> is of importance for the formation process of prebiotic matter in the interstellar medium (ISM), while the detection of aromatic C–D emission provides valuable information on the deuteration process of PAHs in the ISM and implications on the hiding site of the missing deuterium in the ISM.

    DOI: 10.3847/1538-4357/ac9b15

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac9b15/pdf

  • The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA Reviewed

    Kazuki Tokuda, Sarolta Zahorecz, Yuri Kunitoshi, Kosuke Higashino, Kei E. I. Tanaka, Ayu Konishi, Taisei Suzuki, Naoya Kitano, Naoto Harada, Takashi Shimonishi, Naslim Neelamkodan, Yasuo Fukui, Akiko Kawamura, Toshikazu Onishi, Masahiro N. Machida

    The Astrophysical Journal Letters   936 ( 1 )   L6 - L6   2022.9

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

    Abstract

    Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z<sub>⊙</sub>, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3–2) emission at ≳15 km s<sup>−1</sup>. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ∼0.2–1 Z<sub>⊙</sub>.

    DOI: 10.3847/2041-8213/ac81c1

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    Other Link: https://iopscience.iop.org/article/10.3847/2041-8213/ac81c1/pdf

  • Chiral Ice Crystals in Space Reviewed

    Akira Kouchi, Takashi Shimonishi, Tomoya Yamazaki, Masashi Tsuge, Naoki Nakatani, Kenji Furuya, Hiromasa Niinomi, Yasuhiro Oba, Tetsuya Hama, Hiroyasu Katsuno, Naoki Watanabe, Yuki Kimura

    Chirality - New Insights [Working Title]   2022.8

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    Language:English   Publishing type:Part of collection (book)   Publisher:IntechOpen  

    We observed the formation of CO, CH3OH, and H2O ices using a cryogenic transmission electron microscope, to determine if chiral ice crystals could form under the conditions of interstellar molecular clouds and young stellar objects (protoplanetary disks) and to clarify the crystalline structure of these ices. Our results suggest that the following ice crystals are chiral: crystalline CO (α-CO) formed on amorphous H2O (a-H2O) grains in a 10-K molecular cloud, crystalline CH3OH formed by the heating of amorphous CH3OH on a-H2O grains at 40–60 K in young stellar objects, and several polymorphs of hydrogen-ordered cubic ice crystals formed by the heating of a-H2O at 80–100 K and direct condensation at 120–140 K in protoplanetary disks. We also investigated candidates for other chiral ices using published data. We found that NH3 I and NH3·H2O I are chiral at low temperature and pressure conditions. If one-handed circularly polarized light is irradiated during the nucleation of these chiral ice crystals, homochiral crystals can be formed. These results have important implications for the origin of interstellar organic molecule homochirality.

    DOI: 10.5772/intechopen.106708

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  • Quantifying the Chemical Desorption of H<sub>2</sub>S and PH<sub>3</sub> from Amorphous Water-ice Surfaces Reviewed

    Kenji Furuya, Yasuhiro Oba, Takashi Shimonishi

    The Astrophysical Journal   926 ( 2 )   171 - 171   2022.2

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

    Abstract

    Nonthermal desorption of molecules from icy grain surfaces is required to explain molecular line observations in the cold gas of star-forming regions. Chemical desorption is one of the nonthermal desorption processes and is driven by the energy released by chemical reactions. After an exothermic surface reaction, the excess energy is transferred to products’ translational energy in the direction perpendicular to the surface, leading to desorption. The desorption probability of product species, especially that of product species from water-ice surfaces, is not well understood. This uncertainty limits our understanding of the interplay between gas-phase and ice-surface chemistry. In the present work, we constrain the desorption probability of H<sub>2</sub>S and PH<sub>3</sub> per reaction event on porous amorphous solid water (ASW) by numerically simulating previous laboratory experiments. Adopting the microscopic kinetic Monte Carlo method, we find that the desorption probabilities of H<sub>2</sub>S and PH<sub>3</sub> from porous ASW per hydrogen-addition event of the precursor species are 3% ± 1.5% and 4% ± 2%, respectively. These probabilities are consistent with a theoretical model of chemical desorption proposed in the literature if ∼7% of energy released by the reactions is transferred to the translational excitation of the products. As a byproduct, we find that approximately 70% (40%) of adsorption sites for atomic H on porous ASW should have a binding energy lower than ∼300 K (∼200 K). The astrochemical implications of our findings are briefly discussed.

    DOI: 10.3847/1538-4357/ac4260

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac4260/pdf

  • Is There Any Linkage between Interstellar Aldehyde and Alcohol? Reviewed

    Suman Kumar Mondal, Prasanta Gorai, Milan Sil, Rana Ghosh, Emmanuel E. Etim, Sandip K. Chakrabarti, Takashi Shimonishi, Naoki Nakatani, Kenji Furuya, Jonathan C. Tan, Ankan Das

    The Astrophysical Journal   922 ( 2 )   194 - 194   2021.12

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

    <title>Abstract</title>
    It is speculated that there might be some linkage between interstellar aldehydes and their corresponding alcohols. Here an observational study and astrochemical modeling are coupled together to illustrate the connection between them. The ALMA cycle 4 data of a hot molecular core, G10.47+0.03, are utilized for this study. Various aldehydes (acetaldehyde, propanal, and glycolaldehyde), alcohols (methanol and ethylene glycol), and a ketone (acetone) are identified in this source. The excitation temperatures and column densities of these species were derived via the rotation diagram method assuming local thermodynamic equilibrium conditions. An extensive investigation is carried out to understand the formation of these species. Six pairs of aldehyde–alcohol are considered for this study: (i) methanal and methanol, (ii) ethanal and ethanol, (iii) propanal and 1-propanol, (iv) propenal and allyl alcohol, (v) propynal and propargyl alcohol, and (vi) glycolaldehyde and ethylene glycol. One pair of ketone–alcohol (acetone and isopropanol) and ketene–alcohol (ethenone and vinyl alcohol) are also considered. Two successive hydrogenation reactions in the ice phase are examined to form these alcohols from aldehydes, ketone, and ketene, respectively. Quantum chemical methods are extensively executed to review the ice-phase formation route and the kinetics of these species. Based on the obtained kinetic data, astrochemical modeling is employed to derive the abundances of these aldehydes, alcohols, ketone, and ketene in this source. It is seen that our model could successfully explain the observed abundances of various species in this hot molecular core.

    DOI: 10.3847/1538-4357/ac1f31

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac1f31/pdf

  • The Detection of a Hot Molecular Core in the Extreme Outer Galaxy Reviewed

    Takashi Shimonishi, Natsuko Izumi, Kenji Furuya, Chikako Yasui

    The Astrophysical Journal   922 ( 2 )   206 - 206   2021.12

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

    <title>Abstract</title>
    Interstellar chemistry in low-metallicity environments is crucial to understand chemical processes in the past metal-poor universe. Recent studies of interstellar molecules in nearby low-metallicity galaxies have suggested that metallicity has a significant effect on the chemistry of star-forming cores. Here we report the first detection of a hot molecular core in the extreme outer Galaxy, which is an excellent laboratory to study star formation and the interstellar medium in a Galactic low-metallicity environment. The target star-forming region, WB 89–789, is located at a galactocentric distance of 19 kpc. Our Atacama Large Millimeter/submillimeter Array observations in 241–246, 256–261, 337–341, and 349–353 GHz have detected a variety of carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing species, including complex organic molecules (COMs) containing up to nine atoms, toward a warm (&gt;100 K) and compact (&lt;0.03 pc) region associated with a protostar (∼8 × 10<sup>3</sup>
    <italic>L</italic>
    <sub>☉</sub>). Deuterated species such as HDO, HDCO, D<sub>2</sub>CO, and CH<sub>2</sub>DOH are also detected. A comparison of fractional abundances of COMs relative to CH<sub>3</sub>OH between the outer Galactic hot core and an inner Galactic counterpart shows a remarkable similarity. On the other hand, the molecular abundances in the present source do not resemble those of low-metallicity hot cores in the Large Magellanic Cloud. The results suggest that great molecular complexity exists even in the primordial environment of the extreme outer Galaxy. The detection of another embedded protostar associated with high-velocity SiO outflows is also reported.

    DOI: 10.3847/1538-4357/ac289b

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac289b/pdf

  • The formation of planetary systems with SPICA Reviewed

    I. Kamp, M. Honda, H. Nomura, M. Audard, D. Fedele, L. B. F. M. Waters, Y. Aikawa, A. Banzatti, J.E. Bowey, M. Bradford, C. Dominik, K. Furuya, E. Habart, D. Ishihara, D. Johnstone, G. Kennedy, M. Kim, Q. Kral, S.-P. Lai, B. Larsson, M. McClure, A. Miotello, M. Momose, T. Nakagawa, D. Naylor, B. Nisini, S. Notsu, T. Onaka, E. Pantin, L. Podio, P. Riviere Marichalar, W. R. M. Rocha, P. Roelfsema, T. Shimonishi, Y.-W. Tang, M. Takami, R. Tazaki, S. Wolf, M. Wyatt, N. Ysard

    Publications of the Astronomical Society of Australia   38   2021.11

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    Publishing type:Research paper (scientific journal)   Publisher:Cambridge University Press (CUP)  

    <title>Abstract</title>
    In this era of spatially resolved observations of planet-forming disks with Atacama Large Millimeter Array (ALMA) and large ground-based telescopes such as the Very Large Telescope (VLT), Keck, and Subaru, we still lack statistically relevant information on the quantity and composition of the material that is building the planets, such as the total disk gas mass, the ice content of dust, and the state of water in planetesimals. <italic>SPace Infrared telescope for Cosmology and Astrophysics (SPICA)</italic> is an infrared space mission concept developed jointly by Japan Aerospace Exploration Agency (JAXA) and European Space Agency (ESA) to address these questions. The key unique capabilities of <italic>SPICA</italic> that enable this research are (1) the wide spectral coverage <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline1.png" />
    <tex-math>
    $10{-}220\,\mu\mathrm{m}$
    </tex-math>
    </alternatives>
    </inline-formula>, (2) the high line detection sensitivity of <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline2.png" />
    <tex-math>
    $(1{-}2) \times 10^{-19}\,\mathrm{W\,m}^{-2}$
    </tex-math>
    </alternatives>
    </inline-formula> with <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline3.png" />
    <tex-math>
    $R \sim 2\,000{-}5\,000$
    </tex-math>
    </alternatives>
    </inline-formula> in the far-IR (SAFARI), and <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline4.png" />
    <tex-math>
    $10^{-20}\,\mathrm{W\,m}^{-2}$
    </tex-math>
    </alternatives>
    </inline-formula> with <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline5.png" />
    <tex-math>
    $R \sim 29\,000$
    </tex-math>
    </alternatives>
    </inline-formula> in the mid-IR (<italic>SPICA</italic> Mid-infrared Instrument (SMI), spectrally resolving line profiles), (3) the high far-IR continuum sensitivity of 0.45 mJy (SAFARI), and (4) the observing efficiency for point source surveys. This paper details how mid- to far-IR infrared spectra will be unique in measuring the gas masses and water/ice content of disks and how these quantities evolve during the planet-forming period. These observations will clarify the crucial transition when disks exhaust their primordial gas and further planet formation requires secondary gas produced from planetesimals. The high spectral resolution mid-IR is also unique for determining the location of the snowline dividing the rocky and icy mass reservoirs within the disk and how the divide evolves during the build-up of planetary systems. Infrared spectroscopy (mid- to far-IR) of key solid-state bands is crucial for assessing whether extensive radial mixing, which is part of our Solar System history, is a general process occurring in most planetary systems and whether extrasolar planetesimals are similar to our Solar System comets/asteroids. We demonstrate that the SPICA mission concept would allow us to achieve the above ambitious science goals through large surveys of several hundred disks within <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S132335802100031X_inline6.png" />
    <tex-math>
    $\sim\!2.5$
    </tex-math>
    </alternatives>
    </inline-formula> months of observing time.

    DOI: 10.1017/pasa.2021.31

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  • Transmission Electron Microscopy Study of the Morphology of Ices Composed of H2O, CO2, and CO on Refractory Grains Reviewed

    Akira Kouchi, Masashi Tsuge, Tetsuya Hama, Yasuhiro Oba, Satoshi Okuzumi, Sin-iti Sirono, Munetake Momose, Naoki Nakatani, Kenji Furuya, Takashi Shimonishi, Tomoya Yamazaki, Hiroshi Hidaka, Yuki Kimura, Ken-ichiro Murata, Kazuyuki Fujita, Shunichi Nakatsubo, Shogo Tachibana, Naoki Watanabe

    The Astrophysical Journal   918 ( 2 )   45 - 45   2021.9

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

    DOI: 10.3847/1538-4357/ac0ae6

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/ac0ae6/pdf

  • Chemical Complexity of Phosphorous-bearing Species in Various Regions of the Interstellar Medium Reviewed

    Milan Sil, Satyam Srivastav, Bratati Bhat, Suman Kumar Mondal, Prasanta Gorai, Rana Ghosh, Takashi Shimonishi, Sandip K. Chakrabarti, Bhalamurugan Sivaraman, Amit Pathak, Naoki Nakatani, Kenji Furuya, Ankan Das

    ASTRONOMICAL JOURNAL   162 ( 3 )   2021.9

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    Phosphorus-related species are not known to be as omnipresent in space as hydrogen, carbon, nitrogen, oxygen, and sulfur-bearing species. Astronomers spotted very few P-bearing molecules in the interstellar medium and circumstellar envelopes. Limited discovery of the P-bearing species imposes severe constraints in modeling the P-chemistry. In this paper, we carry out extensive chemical models to follow the fate of P-bearing species in diffuse clouds, photon-dominated or photodissociation regions (PDRs), and hot cores/corinos. We notice a curious correlation between the abundances of PO and PN and atomic nitrogen. Since N atoms are more abundant in diffuse clouds and PDRs than in the hot core/corino region, PO/PN reflects <1 in diffuse clouds, MUCH LESS-THAN1 in PDRs, and >1 in the late warm-up evolutionary stage of the hot core/corino regions. During the end of the post-warm-up stage, we obtain PO/PN > 1 for hot core and <1 for its low-mass analog. We employ a radiative transfer model to investigate the transitions of some of the P-bearing species in diffuse cloud and hot core regions and estimate the line profiles. Our study estimates the required integration time to observe these transitions with ground-based and space-based telescopes. We also carry out quantum chemical computation of the infrared features of PH3, along with various impurities. We notice that SO2 overlaps with the PH3 bending-scissoring modes around similar to 1000-1100 cm(-1). We also find that the presence of CO2 can strongly influence the intensity of the stretching modes around similar to 2400 cm(-1) of PH3.

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  • Discovery of Two Infrared Objects with Strong Ice Absorption in the Akari Slitless Spectroscopic Survey of the Galactic Plane Reviewed

    Takashi Onaka, Tomoyuki Kimura, Itsuki Sakon, Takashi Shimonishi

    The Astrophysical Journal   916 ( 2 )   75 - 75   2021.8

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    DOI: 10.3847/1538-4357/ac0531

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  • Formation of chiral CO polyhedral crystals on icy interstellar grains Reviewed

    Akira Kouchi, Masashi Tsuge, Tetsuya Hama, Hiromasa Niinomi, Naoki Nakatani, Takashi Shimonishi, Yasuhiro Oba, Yuki Kimura, Sin-iti Sirono, Satoshi Okuzumi, Munetake Momose, Kenji Furuya, Naoki Watanabe

    Monthly Notices of the Royal Astronomical Society   505 ( 1 )   1530 - 1542   2021.6

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    <title>ABSTRACT</title>
    The crystallinity and morphology of solid carbon monoxide (CO) on icy interstellar grains were examined by observing the deposition, crystallization, and UV and electrons irradiation of solid CO using transmission electron microscopy. Herein, we found that solid CO deposited in molecular clouds was crystalline, and that even if amorphous CO was deposited, amorphous CO crystallized within 103 yr at 10 K. Conversely, crystalline CO was not amorphized by UV rays or electron beam at 10 K. These results indicated the occurrence of chiral crystalline CO instead of amorphous CO in space. Furthermore, the large surface diffusion coefficients of CO on eamorphous H2O and crystalline CO at 10 K facilitated the morphological equilibration of crystalline CO. Bad wetting of crystalline CO with amorphous H2O proved that the morphology of the ice grains was not spherical with an onion-like structure, as hitherto assumed, but rather it was a polyhedral crystalline CO attached to amorphous H2O. This has important implications for phenomena associated with the collision and subsequent sticking between ice grains, surface chemical reactions, non-thermal desorption of molecules and the origin of homochirality in interstellar biomolecules.

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  • Identification of Methyl Isocyanate and Other Complex Organic Molecules in a Hot Molecular Core, G31.41+0.31 Reviewed

    Prasanta Gorai, Ankan Das, Takashi Shimonishi, Dipen Sahu, Suman Kumar Mondal, Bratati Bhat, Sandip K. Chakrabarti

    The Astrophysical Journal   907 ( 108 )   1 - 22   2021

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  • An Experimental Study of Chemical Desorption for Phosphine in Interstellar Ice Reviewed

    Thanh Nguyen, Yasuhiro Oba, Takashi Shimonishi, Akira Kouchi, Naoki Watanabe

    The Astrophysical Journal   898 ( 2 )   L52 - L52   2020.8

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    Phosphine (PH3), an important molecule for the chemistry of phosphorus (P)-bearing species in the interstellar medium (ISM) is considered to form primarily on interstellar grains. However, no report exists on the processes of PH(3)formation on grains. Here, we experimentally studied the reactions of hydrogen (H) atoms and PH(3)molecules on compact amorphous solid water, with a particular focus on the chemical desorption of PH(3)at 10-30 K. After exposure to H atoms for 120 minutes, up to 50% of solid PH(3)was lost from the icy surface. On the basis of experiments using deuterium atoms, it was concluded that the loss of PH(3)resulted from chemical desorption through the reactions PH3+ H -> PH2 + H(2)and/or PH2+ H -> PH3. The effective desorption cross-section was similar to 5 x 10(-17)cm(2), which is three times larger than that of hydrogen sulfide measured under similar experimental conditions. The present results suggest that the formation of PH3, and possibly PH(2)and PH, followed by their desorption from icy grains, may contribute to the formation of PN and PO in the gas phase, and thus may play a role in the P chemistry of the ISM.

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  • Systematic Study on the Absorption Features of Interstellar Ices in the Presence of Impurities Reviewed

    Prasanta Gorai, Milan Sil, Ankan Das, Bhalamurugan Sivaraman, Sandip K. Chakrabarti, Sergio Ioppolo, Cristina Puzzarini, Zuzana Kanuchova, Anita Dawes, Marco Mendolicchio, Giordano Mancini, Vicenzo Barone, Naoki Nakatani, Takashi Shimonishi, Nigel Mason

    ACS Earth and Space Chemistry   4 ( 6 )   920 - 946   2020.6

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    DOI: 10.1021/acsearthspacechem.0c00098

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  • Chemistry and Physics of a Low-metallicity Hot Core in the Large Magellanic Cloud Reviewed

    Takashi Shimonishi, Ankan Das, Nami Sakai, Kei E. I. Tanaka, Yuri Aikawa, Takashi Onaka, Yoshimasa Watanabe, Yuri Nishimura

    The Astrophysical Journal   891 ( 2 )   164 - 164   2020.3

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    DOI: 10.3847/1538-4357/ab6e6b

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  • Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds Reviewed

    Marta Sewiło, Steven B. Charnley, Peter Schilke, Vianney Taquet, Joana M. Oliveira, Takashi Shimonishi, Eva Wirström, Remy Indebetouw, Jacob L. Ward, Jacco Th. van Loon, Jennifer Wiseman, Sarolta Zahorecz, Toshikazu Onishi, Akiko Kawamura, C.-H. Rosie Chen, Yasuo Fukui, Roya Hamedani Golshan

    ACS Earth and Space Chemistry   3 ( 10 )   2088 - 2109   2019.10

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    DOI: 10.1021/acsearthspacechem.9b00065

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  • Molecular-cloud-scale Chemical Composition. III. Constraints of Average Physical Properties through Chemical Models Reviewed

    Harada Nanase, Nishimura Yuri, Watanabe Yoshimasa, Yamamoto Satoshi, Aikawa Yuri, Sakai Nami, Shimonishi Takashi

    The Astrophysical Journal   871 ( 2 )   1 - 24   2019.2

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  • A Multiline Study of a High-mass Young Stellar Object in the Small Magellanic Cloud with ALMA: The Detection of Methanol Gas at 0.2 Solar Metallicity Reviewed

    Takashi Shimonishi, Yoshimasa Watanabe, Yuri Nishimura, Yuri Aikawa, Satoshi Yamamoto, Takashi Onaka, Nami Sakai, Akiko Kawamura

    The Astrophysical Journal   862 ( 102 )   1 - 14   2018.7

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  • Adsorption Energies of Carbon, Nitrogen, and Oxygen Atoms on the Low-temperature Amorphous Water Ice: A Systematic Estimation from Quantum Chemistry Calculations Reviewed

    Takashi Shimonishi, Naoki Nakatani, Kenji Furuya, Tetsuya Hama

    Astrophysical Journal   855 ( 1 )   1 - 11   2018.3

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    We propose a new simple computational model to estimate the adsorption energies of atoms and molecules to low-temperature amorphous water ice, and we present the adsorption energies of carbon (3 P), nitrogen (4 S), and oxygen (3 P) atoms based on quantum chemistry calculations. The adsorption energies were estimated to be 14,100 ±420 K for carbon, 400 ±30 K for nitrogen, and 1440 ±160 K for oxygen. The adsorption energy of oxygen is consistent with experimentally reported values. We found that the binding of a nitrogen atom is purely physisorption, while that of a carbon atom is chemisorption, in which a chemical bond to an O atom of a water molecule is formed. That of an oxygen atom has a dual character, with both physisorption and chemisorption. The chemisorption of atomic carbon also implies the possibility of further chemical reactions to produce molecules bearing a C-O bond, though this may hinder the formation of methane on water ice via sequential hydrogenation of carbon atoms. These properties would have a large impact on the chemical evolution of carbon species in interstellar environments. We also investigated the effects of newly calculated adsorption energies on the chemical compositions of cold dense molecular clouds with the aid of gas-ice astrochemical simulations. We found that abundances of major nitrogen-bearing molecules, such as N2 and NH3, are significantly altered by applying the calculated adsorption energy, because nitrogen atoms can thermally diffuse on surfaces, even at 10 K.

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  • Molecular-cloud-scale Chemical Composition. II. Mapping Spectral Line Survey toward W3(OH) in the 3mm Band Reviewed

    Yuri Nishimura, Yoshimasa Watanabe, Nanase Harada, Takashi Shimonishi, Nami Sakai, Yuri Aikawa, Akiko Kawamura, Satoshi Yamamoto

    ASTROPHYSICAL JOURNAL   848 ( 1 )   1 - 17   2017.10

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    To study a molecular-cloud-scale chemical composition, we conducted a mapping spectral line survey toward the Galactic molecular cloud W3(OH), which is one of the most active star-forming regions in the Perseus arm. We conducted our survey through the use of the Nobeyama Radio Observatory 45 m telescope, and observed the area of 16' x 16', which corresponds to 9.0 pc x 9.0 pc. The observed frequency ranges are 87-91, 96-103, and 108-112 GHz. We prepared the spectrum averaged over the observed area, in which eight molecular species (CCH, HCN, HCO+, HNC, CS, SO, (CO)-O-18, and (CO)-C-13) are identified. On the other hand, the spectrum of the W3(OH) hot core observed at a 0.17 pc resolution shows the lines of various molecules such as OCS, H2CS CH3CCH, and CH3CN in addition to the above species. In the spatially averaged spectrum, emission of the species concentrated just around the star-forming core, such as CH3OH and HC3N, is fainter than in the hot core spectrum, whereas emission of the species widely extended over the cloud such as CCH is relatively brighter. We classified the observed area into five subregions according to the integrated intensity of (CO)-C-13, and evaluated the contribution to the averaged spectrum from each subregion. The CCH, HCN, HCO+, and CS lines can be seen even in the spectrum of the subregion with the lowest (CO)-C-13 integrated intensity range (&lt; 10 K km s(-1)). Thus, the contributions of the spatially extended emission is confirmed to be dominant in the spatially averaged spectrum.

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  • Molecular-cloud-scale Chemical Composition. I. A Mapping Spectral Line Survey toward W51 in the 3mm Band Reviewed

    Yoshimasa Watanabe, Yuri Nishimura, Nanase Harada, Nami Sakai, Takashi Shimonishi, Yuri Aikawa, Akiko Kawamura, Satoshi Yamamoto

    ASTROPHYSICAL JOURNAL   845 ( 2 )   1 - 29   2017.8

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    We have conducted a mapping spectral line survey toward the Galactic giant molecular cloud W51 in the 3mm band with the Mopra 22m telescope in order to study an averaged chemical composition of the gas extended over a molecular-cloud scale in our Galaxy. We have observed the area of 25'x30', which corresponds to 39 pcx47 pc. The frequency ranges of the observation are 85.1-101.1 GHz and 107.0-114.9 GHz. In the spectrum spatially averaged over the observed area, spectral lines of 12 molecular species and 4 additional isotopologues are identified. An intensity pattern of the spatially averaged spectrum is found to be similar to that of the spiral arm in the external galaxy M51, indicating that these two sources have similar chemical compositions. The observed area has been classified into five subregions according to the integrated intensity of (CO)-C-13( J =1-0) ( I-13CO), and contributions of the fluxes of 11 molecular lines from each subregion to the averaged spectrum have been evaluated. For most of the molecular species, 50% or more of the flux comes from the subregions with I13CO from 25 to 100Kkms(-1), which does not involve active star-forming regions. Therefore, the molecular-cloudscale spectrum observed in the 3mm band hardly represents the chemical composition of star-forming cores, but mainly represents the chemical composition of an extended quiescent molecular gas. The present result constitutes a sound base for interpreting the spectra of external galaxies at a resolution of a molecular-cloud scale (similar to 10pc) or larger.

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  • Ice Absorption Features in NIR Spectra of Galactic Objects Reviewed

    Mori Tamami I, Onaka Takashi, Sakon Itsuki, Ohsawa Ryou, Kaneda Hidehiro, Yamagishi Mitsuyoshi, Okada Yoko, Tanaka Masahiro, Shimonishi, Takashi

    Publications of The Korean Astronomical Society   32 ( 1 )   105 - 107   2017.3

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    DOI: 10.5303/PKAS.2017.32.1.105

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  • Processing of Interstellar Medium as Divulged by Akari Reviewed

    Onaka Takashi, Mori Tamami I, Ohsawa Ryou, Sakon Itsuki, Bell Aaron C, Hammonds Mark, Shimonishi Takashi, Ishihara Daisuke, Kaneda Hidehiro, Okada Yoko, Tanaka Masahiro

    Publications of The Korean Astronomical Society   32 ( 1 )   77 - 81   2017.3

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    DOI: 10.5303/PKAS.2017.32.1.077

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  • AKARI Infrared Camera Survey of the Large Magellanic Cloud Reviewed

    Shimonishi Takashi, Kato Daisuke, Ita Yoshifusa, Onaka Takashi, AKARI/IRC LMC Team

    Publications of The Korean Astronomical Society   32 ( 1 )   83 - 85   2017.3

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    DOI: 10.5303/PKAS.2017.32.1.083

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  • Study of CO2/H2O Ice Abundance Ratios in Nearby Galaxies with the Akari Near-Infrared Spectroscopy Reviewed

    Yamagishi Mitsuyoshi, Kaneda Hidehiro, Oyabu Shinki, Ishihara Daisuke, Onaka Takashi, Shimonishi Takashi, Suzuki Toyoaki

    Publications of The Korean Astronomical Society   32 ( 1 )   141 - 145   2017.3

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    DOI: 10.5303/PKAS.2017.32.1.141

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  • SPECTRAL LINE SURVEY TOWARD A MOLECULAR CLOUD IN IC10 Reviewed

    Yuri Nishimura, Takashi Shimonishi, Yoshimasa Watanabe, Nami Sakai, Yuri Aikawa, Akiko Kawamura, Satoshi Yamamoto

    ASTROPHYSICAL JOURNAL   829 ( 2 )   1 - 8   2016.10

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    We have conducted a spectral line survey observation in the 3 mm band toward the low-metallicity dwarf galaxy IC10 with the 45 m radio telescope of the Nobeyama Radio Observatory to explore its chemical composition at a molecular-cloud scale (similar to 80 pc). The CS, SO, CCH, HCN, HCO+, and HNC lines are detected for the first time in this galaxy in addition to the CO and (CO)-C-13 lines, while the c-C3H2, CH3OH, CN, (CO)-O-18, and N2H+ lines are not detected. The spectral intensity pattern is found to be similar to those observed toward molecular clouds in the Large Magellanic Cloud (LMC), whose metallicity is as low as IC10. Nitrogen-bearing species are deficient in comparison with the Galactic molecular clouds due to a lower elemental abundance of nitrogen. CCH is abundant in comparison with Galactic translucent clouds, whereas CH3OH may be deficient. These characteristic trends for CCH and CH3OH are also seen in the LMC, and seem to originate from photodissociation regions more extended in the peripheries of molecular clouds due to the lower metallicity condition.

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  • THE DETECTION OF A HOT MOLECULAR CORE IN THE LARGE MAGELLANIC CLOUD WITH ALMA Reviewed

    Takashi Shimonishi, Takashi Onaka, Akiko Kawamura, Yuri Aikawa

    ASTROPHYSICAL JOURNAL   827 ( 1 )   1 - 20   2016.8

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    We report the first detection of a hot molecular core outside our Galaxy based on radio observations with ALMA toward a high-mass young stellar object (YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC). Molecular emission lines of CO, (CO)-O-17, HCO+, (HCO+)-C-13, H2CO, NO, SiO, H2CS, (SO)-S-33, (SO2)-S-32, (SO2)-S-34, and (SO2)-S-33 are detected from a compact region (similar to 0.1 pc) associated with a high-mass YSO, ST11. The temperature of molecular gas is estimated to be higher than 100 K based on rotation diagram analysis of SO2 and (SO2)-S-34 lines. The compact source size, warm gas temperature, high density, and rich molecular lines around a high-mass protostar suggest that ST11 is associated with a hot molecular core. We find that the molecular abundances of the LMC hot core are significantly different from those of Galactic hot cores. The abundances of CH3OH, H2CO, and HNCO are remarkably lower compared to Galactic hot cores by at least 1-3 orders of magnitude. We suggest that these abundances are characterized by the deficiency of molecules whose formation requires the hydrogenation of CO on grain surfaces. In contrast, NO shows a high abundance in ST11 despite the notably low abundance of nitrogen in the LMC. A multitude of SO2 and its isotopologue line detections in ST11 imply that SO2 can be a key molecular tracer of hot core chemistry in metal-poor environments. Furthermore, we find molecular outflows around the hot core, which is the second detection of an extragalactic protostellar outflow. In this paper, we discuss the physical and chemical characteristics of a hot molecular core in the low metallicity environment.

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  • SPECTRAL LINE SURVEY TOWARD MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD Reviewed

    Yuri Nishimura, Takashi Shimonishi, Yoshimasa Watanabe, Nami Sakai, Yuri Aikawa, Akiko Kawamura, Satoshi Yamamoto

    ASTROPHYSICAL JOURNAL   818 ( 2 )   1 - 17   2016.2

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    Spectral line survey observations of seven. molecular clouds in the Large Magellanic Cloud (LMC) have been conducted in the 3 mm band with the Mopra 22 m telescope to reveal chemical compositions in low metallicity conditions. Spectral lines of fundamental species such as CS, SO, CCH, HCN, HCO+, and HNC are detected in addition to those of CO and (CO)-C-13, while CH3OH is not detected in any source and N2H+ is marginally detected in two sources. The molecular-cloud scale (10 pc scale) chemical composition is found to be similar among the seven. sources regardless of different star formation activities, and hence, it represents the chemical composition characteristic of. the LMC without influences by. star formation activities. In comparison with chemical compositions of Galactic sources, the characteristic features are (1) deficient N-bearing molecules, (2) abundant CCH, and (3) deficient CH3OH. Feature (1) is due to a lower elemental abundance of nitrogen in the LMC, whereas. features (2) and (3) seem to originate from extended photodissociation regions and warmer temperature in cloud peripheries due to a lower abundance of dust grains in the low metallicity condition. In spite of general resemblance of chemical abundances among the seven sources, the CS/HCO+ and SO/HCO+ ratios are found to be slightly higher in a quiescent molecular cloud. An origin of this trend is discussed in relation to possible depletion of sulfur along the molecular cloud formation.

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  • CONCURRENT FORMATION OF CARBON AND SILICATE DUST IN NOVA V1280 SCO Reviewed

    Itsuki Sakon, Shigeyuki Sako, Takashi Onaka, Takaya Nozawa, Yuki Kimura, Takuya Fujiyoshi, Takashi Shimonishi, Fumihiko Usui, Hidenori Takahashi, Ryou Ohsawa, Akira Arai, Makoto Uemura, Takahiro Nagayama, Bon-Chul Koo, Takashi Kozasa

    ASTROPHYSICAL JOURNAL   817 ( 2 )   1 - 23   2016.2

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    We present infrared multi-epoch observations of the dust-forming nova V1280 Sco over similar to 2000 days from the outburst. The temporal evolution of the infrared spectral energy distributions at 1272, 1616, and 1947 days can be explained by the emissions produced by amorphous carbon dust of mass (6.6-8.7) x 10(-8) M-circle dot with a representative grain size of 0.01. mu m and astronomical silicate dust of mass (3.4-4.3) x 10(-7) M-circle dot with a representative grain size of 0.3-0.5 mu m. Both of these dust species travel farther away from the white dwarf without apparent mass evolution throughout those later epochs. The dust formation scenario around V1280 Sco suggested from our analyses is that the amorphous carbon dust is formed in the nova ejecta followed by the formation of silicate dust either in the expanding nova ejecta or as a result of the interaction between the nova wind and the circumstellar medium.

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  • VLT/ISAAC infrared spectroscopy of embedded high-mass YSOs in the Large Magellanic Cloud: Methanol and the 3.47 mu m band Reviewed

    T. Shimonishi, E. Dartois, T. Onaka, F. Boulanger

    ASTRONOMY & ASTROPHYSICS   585 ( A107 )   1 - 20   2016.1

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    Aims. This study aims to elucidate a possible link between chemical properties of ices in star-forming regions and environmental characteristics (particularly metallicity) of the host galaxy. The Large Magellanic Cloud (LMC) is an excellent target to study properties of interstellar and circumstellar medium in a different galactic environment thanks to its proximity and low metallicity.
    Methods. We performed near-infrared, L-band spectroscopic observations toward embedded high-mass young stellar objects (YSOs) in the LMC with the Infrared Spectrometer And Array Camera (ISAAC) at the Very Large Telescope. The 3.2-3.7 mu m spectral region, which is accessible from ground-based telescopes, is important for ice studies, since various C-H stretching vibrations of carbon bearing species fall in this region.
    Results. We obtained medium-resolution (R similar to 500) spectra in the 3-4 mu m range for nine high-mass YSOs in the LMC. Additionally, we analyzed archival ISAAC data of two LMC YSOs. We detected absorption bands due to solid H2O and CH3OH as well as the 3.47 mu m absorption band. The properties of these bands are investigated based on comparisons with Galactic embedded sources. The 3.53 mu m CH3OH ice absorption band for the LMC YSOs is found to be absent or very weak compared to that seen toward Galactic sources. The absorption band is weakly detected for two out of eleven objects. We estimate the abundance of the CH3OH ice, which suggests that solid CH3OH is less abundant for high-mass YSOs in the LMC than those in our Galaxy. The 3.47 mu m absorption band is detected toward six out of eleven LMC YSOs. We found that the 3.47 mu m band and the H2O ice band correlate similarly between the LMC and Galactic samples, but the LMC sources seem to require a slightly higher H2O ice threshold for the appearance of the 3.47 mu m band. For the LMC sources with relatively large H2O ice optical depths, we found that the strength ratio of the 3.47 mu m band relative to the water ice band is only marginally lower than those of the Galactic sources.
    Conclusions. We propose that grain surface reactions at a relatively high dust temperature (warm ice chemistry) are responsible for the observed characteristics of ice chemical compositions in the LMC; i.e., the low abundance of solid CH3OH presented in this work as well as the high abundance of solid CO2 reported in previous studies. We suggest that this warm ice chemistry is one of the important characteristics of interstellar and circumstellar chemistry in low metallicity environments. The low abundance of CH3OH in the solid phase implies that formation of complex organic molecules from methanol-derived species is less efficient in the LMC. For the 3.47 mu m band, the observed difference in the water ice threshold may suggest that a more shielded environment is necessary for the formation of the 3.47 mu m band carrier in the LMC. On the one hand, in well-shielded regions of the LMC, our results suggest that the lower metallicity and different interstellar environment of the LMC have little effect on the abundance ratio of the 3.47 mu m band carrier and water ice.

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  • Carbon and silicate dust formation in V1280 Sco Reviewed

    I. Sakon, S. Sako, T. Oanaka, T. Nozawa, Y. Kimura, T. Fujiyoshi, T. Shimonishi, F. Usui, H. Takahashi, R. Ohsawa, A. Arai, M. Uemura, T. Nagayama, B-C Koo, T. Kozasa

    11TH PACIFIC RIM CONFERENCE ON STELLAR ASTROPHYSICS: PHYSICS AND CHEMISTRY OF THE LATE STAGES OF STELLAR EVOLUTION, PTS 1-6   728   062006   2016

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    This study investigates the temporal evolution of the infrared emission from the dusty nova V1280 Sco over 2000 days from the outburst. We have revealed that the infrared spectral energy distributions at 1272, 1616 and 1947 days are explained by the emissions produced by amorphous carbon dust of mass (6.6-8.7) x10(-8) M circle dot with a representative grain size of 0.01 mu m and astronomical silicate dust of mass (3.4-4.3) x10(-7) M circle dot with a representative grain size of 0.3-0.5 mu m. Both of carbon and silicate dust travel farther away from the white dwarf without an apparent mass evolution throughout those later epochs.

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  • SYSTEMATIC VARIATIONS IN CO2/H2O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES FOUND WITH AKARI NEAR-INFRARED SPECTROSCOPY Reviewed

    M. Yamagishi, H. Kaneda, D. Ishihara, S. Oyabu, T. Onaka, T. Shimonishi, T. Suzuki

    ASTROPHYSICAL JOURNAL   807 ( 1 )   1 - 7   2015.7

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    We report CO2/H2O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5-5.0 mu m) spectra. The CO2/H2O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 +/- 0.01. The previous study on M82 revealed that the CO2/H2O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Bra line to the polycyclic aromatic hydrocarbon (PAH) 3.3 mu m feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO2/H2O ice abundance and Bra/PAH 3.3 mu m intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO2/H2O ice abundance ratios in a galaxy in addition to the Bra/PAH 3.3 mu m ratios. We find that the CO2/H2O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO2/H2O ice abundance ratios tend to be high in young star-forming galaxies.

    DOI: 10.1088/0004-637X/807/1/29

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  • AKARI NIR spectroscopy of interstellar ices

    Takashi Onaka, Tamami I. Mori, Itsuki Sakon, Fumihiko Usui, Ronin Wu, Takashi Shimonishi

    Proceedings of the International Astronomical Union   11 ( 1 )   319 - 320   2015

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    The Infrared Camera (IRC) onboard AKARI has a near-infrared (2-5μm) spectroscopic capability with high sensitivity that allows us to study the major ice components in various objects. In particular, H2O and CO2 ice absorption features have been detected towards nearby galaxies, including several young stellar objects (YSOs) in the Large Magellanic Cloud (LMC), as well as a number of HII region-PDR complexes for the first time by IRC spectroscopy. While observations in the LMC show a high ratio (~0.34) of the CO2 to H2O ice column densities, the ratios in Galactic HII-region-PDR complexes are in the range of 0.1-0.2, being compatible with those found in Galactic massive YSOs in previous studies. The good correlation supports concurrent formation of the two ice species on the grain surface and the higher ratio in the low-metallicity LMC suggests possible environmental effects in the formation process.

    DOI: 10.1017/S1743921316003161

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  • Spectral Line Survey Toward Quiescent Giant Molecular Clouds in the Large Magellanic Cloud Reviewed

    Yuri Nishimura, Takashi Shimonishi, Yoshimasa Watanabe, Nami Sakai, Yuri Aikawa, Akiko Kawamura, Satoshi Yamamoto

    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR   499   165 - 166   2015

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    Spectral line survey observations in the 3 mm band have been conducted toward 7 molecular clouds in the Large Magellanic Cloud (LMC) with the Mopra 22 m telescope. Spectral lines of the fundamental species CCH, HCN, HCO+, HNC, CS, SO, and c-C3H2 are detected. Although the 7 sources are different in star-formation activities, chemical compositions averaged over the 10 pc beam are similar to one another. We find that N-bearing species are deficient and CCH is relatively abundant in comparison with metal-rich environments. In spite of overall similarity of the chemical compositions, we also find a trend that the CS/HCO+ and SO/HCO+ ratios are higher for starless clouds.

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  • OBSERVATIONAL STUDIES ON THE NEAR-INFRARED UNIDENTIFIED EMISSION BANDS IN GALACTIC H II REGIONS (vol 784, 53, 2014) Reviewed

    Tamami I. Mori, Takashi Onaka, Itsuki Sakon, Daisuke Ishihara, Takashi Shimonishi, Ryou Ohsawa, Aaron C. Bell

    ASTROPHYSICAL JOURNAL   792 ( 1 )   80   2014.9

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    DOI: 10.1088/0004-637X/792/1/80

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  • Near-Infrared Spectroscopy of Diffuse Galactic Radiation with AKARI/IRC Reviewed

    Takashi Onaka, Tamami Mori, Itsuki Sakon, Ryou Ohsawa, Tomohiko Nakamura, Ho-Gyu Lee, Ingrid M. Koch, Takashi Shimonishi, Hidehiro Kaneda, Yoko Okada, Masahiro Tanaka

    Proceedings of The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments — PoS(LCDU2013)   2014.6

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    DOI: 10.22323/1.207.0112

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  • Spitzer Space Telescope spectra of post-AGB stars in the Large Magellanic Cloud - polycyclic aromatic hydrocarbons at low metallicities Reviewed

    Mikako Matsuura, Jeronimo Bernard-Salas, T. Lloyd Evans, Kevin M. Volk, Bruce J. Hrivnak, G. C. Sloan, You-Hua Chu, Robert Gruendl, Kathleen E. Kraemer, Els Peeters, R. Szczerba, P. R. Wood, Albert A. Zijlstra, S. Hony, Yoshifusa Ita, Devika Kamath, Eric Lagadec, Quentin A. Parker, Warren A. Reid, Takashi Shimonishi, H. Van Winckel, Paul M. Woods, F. Kemper, Margaret Meixner, M. Otsuka, R. Sahai, B. A. Sargent, J. L. Hora, Iain McDonald

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   439 ( 2 )   1472 - 1493   2014.4

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    This paper reports variations of polycyclic aromatic hydrocarbons (PAHs) features that were found in Spitzer Space Telescope spectra of carbon-rich post-asymptotic giant branch (post-AGB) stars in the Large Magellanic Cloud (LMC). The paper consists of two parts. The first part describes our Spitzer spectral observing programme of 24 stars including post-AGB candidates. The latter half of this paper presents the analysis of PAH features in 20 carbon-rich post-AGB stars in the LMC, assembled from the Spitzer archive as well as from our own programme. We found that five post-AGB stars showed a broad feature with a peak at 7.7 mu m, that had not been classified before. Further, the 10-13 mu m PAH spectra were classified into four classes, one of which has three broad peaks at 11.3, 12.3 and 13.3 mu m rather than two distinct sharp peaks at 11.3 and 12.7 mu m, as commonly found in H ii regions. Our studies suggest that PAHs are gradually processed while the central stars evolve from post-AGB phase to planetary nebulae, changing their composition before PAHs are incorporated into the interstellar medium. Although some metallicity dependence of PAH spectra exists, the evolutionary state of an object is more significant than its metallicity in determining the spectral characteristics of PAHs for LMC and Galactic post-AGB stars.

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  • OBSERVATIONAL STUDIES ON THE NEAR-INFRARED UNIDENTIFIED EMISSION BANDS IN GALACTIC H II REGIONS Reviewed

    Tamami I. Mori, Takashi Onaka, Itsuki Sakon, Daisuke Ishihara, Takashi Shimonishi, Ryou Ohsawa, Aaron C. Bell

    ASTROPHYSICAL JOURNAL   784 ( 1 )   1 - 12   2014.3

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    Using a large collection of near-infrared spectra (2.5-5.4 mu m) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 mu m features, most spectra show a relatively weak emission feature at 5.22 mu m with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 mu m band (previously reported). By careful analysis, we find good correlations between the 5.25 mu m band and both the aromatic hydrocarbon feature at 3.3 mu m and the aliphatic hydrocarbon features at around 3.4-3.6 mu m. The present results give us convincing evidence that the astronomical 5.25 mu m band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I-3.4-3.6 mu m/ I-3.3 mu m decreases against the ratio of the 3.7 mu m continuum intensity to the 3.3 mu m band, I-cont, 3.7 mu m/ I-3.3 mu m, which is an indicator of the ionization fraction of PAHs. The midinfrared color of I-9 mu m/ I-18 mu m also declines steeply against the ratio of the hydrogen recombination line Bra at 4.05 mu m to the 3.3 mu m band, I-Br alpha / I-3.3 mu m. These facts indicate possible dust processing inside or at the boundary of ionized gas.

    DOI: 10.1088/0004-637X/784/1/53

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  • Difference in the spatial distribution between H2O and CO 2 ICES in M 82 found with AKARI Reviewed

    Mitsuyoshi Yamagishi, Hidehiro Kaneda, Daisuke Ishihara, Shinki Oyabu, Takashi Onaka, Takashi Shimonishi, Toyoaki Suzuki, Young Chol Minh

    Astrophysical Journal Letters   773 ( 2 )   1 - 5   2013.8

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    With AKARI, we obtain the spatially resolved near-infrared (NIR) (2.5-5.0 μm) spectra for the nearby starburst galaxy M 82. These spectra clearly show absorption features due to interstellar ices. Based on the spectra, we created the column density maps of H2O and CO2 ices. As a result, we find that the spatial distribution of H2O ice is significantly different from that of CO2 ice
    H2O ice is widely distributed, while CO2 ice is concentrated near the galactic center. Our result reveals for the first time variations in CO2/H 2O ice abundance ratio on a galactic scale, suggesting that an ice-forming interstellar environment changes within a galaxy. We discuss the cause of the spatial variations in the ice abundance ratio, utilizing spectral information on the hydrogen recombination Brα and Brβ lines and the polycyclic aromatic hydrocarbon 3.3 μm emission appearing in the AKARI NIR spectra. © 2013. The American Astronomical Society. All rights reserved.

    DOI: 10.1088/2041-8205/773/2/L37

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  • Akari infrared camera survey of the large magellanic cloud. II. the near-infrared spectroscopic catalog Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    Astronomical Journal   145 ( 2 )   1 - 14   2013.2

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    We performed a near-infrared spectroscopic survey toward an area of 10 deg2 of the Large Magellanic Cloud (LMC) with the infrared satellite AKARI. Observations were carried out as part of the AKARI Large-area Survey of the Large Magellanic Cloud (LSLMC). The slitless multi-object spectroscopic capability of the AKARI/IRC enabled us to obtain low-resolution (R 20) spectra in 2-5 μm for a large number of point sources in the LMC. As a result of the survey, we extracted about 2000 infrared spectra of point sources. The data are organized as a near-infrared spectroscopic catalog. The catalog includes various infrared objects such as young stellar objects (YSOs), asymptotic giant branch (AGB) stars, supergiants, and so on. It is shown that 97% of the catalog sources have corresponding photometric data in the wavelength range from 1.2 to 11 μm, and 67% of the sources also have photometric data up to 24 μm. The catalog allows us to investigate near-infrared spectral features of sources by comparison with their infrared spectral energy distributions. In addition, it is estimated that about 10% of the catalog sources are observed at more than two different epochs. This enables us to study a spectroscopic variability of sources by using the present catalog. Initial results of source classifications for the LSLMC samples are presented. We classified 659 LSLMC spectra based on their near-infrared spectral features by visual inspection. As a result, it is shown that the present catalog includes 7 YSOs, 160 C-rich AGBs, 8 C-rich AGB candidates, 85 O-rich AGBs, 122 blue and yellow supergiants, 150 red super giants, and 128 unclassified sources. Distributions of the classified sources on the color-color and color-magnitude diagrams are discussed in the text. Continuous wavelength coverage and high spectroscopic sensitivity in 2-5 μm can only be achieved by space observations. This is an unprecedented large-scale spectroscopic survey toward the LMC in the near-infrared. A large number of near-infrared spectral data provided by the survey possess scientific potential that can be applied to various studies. In this paper, we present the details of the spectroscopic survey and the catalog, and discuss its scientific applications. © 2013. The American Astronomical Society. All rights reserved..

    DOI: 10.1088/0004-6256/145/2/32

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  • Infrared Spectroscopy of YSOs in the Magellanic Clouds Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    NEW TRENDS IN RADIO ASTRONOMY IN THE ALMA ERA: THE 30TH ANNIVERSARY OF NOBEYAMA RADIO OBSERVATORY   476   307 - 308   2013

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    For the last few years, it has been pioneer days for infrared spectroscopic studies of extragalactic young stellar objects (YSOs). A number of embedded YSOs are spectroscopically identified in the Magellanic Clouds with AKARI and Spitzer, and their near- to mid-infrared spectral features are investigated in detail. In this proceeding, we are going to present our current research on the infrared spectroscopic observations of ices and dust around embedded YSOs in the Magellanic Clouds with AKARI.

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  • AKARI INFRARED CAMERA SURVEY OF THE LARGE MAGELLANIC CLOUD. I. POINT-SOURCE CATALOG Reviewed

    Daisuke Kato, Yoshifusa Ita, Takashi Onaka, Toshihiko Tanabe, Takashi Shimonishi, Itsuki Sakon, Hidehiro Kaneda, Akiko Kawamura, Takehiko Wada, Fumihiko Usui, Bon-Chul Koo, Mikako Matsuura, Hidenori Takahashi

    ASTRONOMICAL JOURNAL   144 ( 6 )   1 - 18   2012.12

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    We present a near-to mid-infrared point-source catalog of five photometric bands at 3.2, 7, 11, 15, and 24 mu m for a 10 deg(2) area of the Large Magellanic Cloud (LMC) obtained with the Infrared Camera on board the AKARI satellite. To cover the survey area the observations were carried out at three separate seasons from 2006 May to June, 2006 October to December, and 2007 March to July. The 10 sigma limiting magnitudes of the present survey are 17.9, 13.8, 12.4, 9.9, and 8.6 mag at 3.2, 7, 11, 15, and 24 mu m, respectively. The photometric accuracy is estimated to be about 0.1 mag at 3.2 mu m and 0.06-0.07 mag in the other bands. The position accuracy is 0 ''.3 at 3.2, 7, and 11 mu m and 1 ''.0 at 15 and 24 mu m. The sensitivities at 3.2, 7, and 24 mu m are roughly comparable to those of the Spitzer SAGE LMC point-source catalog, while the AKARI catalog provides the data at 11 and 15 mu m, covering the mid-infrared spectral range contiguously. Two types of catalog are provided: a Catalog and an Archive. The Archive contains all the detected sources, while the Catalog only includes the sources that have a counterpart in the Spitzer SAGE point-source catalog. The Archive contains about 650,000, 140,000, 97,000, 43,000, and 52,000 sources at 3.2, 7, 11, 15, and 24 mu m, respectively. Based on the catalog, we discuss the luminosity functions at each band, the color-color diagram, and the color-magnitude diagram using the 3.2, 7, and 11 mu m band data. Stars without circumstellar envelopes, dusty C-rich and O-rich stars, young stellar objects, and background galaxies are located at distinct regions in the diagrams, suggesting that the present catalog is useful for the classification of objects toward the LMC.

    DOI: 10.1088/0004-6256/144/6/179

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  • AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO2 IN 18 COMETS Reviewed

    Takafumi Ootsubo, Hideyo Kawakita, Saki Hamada, Hitomi Kobayashi, Mitsuru Yamaguchi, Fumihiko Usui, Takao Nakagawa, Munetaka Ueno, Masateru Ishiguro, Tomohiko Sekiguchi, Jun-ichi Watanabe, Itsuki Sakon, Takashi Shimonishi, Takashi Onaka

    ASTROPHYSICAL JOURNAL   752 ( 1 )   1 - 12   2012.6

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    We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 mu m. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H2O) at 2.7 mu m and carbon dioxide (CO2) at 4.3 mu m. The fundamental vibrational band of carbon monoxide (CO) around 4.7 mu m and the broad emission feature, probably related to carbon-hydrogen-bearing molecules, can also be recognized around the 3.3-3.5-mu m region in some of the comets. With respect to H2O, gas production rate ratios of CO2 have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO2/H2O production rate ratios in comets obtained so far. The CO2/H2O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within similar to 2.5 AU, since H2O ice fully sublimates there. The CO2/H2O ratio in cometary ice spans from several to similar to 30% among the comets observed at &lt;2.5 AU (13 out of the 17 comets). Alternatively, the ratio of CO/CO2 in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.

    DOI: 10.1088/0004-637X/752/1/15

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  • Summary of Observations of the Infrared Camera (IRC) onboard AKARI Reviewed

    T. Onaka, H. Matsuhara, T. Wada, D. Ishihara, Y. Ohyama, I. Sakon, T. Shimonishi, R. Ohsawa, T. I. Mori, F. Egusa, F. Usui, S. Takita, H. Murakami, S. Oyabu, M. Yamagishi, T. Mori, A. Mouri, T. Kondo, S. Suzuki, H. Kaneda, Y. Ita, T. Ootsubo

    SPACE TELESCOPES AND INSTRUMENTATION 2012: OPTICAL, INFRARED, AND MILLIMETER WAVE   8442   2012

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    AKARI, the Japanese satellite mission dedicated to infrared astronomy was launched in 2006 February and exhausted its liquid helium in 2007 August. During the cold mission phase, the Infrared Camera (IRC) onboard carried out an all-sky survey at 9 and 18 mu m with better spatial resolution and higher sensitivity than IRAS. Both bands also have slightly shorter wavelength coverage than IRAS 12 and 25 mu m bands and thus provide different information on the infrared sky. All-sky image data of the IRC are now in the final processing and will be released to the public within a year. After the exhaustion of the cryogen, the telescope and focal plane instruments of AKARI had still been kept at sufficiently low temperatures owing to the onboard cryocooler. Near-infrared (NIR) imaging and spectroscopic observations with the IRC had continued until 2011 May, when the spacecraft had a serious problem in the power supply system that forced us to terminate the observation. The IRC carried out nearly 20000 pointing observations in total despite of its near-earth orbit. About a half of them were performed after the exhaustion of the cryogen in the spectroscopic modes, which provided high-sensitivity NIR spectra from 2 to 5 mu m without disturbance of the terrestrial atmosphere. During the warm mission phase, the temperature of the instrument gradually increased and changed the array operation conditions. We present a summary of AKARI/IRC observations, including the all-sky mid-infrared diffuse data as well as the data taken in the warm mission phase.

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  • AKARI NEAR-INFRARED SPECTROSCOPIC OBSERVATIONS OF INTERSTELLAR ICES IN THE EDGE-ON STARBURST GALAXY NGC 253 Reviewed

    Mitsuyoshi Yamagishi, Hidehiro Kaneda, Daisuke Ishihara, Shinki Oyabu, Takashi Onaka, Takashi Shimonishi, Toyoaki Suzuki

    ASTROPHYSICAL JOURNAL LETTERS   731 ( 1 )   1 - 5   2011.4

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    We present the spatially resolved near-infrared (2.5-5.0 mu m) spectra of the edge-on starburst galaxy NGC 253 obtained with the Infrared Camera on board AKARI. Near the center of the galaxy, we clearly detect the absorption features of interstellar ices (H2O: 3.05 mu m, CO2: 4.27 mu m, and XCN: 4.62 mu m) and the emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 mu m and the hydrogen recombination line Br alpha at 4.05 mu m. We find that the distributions of the ices differ from those of the PAH and gas. We calculate the column densities of the ices and derive the abundance ratios of N(CO2)/N(H2O) = 0.17 +/- 0.05. They are similar to those obtained around the massive young stellar objects in our Galaxy (0.17 +/- 0.03), although a much stronger interstellar radiation field and higher dust temperature are expected near the center of NGC 253.

    DOI: 10.1088/2041-8205/731/1/L20

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  • AKARI NEAR-INFRARED SPECTROSCOPY OF 3 MICRON PAH AND 4 MICRON PAD FEATURES Reviewed

    T. Onaka, I. Sakon, R. Ohsawa, T. Shimonishi, Y. Okada, M. Tanaka, H. Kaneda

    PAHS AND THE UNIVERSE: A SYMPOSIUM TO CELEBRATE THE 25TH ANNIVERSARY OF THE PAH HYPOTHESIS   46   55 - +   2011

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    Near-infrared (NIR; 2.5-5 mu m) low-resolution (lambda/Delta lambda similar to 100) spectra were obtained for a number of Galactic and extragalactic objects with the Infrared Camera (IRC) in the AKARI warm mission. These data provide us with the first opportunity to make a systematic study of the 3.3-3.5 mu m PAH features in a galactic scale as well as within an object. Whereas the 3.3 mu m band is well resolved in most spectra, the 3.5 mu m band is not clearly separated from the 3.4 mu m band in the IRC spectrum. The intensity ratio of the summation of the 3.4 and 3.5 mu m bands to the 3.3 mu m band shows a tendency to increase towards the Galactic center, although a large variation in the ratio is also seen in a local scale. A search for deuterated PAH features in the 4 mu m region is carried out in IRC NIR spectra. Emission lines originating from the ionized gas together with the detector anomaly hamper an accurate search at certain wavelengths, but little convincing evidence has so far been obtained for the presence of significant features in 4.2-4.7 mu m. A conservative upper limit of a few percents is obtained for the integrated intensity ratio of the 4.4-4.7 mu m possible features to the 3.3-3.5 mu m PAH features in the spectra so far obtained.

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  • Spectroscopic observations of ices around embedded young stellar objects in the Large Magellanic Cloud with AKARI Reviewed

    T. Shimonishi, T. Onaka, D. Kato, I. Sakon, Y. Ita, A. Kawamura, H. Kaneda

    ASTRONOMY & ASTROPHYSICS   514 ( A12 )   1 - 12   2010.5

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    Aims. The aim of this study is to understand the chemical conditions of ices around embedded young stellar objects (YSOs) in the metal-poor Large Magellanic Cloud (LMC).
    Methods. We performed near-infrared (2.5-5 mu m) spectroscopic observations toward 12 massive embedded YSOs and their candidates in the LMC using the infrared camera (IRC) onboard AKARI. We estimated the column densities of the H2O, CO2, and CO ices based on their 3.05, 4.27, and 4.67 mu m absorption features, and we investigated the correlation between ice abundances and physical properties of YSOs.
    Results. The ice absorption features of H2O, CO2, (CO2)-C-13, CO, CH3OH, and possibly XCN are detected in the spectra. In addition, hydrogen recombination lines and PAH emission bands are detected toward the majority of the targets. The derived typical CO2/H2O ice ratio of our samples (similar to 0.36 +/- 0.09) is greater than that of Galactic massive YSOs (similar to 0.17 +/- 0.03), while the CO/H2O ice ratio is comparable. It is shown that the CO2 ice abundance does not correlate with the observed characteristics of YSOs: the strength of hydrogen recombination line and the total luminosity. Likewise, clear correlation is not seen between the CO ice abundance and YSO characteristics, but it is suggested that the CO ice abundance of luminous samples is significantly lower than in other samples.
    Conclusions. The systematic difference in the CO2 ice abundance around the LMC's massive YSOs, which was suggested by previous studies, is confirmed with the new near-IR data. We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC are responsible for the observed high abundance of the CO2 ice. It is suggested that the internal stellar radiation does not play an important role in the evolution of the CO2 ice around a massive YSO, while more volatile molecules like CO are susceptible to the effect of the stellar radiation.

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  • AKARI warm mission Reviewed

    Takashi Onaka, Hideo Matsuhara, Takehiko Wada, Daisuke Ishihara, Yoshifusa Ita, Youichi Ohyama, Takafumi Ootsubo, Shinki Oyabu, Itsuki Sakon, Takashi Shimonishi, Satoshi Takita, Tanabe Toshihiko, Fumihiko Usui, Hiroshi Murakami

    SPACE TELESCOPES AND INSTRUMENTATION 2010: OPTICAL, INFRARED, AND MILLIMETER WAVE   7731   2010

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    AKARI, the Japanese satellite mission dedicated for infrared astronomy launched in 2006 February, exhausted its 180 litter liquid helium (LHe) in 2007 August. After the LHe exhaustion, the telescope and focal plane of AKARI have still been kept less than 50K by the onboard cryocooler and near-infrared (NIR) observations with the Infrared Camera (IRC) are continuing. The data reduction software optimized for the warm mission enables us to carry out efficient and sensitive observations in the NIR despite the increase of hot pixels. In particular, the NIR spectroscopic capability of the IRC provides a unique opportunity to obtain spectra in 2.5-5 mu m with a high sensitivity, which will not be able to be carried out with any other facilities until JWST. An overview of the AKARI warm mission is given together with the performance and some observational results taken during the warm mission.

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  • Near-infrared Spectroscopic Observation of Ices around Extragalactic Young Stellar Objects Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    EXOPLANETS AND DISKS: THEIR FORMATION AND DIVERSITY   1158   155 - +   2009

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    We report the result of the 2-5 mu m spectroscopy of massive young stellar objects (YSOs) in the Large Magellanic Cloud (LMC) using the infrared satellite AKARI. Absorption features of H2O, CO2 and CO ices are detected toward these extragalactic YSOs, and derived CO2/H2O ratio in the LMC showed a higher value than galactic YSOs. In this proceeding, we discuss the difference of a chemical conditions around extragalactic YSOs.

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  • Ices around Extragalactic Young Stellar Objects Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    AKARI, A LIGHT TO ILLUMINATE THE MISTY UNIVERSE   418   55 - +   2009

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    The infrared spectra of young stellar objects (YSOs) often show absorption features of ices. So far, almost all of the observations of ices around YSOs have been limited to Galactic objects. We here report the result of 2.5-5 mu m spectroscopy of YSOs in the Large Magellanic Cloud with infrared satellite AKARI. Absorption features of H2O, CO2 and CO ices are detected toward these extragalactic YSOs, and derived CO2/H2O ice ratio in the LMC shows a higher value than Galactic YSOs. In this paper, we discuss the different chemical conditions around extragalactic YSOs.

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  • AKARI IRC Survey of the Large Magellanic Cloud: Outline of the Survey and Initial Results Reviewed

    Yoshifusa Ita, Takashi Onaka, Daisuke Kato, Toshihiko Tanabe, Itsuki Sakon, Hidehiro Kaneda, Akiko Kawamura, Takashi Shimonishi, Takehiko Wada, Fumihiko Usui, Bon-Chul Koo, Mikako Matsuura, Hidenori Takahashi, Yoshikazu Nakada, Tetsuo Hasegawa, Motohide Tamura

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   60   S435 - S451   2008.12

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    We observed an area of 10 deg(2) of the Large Magellanic Cloud using the Infrared Camera (IRC) on board AKARI. The observations were carried out using five imaging filters (3, 7, 11, 15, and 24 mu m) and a dispersion prism (2-5 mu m, lambda/Delta lambda similar to 20) equipped in the IRC. This paper describes an outline of our survey project, and presents some initial results using imaging data that detected over 5.9 x 10(5) near-infrared and 6.4 x 10(4) mid-infrared point sources. The 10 sigma detection limits of our survey are about 16.5, 14.0, 12.3, 10.8, and 9.2 in Vega-magnitude at 3, 7, 11, 15, and 24 mu m, respectively. The 11 and 15 Am data, which are unique to AKARI IRC, allow us to construct color-magnitude diagrams that are useful to identify stars with circumstellar dust. We found a new sequence in the color-magnitude diagram, which is attributed to red giants with luminosity fainter than that of the tip of the first red-giant branch. We suggest that this sequence is likely to be related to the broad emission feature of aluminum oxide at 11.5 mu m. The 11 and 15 mu m data also indicate that the ([11]-[15]) color of both oxygen-rich and carbon-rich red giants once becomes blue, and then turns red again in the course of their evolution, probably due to a change in the flux ratio of the silicate or silicon carbide emission feature at 10 or 11.3 mu m to the 15 mu m flux.

    DOI: 10.1093/pasj/60.sp2.S435

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  • AKARI Near-Infrared Spectroscopy: Detection of H2O and CO2 Ices toward Young Stellar Objects in the Large Magellanic Cloud Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    The Astrophysical Journal   686 ( 2 )   L99 - L102   2008.10

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

    We present the first results of AKARI Infrared Camera near-infrared spectroscopic survey of the Large Magellanic Cloud (LMC). We detected absorption features of the H2O ice 3.05 μm and the CO2 ice 4.27 μm stretching mode toward seven massive young stellar objects (YSOs). These samples are for the first time spectroscopically confirmed to be YSOs. We used a curve-of-growth method to evaluate the column densities of the ices and derived the CO2/H2O ratio to be 0.45 ± 0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17 ± 0.03). We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC may be responsible for the observed high CO2 ice abundance. © 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A.

    DOI: 10.1086/592948

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  • AKARI NEAR-INFRARED SPECTROSCOPY: DETECTION OF H2O AND CO2 ICES TOWARD YOUNG STELLAR OBJECTS IN THE LARGE MAGELLANIC CLOUD Reviewed

    Takashi Shimonishi, Takashi Onaka, Daisuke Kato, Itsuki Sakon, Yoshifusa Ita, Akiko Kawamura, Hidehiro Kaneda

    ASTROPHYSICAL JOURNAL LETTERS   686 ( 2 )   L99 - L102   2008.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    We present the first results of AKARI Infrared Camera near-infrared spectroscopic survey of the Large Magellanic Cloud (LMC). We detected absorption features of the H2O ice 3.05 mu m and the CO2 ice 4.27 mu m stretching mode toward seven massive young stellar objects (YSOs). These samples are for the first time spectroscopically confirmed to be YSOs. We used a curve-of-growth method to evaluate the column densities of the ices and derived the CO2/H2O ratio to be 0.45 +/- 0.17. This is clearly higher than that seen in Galactic massive YSOs (0.17 +/- 0.03). We suggest that the strong ultraviolet radiation field and/or the high dust temperature in the LMC may be responsible for the observed high CO2 ice abundance.

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MISC

  • 銀河系の果てに分子の森を観る Invited

    下西 隆

    天文月報 2022年4月号   2022.3

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  • 「あかり」と地上望遠鏡の連携が明らかにする低重元素量銀河中の原始星の化学 Invited

    下西隆

    ISASニュース   ( 470 )   1 - 3   2020.5

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  • Observations of Circumstellar Ices around Extragalactic Young Stellar Objects with SPICA

    Shimonishi Takashi, Onaka Takashi, Sakon Itsuki, Ita Yoshifusa, Kawamura Akiko, Kaneda Hidehiro

    ( 17 )   281 - 283   2018.3

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    Authorship:Lead author, Corresponding author   Language:English   Publisher:Japan Aerospace Exploration Agency (JAXA)  

    SPICA Science Conference from Exoplanets to Distant Galaxies: SPICA's New Window on the Cool Universe (June 18-21, 2013. Ito Hall, the University of Tokyo), Bunkyou-ku, Tokyo, JapanSpectroscopic observations with SPICA will provide us invaluable opportunities to study the chemical properties of circumstellar solids in various galactic environments beyond the Milky Way. In this proceedings, we discuss scientific importance and feasibility of spectroscopic observations of ices and dust around YSOs in nearby galaxies with SPICA.Physical characteristics: Original contains color illustrations

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  • The First Detection of an Extragalactic Hot Molecular Core Invited

    Takashi Shimonishi

    The Astronomical Herald   110 ( 6 )   386 - 392   2017.5

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  • Account of "32nd Grain Formation Workshop"

    Kimura Y., Tanaka K. K., Honda M., Sakon I., Miura H.

    Planetary People   25 ( 1 )   21 - 23   2016.3

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    Language:Japanese   Publisher:The Japanese Society for Planetary Sciences  

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  • Report on the 31st Grain Formation Workshop

    Honda M, Sakon I, Kimura Y, Miura H, Shimonishi T, Takigawa A, Tanaka K, Kamizuka T

    Planetary People - The Japanese Society for Planetary Sciences   24 ( 1 )   60 - 62   2015

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  • SPICA MCS Filter Working Groupの活動進捗報告

    左近樹, KEMPER Francisa, 片坐宏一, 和田武彦, 猿楽祐樹, 下西隆, 大藪進喜, 尾中敬, 大山陽一, 松本敏雄, 高見道弘, FOUCAUD Sebastien, ZHAO-GEISLER Ronny, SRINIVASAN Sundar, WU Ronin

    日本天文学会年会講演予稿集   2013   2013

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Presentations

  • Role of Metallicity in the Chemical Evolution of Star-forming Regions Invited

    Takashi Shimonishi

    Kavli-IAU Astrochemistry Symposium  2023.7 

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    Event date: 2023.7

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  • 原始星コアのアストロケミストリーを多様な環境へ

    下西隆

    学術変革領域研究 (A)「次世代アストロケミストリー:素過程理解に基づく学理の再構築」全体集会 2024  2024.3 

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    Event date: 2024.3

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  • 銀河系外縁部/マゼラン雲の低金属量環境下の星間化学 Invited

    下西隆

    天の川銀河研究会2024  2024.3 

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  • 低金属量星形成コアの観測

    High Mass Star Formation Workshop 2024  2024.3 

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  • こんな人探してます

    下西隆

    東北大学 学際科学フロンティア研究所 10周年記念式典  2024.2 

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  • 極めて有機分子の欠乏した銀河系外の原始星に対するALMAラインサーベイ

    下西隆

    VLBI懇談会シンポジウム2023  2023.12 

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    Event date: 2023.12

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  • ALMA View of Molecular Complexity in Low-metallicity Massive Protostellar Cores

    Takashi Shimonishi

    ALMA at 10 years: Past, Present, and Future  2023.12 

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  • 低金属量星形成コアの物理と化学: アルマ観測でどこまで見えてきたか

    下西隆

    新学術領域「星・惑星形成」2023年度大研究会  2023.12 

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  • ALMA Unbiased Spectral Line Survey of an Organic-poor High-mass Protostar in the Large Magellanic Cloud

    Takashi Shimonishi

    Workshop on Interstellar Matter  2023.11 

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  • ALMA view of the chemical complexity in the low-metallicity Universe Invited

    Takashi Shimonishi

    Astronomy, Cosmology & Space Technology Exploration (ACSTEX)  2023.10 

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    Event date: 2023.10

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  • ALMA observations of peculiar embedded icy objects found by the infrared satellite AKARI

    Takashi Shimonishi, Takashi Onaka, Itsuki Sakon, Izumi Endo

    The 13th meeting on Cosmic Dust  2023.8 

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  • ALMA observations of peculiar embedded icy objects found by AKARI

    Takashi Shimonishi, Takashi Onaka, Itsuki Sakon, Izumi Endo

    Protostars and Planets VII  2023.4 

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    Event date: 2023.4

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  • MAGellanic Outflow and chemistry Survey (MAGOS) III: 大小マゼラン雲のホットコアサーベイ

    下⻄ 隆, 田中 圭, Yichen Zhang, 古家 健次

    日本天文学会 春季年会  2023.3 

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    Event date: 2023.3

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  • 低金属量星形成コアの星間化学

    下西 隆

    学術変革領域研究 (A) 「次世代アストロケミストリー: 素過程理解に基づく学理の再構築」全体集会  2023.3 

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  • 過去の宇宙の物質進化を探る –太陽系のように化学的に豊かな系は宇宙史を通して普遍的に存在したのか?–

    下西隆

    量子研究センターキックオフシンポジウム  2023.2 

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    Event date: 2023.2

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  • 低金属量星形成コアの星間化学 -Chemistry of low-metallicity SF cores-

    下西隆

    新学術領域研究 星・惑星形成 2022年度 大研究会  2023.2 

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  • ALMA observations of peculiar embedded icy objects found by AKARI

    Takashi Shimonishi, Takashi Onaka, Itsuki Sakon, Izumi Endo

    A half century of milimeter and submiimeter astronomy: Impact on astronomy/astrophysics and the future  2022.12 

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  • ALMA observations of peculiar embedded icy objects found by AKARI

    T. Shimonishi, T. Onaka, Sakon, I. Endo

    Symposium on Next Generation Astrochemistry  2022.11 

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    Event date: 2022.11 - 2022.12

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  • Peculiar icy objects found by AKARI: Follow-up observations with ALMA

    Takashi Shimonishi, Takashi Onaka, Itsuki Sakon, Izumi Endo

    Molecules in Extreme Environments  2022.11 

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  • ALMA Discovery of the Chemical Complexity in the Outer Part of the Milky Way

    Takashi Shimonishi, Natsuko Izumi, Kenji Furuya, Chikako Yasui

    XXXIst General Assembly of international Astronomical Union (IAUGA 2022)  2022.8 

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    Event date: 2022.8

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  • The Discovery of the Chemical Complexity in the Extreme Outer Galaxy Invited

    44th COSPAR Scientific Assembly  2022.7 

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    Event date: 2022.7

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  • 銀河系の果てから探る過去の宇宙の物質進化 Invited

    下西隆

    日本地球惑星科学連合2022年大会  2022.5 

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    Event date: 2022.5

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  • Chemical Complexity of Star-Forming Regions at Low Metallicity Invited

    Takashi Shimonishi, Ankan Das, Nami Sakai, Kei Tanaka, Yuri Aikawa, Takashi Onaka, Yoshimasa Watanabe, Yuri Nishimura

    43rd COSPAR Scientific Assembly  2021.1 

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    Event date: 2021.1 - 2021.2

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  • From Ice to Gas: Astrochemical perspective in the JWST era and the synergy with ALMA Invited

    Takashi Shimonishi

    ALMA/45m/ASTE Users Meeting FY2020  2021.1 

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    Event date: 2021.1

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  • アルマで探る銀河系最外縁部の星形成と星間物質の化学的多様性

    下西隆

    新学術領域「星惑星形成」2020年度大研究会  2020.9 

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    Event date: 2020.9 - 2020.10

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  • 星形成領域の星間氷観測

    下西隆

    第36回Grain Formation Workshop  2020.2 

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  • ALMA View of Chemistry of Hot Molecular Cores at Low Metallicity

    Takashi Shimonishi

    East-Asian ALMA Science Workshop 2019  2020.2 

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  • Observations of low-metallicity hot cores with ALMA

    下西隆

    大質量形成ワークショップ2020 「大質量星形成研究の現状と次世代観測装置へ向けた展望」  2020.1 

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    Event date: 2020.1

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  • Astrochemistry at the Extreme Outer Galaxy

    Molecular gas observations toward the Local Group and the outer Milky Way  2020.1 

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    Event date: 2020.1

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  • 星間氷に含まれるリンとその観測可能性

    下西隆

    第一回 リンと生命の起源研究会  2019.9 

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    Event date: 2019.9

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  • GREX-PLUSによるマゼラン雲観測 Invited

    下西 隆

    GREX-PLUSサイエンス検討会  2022.3 

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  • LST科学検討報告(アストロケミストリー班)

    下西 隆

    LST白書全班合同ワークショップ  2022.3 

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  • The Detection of a Hot Molecular Core in the Extreme Outer Galaxy

    2022.3 

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  • テラヘルツ観測で探る星形成領域の物質進化 -SPICAから南極へ- Invited

    下西 隆

    南極天文ワークショップ「南極から遠赤外線-テラヘルツ波で探る宇宙」  2022.3 

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  • 銀河系最外縁部における原始星とホットコアのアルマ観測

    下西 隆

    低金属量環境下における星・惑星形成研究会  2021.12 

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  • 共同研究報告:リンと生命の起源

    下西 隆

    連携型博士研究人材総合育成システム 次世代研究者シンポジウム  2021.10 

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  • ALMA Discovery of Chemical Complexity at the Edge of our Galaxy

    Takashi Shimonishi

    Workshop on Interstellar Matter 2021  2021.10 

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  • 銀河系外縁部およびマゼラン雲の星間化学観測

    下西 隆

    学術変革領域研究 (A) 次世代アストロケミストリー 領域全体集会  2021.9 

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  • 観測と星間化学モデルで迫る銀河系外縁部の化学的多様性形成史

    下西 隆

    新学術領域「星惑星形成」後半戦キックオフミーティング  2021.7 

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  • Discovery of a Hot Molecular Core at the Edge of the Galaxy

    Astrochemical Frontiers 2021  2021.7 

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  • Astrochemistry of Low-metallicity Star-forming Regions Invited

    NAOJ Astrochemistry Seminar  2021.2 

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  • Chemistry of star-forming regions at low metallicity Invited

    下西 隆

    国立天文台 科学研究部セミナー  2021.2 

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  • 多波長天文観測による宇宙分子進化史の研究 Invited

    下西隆

    新潟薬科大学 薬学総合セミナー  2020.1 

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  • Physics and Chemistry of a Low-Metallicity Hot Molecular Core in the LMC

    SHIMONISHI Takashi

    2019.9 

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  • NIR-MIR-Radio Spectroscopic Study of Astrochemistry at Low Metallicity International conference

    SHIMONISHI Takashi

    Mid-infrared Astronomy – Past 20 years and Future 20 years  2019.8 

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  • 広視野赤外観測による近傍星形成銀河内の原始星探査 Invited

    下西 隆

    (近)赤外線広視野サイエンスワークショップ ~2020年代に我々はどう主導権を確保するか?~  2019.7 

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  • Astrochemistry under low-metallicity conditions Invited

    SHIMONISHI Takashi

    RIKEN r-EMU seminar  2019.5 

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  • SPICA observations of interstellar chemistry at low metallicity International conference

    SHIMONISHI Takashi

    Exploring the Infrared Universe: The Promise of SPICA  2019.5 

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  • 赤外線天文観測で探る星間氷の諸性質 Invited

    下西 隆

    日本物理学会 第74回年次大会  2019.3 

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  • Observations of hot molecular cores in the Magellanic Clouds: Current status and future prospects International conference

    SHIMONISHI Takashi

    Star formation with ALMA: Evolution from molecular clouds to protostars  2019.3 

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  • 量子化学計算による氷ダスト表面での原子の吸着エネルギー推定と分子雲化学組成への影響の調査

    下西 隆

    第35回 Grain Formation Workshop  2019.2 

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  • Interstellar molecules at low metallicity explored through observations extragalactic star-forming regions Invited International conference

    SHIMONISHI Takashi

    Exploring the Universe: Near Earth space science to extragalactic astronomy  2018.11 

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  • Molecular complexity around a high-mass young stellar object in the Small Magellanic Cloud seen by ALMA

    SHIMONISHI Takashi

    2018.9 

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  • 2030年代に期待する望遠鏡/装置3(星間物質) Invited

    Takashi Shimonishi

    光赤天連シンポジウム2018  2018.9 

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  • The detection of abundant cold methanol gas in the Small Magellanic Cloud International conference

    SHIMONISHI Takashi

    IAU General Assembly Symposium 344 -Dwarf Galaxies: From the Deep Universe to the Present  2018.8 

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  • Organic molecules at 0.2 solar metallicity International conference

    SHIMONISHI Takashi

    The 11th meeting on Cosmic Dust  2018.8 

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  • The detection of abundant cold methanol gas at 0.2 solar metallicity Invited International conference

    SHIMONISHI Takashi

    42nd COSPAR Scientific Assembly  2018.7 

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  • Astrochemical observations of low-metallicity star-forming regions Invited International conference

    SHIMONISHI Takashi

    High Mass Star Formation Workshop 2018  2018.3 

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  • 第一原理計算による星間氷表面への原子の吸着エネルギーの推定 2: 分子雲化学組成への影響

    下西 隆

    日本天文学会春季年会  2018.3 

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  • マゼラン雲の観測で探る低金属量銀河の星間化学 Invited

    下西 隆

    日本天文学会春季年会  2018.3 

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  • Chemical properties of low metallicity star-forming regions Invited International conference

    Takashi Shimonishi

    The 4th AKARI International Conference  2017.10 

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    Venue:JAPAN Tokyo  

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  • Ices in star-forming regions: the role of metallicity Invited International conference

    Takashi Shimonishi

    The 10th meeting on Cosmic Dust  2017.8 

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    Venue:JAPAN 東京  

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  • 赤外線アストロケミストリーの展望 Invited

    光学赤外線天文連絡会シンポジウム 2017  2017.7 

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    Venue:JAPAN 東京  

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  • Observations of a hot molecular core in a low metallicity dwarf galaxy International conference

    Takashi Shimonishi

    IAU Symposium 332, Astrochemistry VII -Through the Cosmos from Galaxies to Planets-  2017.3 

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    Venue:Chile Puerto Varas  

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  • あかりが切り開く銀河系外アストロケミストリーの世界

    下西 隆

    「あかり」サイエンスワークショップ  2016.11 

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  • Observations of ices at low metallicity Invited International conference

    Takashi Shimonishi

    Ice Age -The Era of the James Web Space Telescope-  2016.10 

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    Venue:Netherlands Leiden  

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  • First detection of an extragalactic hot molecular core with ALMA

    Takashi Shimonishi

    日本天文学会秋季年会  2016.9 

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    Venue:JAPAN 松山  

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  • Observations of a hot molecular core in a nearby low metallicity galaxy International conference

    Takashi Shimonishi

    The 9th meeting on Cosmic Dust  2016.8 

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    Venue:JAPAN 仙台  

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  • Observations of a hot molecular core in the Large Magellanic Cloud with ALMA International conference

    Takashi Shimonishi

    Star Formation in Different Environments  2016.7 

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    Presentation type:Poster presentation  

    Venue:Viet Nam Quy Nhon  

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  • 系外銀河における水・有機分子生成

    宇宙生命計算科学連携拠点 第2回ワークショップ  2016.4 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:JAPAN つくば  

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  • Observations of Water and Methanol Ices in the Large Magellanic Cloud International conference

    Takashi Shimonishi

    Water in the Universe: From Clouds to Oceans  2016.4 

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    Venue:Netherlands Leiden  

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  • ALMA Observations of a Hot Molecular Core in the Large Magellanic Cloud International conference

    Takashi Shimonishi

    Molecular Gas in Galactic Environments  2016.4 

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    Venue:United States Charlottesville  

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  • VLT infrared spectroscopic observations of high-mass YSOs in the Large Magellanic Cloud

    Takashi Shimonishi

    第32回Grain Formation Workshop  2015.12 

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    Venue:JAPAN 札幌  

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  • Infrared spectroscopy of embedded high-mass YSOs in the Large Magellanic Cloud: Methanol and the 3.47 mm band International conference

    Takashi Shimonishi

    From Interstellar Ices to Polycyclic Aromatic Hydrocarbons  2015.9 

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    Venue:United States Annapolis  

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  • Infrared spectroscopy in the C--H stretching region towards embedded high-mass young stellar objects in the Large Magellanic Cloud

    Takashi Shimonishi

    日本天文学会秋季年会  2015.9 

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    Venue:JAPAN 兵庫  

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  • Infrared spectroscopy in the C--H stretching region towards embedded high-mass young stellar objects in the Large Magellanic Cloud International conference

    Takashi Shimonishi

    The 8th meeting on Cosmic Dust  2015.8 

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    Venue:JAPAN 東京  

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  • AKARI Infrared Camera Survey of the Large Magellanic Cloud International conference

    Takashi Shimonishi

    国際天文学連合総会  2015.8 

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    Venue:United States Honolulu  

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  • Infrared spectroscopy in the C--H stretching region towards embedded high-mass young stellar objects in the Large Magellanic Cloud International conference

    Takashi Shimonishi

    国際天文学連合総会  2015.8 

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    Venue:United States Honolulu  

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  • Infrared spectroscopy of solid methanol around embedded high-mass YSOs in the LMC

    Takashi Shimonishi

    High-mass star-formation workshop  2015.7 

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    Venue:JAPAN 東京  

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  • Processing of ices in a massive star-forming region

    Takashi Shimonishi

    第31回 Grain Formation Workshop  2015.1 

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    Venue:JAPAN 神奈川  

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  • Molecular cloud chemistry in low metallicity environments - the case of the LMC- International conference

    SHIMONISHI Takashi

    International Conference on Interstellar Dust, Molecules and Chemistry  2014.12 

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  • Processing of ices in a massive star-forming region International conference

    SHIMONISHI Takashi

    Workshop on Interstellar Matter 2014  2014.10 

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  • Spatial Distribution of Ices in a High-mass Star-forming Region International conference

    SHIMONISHI Takashi

    The 7th meeting on Cosmic Dust  2014.8 

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  • A multiwavelength spectroscopic study of molecular chemistry in the Large Magellanic Cloud International conference

    SHIMONISHI Takashi

    THE UNIVERSE IN THE LIGHT OF AKARI and Synergy with future Large Space Telescopes  2014.7 

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  • 大マゼラン雲の分子雲に対する3 mm帯スペクトルラインサーベイ 1. 高密度ガス探査

    SHIMONISHI Takashi

    日本天文学会春季年会  2014.3 

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  • 分子雲の化学進化計算に基づく銀河の環境的要因が氷ダストの化学組成に与える影響の調査

    SHIMONISHI Takashi

    日本天文学会秋季年会  2013.9 

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  • Infrared Observations of Methanol Ice in the Large Magellanic Cloud International conference

    SHIMONISHI Takashi

    The 6th meeting on Cosmic Dust  2013.8 

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  • 赤外線観測に基づくマゼラン雲内の原始星の研究 International conference

    SHIMONISHI Takashi

    ワークショップ「系外銀河の星間化学」  2013.6 

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  • あかり大マセラン雲赤外線点源カタログ II. 分光カタログ

    SHIMONISHI Takashi

    日本天文学会春季年会  2013.3 

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  • Ice Chemistry in the Magellanic Clouds Invited International conference

    SHIMONISHI Takashi

    Workshop on Interstellar Matter 2012  2012.10 

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  • AKARI Near-infrared Spectroscopic Survey of the Large Magellanic Cloud International conference

    SHIMONISHI Takashi

    The Magellanic System: In Perspective  2012.9 

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  • AKARI Near-infrared Spectroscopic Catalog of the Large Magellanic Cloud International conference

    SHIMONISHI Takashi

    COSPAR 2012  2012.7 

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  • Infrared Study of Ices around Young Stellar Objects in the Magellanic Clouds International conference

    SHIMONISHI Takashi

    The Second AKARI Conference, Legacy of AKARI: A Panoramic View of the Dusty Universe  2012.2 

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  • Infrared Observations of Young Stellar Objects outside the Milky Way International conference

    SHIMONISHI Takashi

    International Conference on Interstellar Dust, Molecules and Chemistry  2011.11 

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  • あかりによる大マゼラン雲の点源近赤外分光サーベイ

    SHIMONISHI Takashi

    日本天文学会秋季年会  2011.9 

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  • Effect of Galactic Environment on the Properties of Ices Around Embedded Young Stellar Objects International conference

    SHIMONISHI Takashi

    Asia Oceania Geosciences Society 2011  2011.8 

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  • Infrared Observations of Ices around YSOs in the Large and Small Magellanic Cloud International conference

    SHIMONISHI Takashi

    Workshop of Interstellar Matter 2010  2010.9 

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  • あかり衛星を用いた小マゼラン雲内の若い天体の周囲に存在する氷の近赤外分光観測

    SHIMONISHI Takashi

    日本天文学会秋季年会  2010.9 

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  • Temporal Variations of Near-Infrared Spectra of Carbons Stars in the LMC International conference

    SHIMONISHI Takashi

    Why Galaxies Care About AGB Stars II  2010.8 

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  • Observations of ices around extragalactic young stellar objects by AKARI Invited International conference

    SHIMONISHI Takashi

    Asia Oceania Geosciences Society 2010  2010.7 

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  • あかりで探るdustyな炭素星の近赤外スペクトルの時間変動

    SHIMONISHI Takashi

    スペース赤外線観測による晩期型星研究の現状と将来  2009.12 

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  • Observational Study of Ices around Extragalactic YSOs with AKARI International conference

    SHIMONISHI Takashi

    International Workshop on Interstellar Matter and Star Formation  2009.10 

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  • 「あかり」で探る大マゼラン雲内の炭素星の2-5μmスペクトルに見られる変光の性質

    SHIMONISHI Takashi

    日本天文学会秋季年会  2009.9 

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  • Ices around Extragalactic Young Stellar Objects International conference

    SHIMONISHI Takashi

    42nd International Union of Pure and Applied Chemistry Congress  2009.8 

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  • 2-5 μm Spectroscopic Observations of Ices around Extragalactic Young Stellar Objetcs International conference

    SHIMONISHI Takashi

    AKARI 1st International Conference: a light to illuminate the misty Universe  2009.2 

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  • AKARI Near-Infrared Spectroscopy of Young Stellar Objects in the LMC: Detection of H2O and CO2 ices International conference

    SHIMONISHI Takashi

    IAU Symposium No.256, “The Magellanic System: Stars, Gas, and Galaxies”  2008.8 

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  • AKARI Spectroscopy of YSOs in the Large Magellanic Cloud International conference

    SHIMONISHI Takashi

    AKARI Workshop on Nearby Galaxies, ISM and Stars  2008.3 

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  • AKARI NIR Spectroscopic Survey of the Large Magellanic Cloud -Detection of H2O and CO2 Ice feature-

    SHIMONISHI Takashi

    日本天文学会春季年会  2008.3 

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  • あかり衛星による大マゼラン雲サーベイの初期解析結果 ~銀河系外YSO近赤外スペクトル探査の試み~

    SHIMONISHI Takashi

    日本天文学会秋季年会  2007.9 

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  • あかりIRCによるLMC内のHerbigAe/Be型星近赤外分光観測の展望

    SHIMONISHI Takashi, ONAKA Takashi

    スペースからの赤外線観測による最新の天文学  2007.3 

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Awards

  • 学長賞(若手教員研究奨励)

    2021.10   新潟大学  

    下西隆

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  • Research Associate Professor, Institute for Research Promotion

    2021.8   Niigata University  

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  • 第12回宇宙科学奨励賞

    2020.3   宇宙科学振興会  

    下西隆

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  • Young Chemist Award

    2009.8   42nd IUPAC Congress  

    Takashi Shimonishi

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  • Student Award

    2008.8   IAU Symposium No.256  

    Takashi Shimonishi

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Research Projects

  • Astrochemistry at Low Metallicity

    Grant number:21H01145

    2021.4 - 2024.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

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    Authorship:Principal investigator 

    Grant amount:\16770000 ( Direct Cost: \12900000 、 Indirect Cost:\3870000 )

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  • Chemical Diversity in the Outer Galaxy

    Grant number:21H00037

    2021.4 - 2023.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Awarding organization:Japan Society for the Promotion of Science

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    Authorship:Principal investigator 

    Grant amount:\2600000 ( Direct Cost: \2000000 、 Indirect Cost:\600000 )

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  • Unveiling the physical structure and chemical composition of hot molecular cores by observation and astrochemical model

    2020.7 - 2022.4

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    Authorship:Principal investigator 

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  • 電波および赤外線観測で切り拓く銀河系外縁部の星間化学

    2019.4 - 2021.3

    System name:新学術領域研究(研究領域提案型・公募)

    Awarding organization:文部科学省

    下西 隆

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    Authorship:Principal investigator  Grant type:Competitive

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  • Exploring Chemical Evolution along Formation of Planetary-System by High Resolution/Sensitivity Observations

    Grant number:20H05845

    2020.11 - 2025.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Transformative Research Areas (A)

    Awarding organization:Japan Society for the Promotion of Science

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    Authorship:Coinvestigator(s) 

    Grant amount:\136760000 ( Direct Cost: \105200000 、 Indirect Cost:\31560000 )

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  • 多波長天文観測に基づく低重元素量環境下での星間分子化学の研究

    2015.4 - 2018.3

    System name:科学研究費補助金(若手B)

    Awarding organization:文部科学省

    下西 隆

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    Authorship:Principal investigator  Grant type:Competitive

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  • 異なる金属量環境下における原始星の星周物質の化学的多様性の研究

    2012.4 - 2014.12

    System name:科学研究費補助金(特別研究員奨励費PD)

    Awarding organization:文部科学省

    下西 隆

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    Authorship:Principal investigator  Grant type:Competitive

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  • 銀河系外の若い天体及びその周囲に存在する氷の観測的研究

    2010.4 - 2012.3

    System name:科学研究費補助金(特別研究員奨励費DC2)

    Awarding organization:文部科学省

    下西 隆

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    Authorship:Principal investigator  Grant type:Competitive

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Other research activities

  • 公益財団法人インテリジェントコスモス学術振興財団からの国際学会開催助成(宇宙塵に関する国際研究会"The 9th meeting on Cosmic Dust"の開催支援のため)。

    2016.8

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Teaching Experience (researchmap)

  • Practice of Environmental Science

    2023.10

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  • Environmental Natural Science III

    2023.4

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  • Active Learning

    2023.4

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  • Atomic and Molecular Physics I

    2023.4

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  • Environmental Physics I

    2022

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  • Material Science B

    2022

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  • Environmental natural Science

    2021.4
    -
    2022.3

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  • 数理演習

    2020

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  • 自然環境科学総論

    2020

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  • 基礎ゼミ「Interdisciplinary Sciences ~分野を飛び越えて大学での学びを広げよう~」

    2019

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  • 数理統計学演習

    2017
    -
    2019

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  • 基礎ゼミ「君が天文学者になるセメスター」

    2016
    -
    2017

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  • 天文学セミナー

    2015
    -
    2018

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Teaching Experience

  • 自然環境科学研究演習

    2023
    Institution name:新潟大学

  • 原子分子物理学I

    2023
    Institution name:新潟大学

  • 理学基礎演習

    2022
    Institution name:新潟大学

  • 物質科学B

    2022
    Institution name:新潟大学

  • 環境物理学特論I

    2022
    Institution name:新潟大学

  • 課題研究(自然環境)A

    2022
    Institution name:新潟大学

  • 理学スタディ・スキルズ

    2022
    Institution name:新潟大学

  • 自然環境科学総論

    2021
    Institution name:新潟大学

  • 数理演習

    2020
    Institution name:新潟大学

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