研究者業績

中川 貴雄

ナカガワ タカオ  (Takao Nakagawa)

基本情報

所属
国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所・宇宙物理学研究系 教授
東京大学 大学院理学系研究科 物理学専攻 教授
学位
博士(理学)(東京大学)
修士(理学)(東京大学)

J-GLOBAL ID
200901060914122911
researchmap会員ID
1000363024

外部リンク

委員歴

 3

論文

 395
  • Shusuke Onishi, Takao Nakagawa, Shunsuke Baba, Kosei Matsumoto, Naoki Isobe, Mai Shirahata, Hiroshi Terada, Tomonori Usuda, Shinki Oyabu
    The Astrophysical Journal 2024年11月1日  
  • Hiroto Yanagisawa, Masami Ouchi, Kimihiko Nakajima, Hidenobu Yajima, Hiroya Umeda, Shunsuke Baba, Takao Nakagawa, Minami Nakane, Akinori Matsumoto, Yoshiaki Ono, Yuichi Harikane, Yuki Isobe, Yi Xu, Yechi Zhang
    The Astrophysical Journal 974(2) 180-180 2024年10月1日  
    Abstract We investigate the physical origins of the Balmer decrement anomalies in GS-NDG-9422 and RXCJ2248-ID galaxies at z ∼ 6 whose Hα/Hβ values are significantly smaller than 2.7, the latter of which also shows anomalous Hγ/Hβ and Hδ/Hβ values beyond the errors. Because the anomalous Balmer decrements are not reproduced under the Case B recombination, we explore the nebulae with optical depths smaller and larger than the Case B recombination by physical modeling. We find two cases quantitatively explaining the anomalies: (1) density-bounded nebulae that are opaque only up to around Lyγ–Ly8 transitions and (2) ionization-bounded nebulae partly/fully surrounded by optically thick excited H i clouds. The case of (1) produces more Hβ photons via Lyγ absorption in the nebulae, requiring fine tuning in optical depth values, while this case helps ionizing photon escape for cosmic reionization. The case of (2) needs the optically thick excited Hi clouds with N 2 ≃ 1012−1013 cm−2, where N 2 is the column density of the hydrogen atom with the principal quantum number of n = 2. Interestingly, the high N 2 values qualitatively agree with the recent claims for GS-NDG-9422 with the strong nebular continuum requiring a number of 2s-state electrons and for RXCJ2248-ID with the dense ionized regions likely coexisting with the optically thick clouds. While the physical origin of the optically thick excited H i clouds is unclear, these results may suggest gas clouds with excessive collisional excitation caused by an amount of accretion and supernovae in the high-z galaxies.
  • Takao Nakagawa, Hideo Matsuhara, Umi Enokidani, Toyoaki Suzuki, Shunsuke Baba, Yasuhiro Hirahara, Hidehiro Kaneda, Ryoichi Koga, Yuan Li, Biao Zhao, Daiki Takama, Hiroshi Sasago, Takehiko Wada, Toshihiro Nakaoka, Taiki Eda, Ryota Kakihara, Yoshinori Shohmitsu, Takuya Hosobata, Noboru Ebizuka, Yutaka Yamagata, Shota Notsu, Hideko Nomura
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 236-236 2024年8月23日  
  • Shunsuke Nakagawa, Chinathip Narongphun, Zamba Leonel, Hari Shrestha, Isami Kato, Emino Fukumoto, Rodrigo Cordova, Victor Hugo Schulz, Necmi Cihan Örger, Kei Sano, Takao Nakagawa, Koji Takimoto, Shuji Matsuura, Kohji Tsumura, Aoi Takahashi, Daisuke Nakayama, Akimasa Ojika, Rin Sato, Keenan A. A. Chatar, Yukihisa Otani, Ezra Fielding, Kentaro Hayashida, Hayato Tanaka, Eyoas E. Areda, Bastien B. A. Morelle, Hisataka Kawasaki, Umi Enokidani, Reynel Josue Galindo Rosales, Karaki Shohei, Ichiro Jikuya
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 117-117 2024年8月23日  
  • Hisataka Kawasaki, Eyoas E. Areda, Hideo Matsuhara, Hirokazu Masui, Kohji Takimoto, Bastien B. A. Morelle, Shuji Matsuura, Takao Nakagawa, Umi Enokidani, Yuki Hirose, Kei Sano
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 116-116 2024年8月23日  
  • Hayato Tanaka, Hideo Matsuhara, Takao Nakagawa, Koji Takimoto, Aoi Takahashi, Satoshi Ikari, Rodrigo Cordova, Victor Hugo Schulz, Necmi Cihan Örger, Shunsuke Nakagawa, Shuji Matsuura, Kohji Tsumura
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 115-115 2024年8月23日  
  • Kei Sano, Takao Nakagawa, Shuji Matsuura, Koji Takimoto, Aoi Takahashi, Tetsuhito Fuse, Rodrigo Cordova, Victor Hugo Schulz, Pooja Lepcha, Necmi Cihan Örger, Daisuke Nakayama, Joseph Ofosu, Reynel Josue Galindo Rosales, Eyoas E. Areda, Pema Zangmo, Ezra Fielding, Keenan A. A. Chatar, Yukihisa Otani, Hisataka Kawasaki, Bastien B. A. Morelle, John Almonte, Shunsuke Nakagawa, Yuto Tome, Shohei Karaki, Chinathip Narongphun, Hari Shrestha, Marco Rosa, David Dai, Wenceslao Bejarano, Akihiro Ikeda, Rin Sato, Kentaro Hayashida, Hiroki Miyagawa, Masahiro Nishioka, Kana Kurosaki, Isami Kato, Satoshi Ikari, Kohji Tsumura, Ichiro Jikuya, Hideo Matsuhara, Umi Enokidani, Hayato Tanaka, Yuki Hirose, Akimasa Ojika, Akane Tsumoto, Taiko Iwaki, Yuki Ohara, Mengu Cho, Kentaro Kitamura, Hirokazu Masui, Mariko Teramoto, Takashi Yamauchi, Ryo Hashimoto, Emino Fukumoto, Zamba Leonel, Arisa Oho, Shoki Yabumoto, Hayato Masuno, Chisato Arakawa, Kouta Miyamoto, Takehiko Wada, Naoki Isobe, Yasuyuki Miyazaki, Ryu Funase, Hajime Kawahara, Keiichi Hirako, Yoichi Yatsu, Yoshihide Aoyanagi
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 33-33 2024年8月23日  
  • Koji Takimoto, Yuki Hirose, Taiko Iwaki, Hisataka Kawasaki, Shuji Matsuura, Shunsuke Nakagawa, Takao Nakagawa, Akimasa Ojika, Rin Sato, Aoi Takahashi, Yuto Tome, Akane Tsumoto, Kohji Tsumura, Kei Sano
    Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave 34-34 2024年8月23日  
  • Thomas S.-Y. 劭愉 Lai 賴, J. D. T. Smith, Els Peeters, Henrik W. W. Spoon, Shunsuke 俊介 Baba 馬場, Masatoshi 昌俊 Imanishi 今西, Takao 貴雄 Nakagawa 中川
    The Astrophysical Journal 2024年6月1日  
  • Kosei Matsumoto, Peter Camps, Maarten Baes, Frederik De Ceuster, Keiichi Wada, Takao Nakagawa, Kentaro Nagamine
    Astronomy & Astrophysics 2023年10月  
  • Naoki Isobe, Hiroshi Nagai, Motoki Kino, Shunsuke Baba, Takao Nakagawa, Yuji Sunada, Makoto Tashiro
    The Astrophysical Journal 2023年8月1日  
  • Youichi Ohyama, Shusuke Onishi, Takao Nakagawa, Kosei Matsumoto, Naoki Isobe, Mai Shirahata, Shunsuke Baba, Kazushi Sakamoto
    The Astrophysical Journal 2023年7月1日  
  • Taichi Uyama, Charles Beichman, Masayuki Kuzuhara, Markus Janson, Takayuki Kotani, Dimitri Mawet, Bun’ei Sato, Motohide Tamura, Hiroyuki Tako Ishikawa, Bryson Cale, Thayne Currie, Hiroki Harakawa, Thomas Henning, Teruyuki Hirano, Klaus Hodapp, Yasunori Hori, Masato Ishizuka, Shane Jacobson, Yui Kasagi, Eiichiro Kokubo, Mihoko Konishi, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Jungmi Kwon, Masahiro Machida, Takao Nakagawa, Norio Narita, Jun Nishikawa, Masahiro Ogihara, Masashi Omiya, Takuma Serizawa, Akitoshi Ueda, Sébastien Vievard, Ji Wang
    The Astronomical Journal 165(4) 162-162 2023年3月17日  
    Abstract The Subaru telescope is currently performing a strategic program (SSP) using the high-precision near-infrared (NIR) spectrometer IRD to search for exoplanets around nearby mid/late M dwarfs via radial velocity (RV) monitoring. As part of the observing strategy for the exoplanet survey, signatures of massive companions such as RV trends are used to reduce the priority of those stars. However, this RV information remains useful for studying the stellar multiplicity of nearby M dwarfs. To search for companions around such “deprioritized” M dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2 with pyramid wave-front sensing at NIR wavelengths, leading to high sensitivity to substellar-mass companions within a few arcseconds. We detected two new companions (LSPM J1002+1459 B and LSPM J2204+1505 B) and two new candidates that are likely companions (LSPM J0825+6902 B and LSPM J1645+0444 B), as well as one known companion. Including two known companions resolved by the IRD fiber injection module camera, we detected seven (four new) companions at projected separations between ∼2 and 20 au in total. A comparison of the colors with the spectral library suggests that LSPM J2204+1505 B and LSPM J0825+6902 B are located at the boundary between late M and early L spectral types. Our deep high-contrast imaging for targets where no bright companions were resolved did not reveal any additional companion candidates. The NIRC2 detection limits could constrain potential substellar-mass companions (∼10–75 MJup) at 10 au or further. The failure with Keck/NIRC2 around the IRD-SSP stars having significant RV trends makes these objects promising targets for further RV monitoring or deeper imaging with the James Webb Space Telescope to search for smaller-mass companions below the NIRC2 detection limits.
  • Hyunjin Shim, Ho Seong Hwang, Woong-Seob Jeong, Yoshiki Toba, Minjin Kim, Dohyeong Kim, Hyunmi Song, Tetsuya Hashimoto, Takago Nakagawa, Ambra Nanni, William J. Pearson, Toshinobu Takagi
    The Astronomical Journal 2023年2月1日  
  • Keisuke Shinozaki, Yoichi Sato, Haruka Fukuoka, Chihiro Tokoku, Takao Nakagawa, Hiroyuki Sugita, Shoji Tsunematsu, Kenichi Kanao, Katsuhiro Narasaki
    Cryogenics 128 103575-103575 2022年12月  
  • 戸部裕史, 石川和毅, 澤田健一郎, 東谷千比呂, 東谷千比呂, 中川貴雄, 佐藤英一
    銅と銅合金 61(1) 334-338 2022年8月  査読有り
  • Hiroki Harakawa, Takuya Takarada, Yui Kasagi, Teruyuki Hirano, Takayuki Kotani, Masayuki Kuzuhara, Masashi Omiya, Hajime Kawahara, Akihiko Fukui, Yasunori Hori, Hiroyuki Tako Ishikawa, Masahiro Ogihara, John Livingston, Timothy D. Brandt, Thayne Currie, Wako Aoki, Charles A. Beichman, Thomas Henning, Klaus Hodapp, Masato Ishizuka, Hideyuki Izumiura, Shane Jacobson, Markus Janson, Eiji Kambe, Takanori Kodama, Eiichiro Kokubo, Mihoko Konishi, Vigneshwaran Krishnamurthy, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Jungmi Kwon, Yuji Matsumoto, Michael W. McElwain, Koyu Mitsui, Takao Nakagawa, Norio Narita, Jun Nishikawa, Stevanus K. Nugroho, Eugene Serabyn, Takuma Serizawa, Aoi Takahashi, Akitoshi Ueda, Taichi Uyama, Sebastien Vievard, Ji Wang, John Wisniewski, Motohide Tamura, Bun'ei Sato
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 74(4) 904-922 2022年8月  
    We report the near-infrared radial velocity (RV) discovery of a super-Earth planet on a 10.77 d orbit around the M4.5 dwarf Ross 508 (J(mag) = 9.1). Using precision RVs from the Subaru Telescope IRD (InfraRed Doppler) instrument, we derive a semi-amplitude of 3.92(-0.58)(+0.60) m s(-1), corresponding to a planet with a minimum mass msin i = 4.00(-0.55)(+0.53) M-circle plus. We find no evidence of significant signals at the detected period in spectroscopic stellar activity indicators or MEarth photometry. The planet, Ross 508 b, has a semi-major axis of 0.05366(-0.00049)(+0.00056) au. This gives an orbit-averaged insolation of approximate to 1.4 times the Earth's value, placing Ross 508 b near the inner edge of its star's habitable zone. We have explored the possibility that the planet has a high eccentricity and its host is accompanied by an additional unconfirmed companion on a wide orbit. Our discovery demonstrates that the near-infrared RV search can play a crucial role in finding a low-mass planet around cool M dwarfs like Ross 508.
  • Kosei Matsumoto, Takao Nakagawa, Keiichi Wada, Shunsuke Baba, Shusuke Onishi, Taisei Uzuo, Naoki Isobe, Yuki Kudoh
    The Astrophysical Journal 934(1) 25-25 2022年7月1日  
    Abstract A recent hydrodynamic model, the radiation-driven fountain model (Wada et al. 2016), presented a dynamical picture that active galactic nuclei (AGNs) tori sustain their geometrical thickness by gas circulation around AGNs, and previous papers have confirmed that this picture is consistent with multiwavelength observations of nearby Seyfert galaxies. Recent near-infrared observations implied that CO rovibrational absorption lines (ΔJ = ± 1, v = 0 − 1, λ ∼ 4.7 μm) could probe the physical properties of the inside tori. However, the origin of the CO absorption lines has been under debate. In this paper, we investigate the origin of the absorption lines and conditions for detecting them by performing line radiative transfer calculations based on the radiation-driven fountain model. We find that CO rovibrational absorption lines are detected at inclination angles θobs = 50°–80°. At the inclination angle θobs = 77°, we observe multi-velocity components: inflow (vLOS = 30 km s−1), systemic (vLOS = 0 km s−1), and outflows (vLOS = −75, − 95, and −105 km s−1). The inflow and outflow components (vLOS = 30 and −95 km s−1) are collisionally excited at the excitation temperatures of 186 and 380 K up to J = 12 and 4, respectively. The inflow and outflow components originate from the accreting gas on the equatorial plane at 1.5 pc from the AGN center and the outflowing gas driven by AGN radiation pressure at 1.0 pc, respectively. These results suggest that CO rovibrational absorption lines can provide us with the velocities and kinetic temperatures of the inflow and outflow in the inner few parsec region of AGN tori, and the observations can probe the gas circulation inside the tori.
  • 山岸 光義, 山村 一誠, 大薮 進喜, 大坪 貴文, 和田 武彦, 石原 大助, 中川 貴雄, 金田 英宏, 平原 靖大
    宇宙航空研究開発機構研究開発報告 JAXA-RR-21-007E 1-35 2022年2月  査読有り
  • Hiroyuki Tako Ishikawa, Wako Aoki, Teruyuki Hirano, Takayuki Kotani, Masayuki Kuzuhara, Masashi Omiya, Yasunori Hori, Eiichiro Kokubo, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Norio Narita, Jun Nishikawa, Masahiro Ogihara, Akitoshi Ueda, Thayne Currie, Thomas Henning, Yui Kasagi, Jared R. Kolecki, Jungmi Kwon, Masahiro N. Machida, Michael W. McElwain, Takao Nakagawa, Sebastien Vievard, Ji Wang, Motohide Tamura, Bun'ei Sato
    ASTRONOMICAL JOURNAL 163(2) 2022年2月  
    Detailed chemical analyses of M dwarfs are scarce but necessary to constrain the formation environment and internal structure of planets being found around them. We present elemental abundances of 13 M dwarfs (2900 < T (eff) < 3500 K) observed in the Subaru/IRD planet search project. They are mid- to late-M dwarfs whose abundance of individual elements has not been well studied. We use the high-resolution (similar to 70,000) near-infrared (970-1750 nm) spectra to measure the abundances of Na, Mg, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Sr by the line-by-line analysis based on model atmospheres, with typical errors ranging from 0.2 dex for [Fe/H] to 0.3-0.4 dex for other [X/H]. We measure radial velocities from the spectra and combine them with Gaia astrometry to calculate the Galactocentric space velocities UVW. The resulting [Fe/H] values agree with previous estimates based on medium-resolution K-band spectroscopy, showing a wide distribution of metallicity (-0.6 < [Fe/H] < +0.4). The abundance ratios of individual elements [X/Fe] are generally aligned with the solar values in all targets. While the [X/Fe] distributions are comparable to those of nearby FGK stars, most of which belong to the thin-disk population, the most metal-poor object, GJ 699, could be a thick-disk star. The UVW velocities also support this. The results raise the prospect that near-infrared spectra of M dwarfs obtained in the planet search projects can be used to grasp the trend of elemental abundances and the Galactic stellar population of nearby M dwarfs.
  • Hiroshi Maeshima, Kosei Matsumoto, Yasuhiro Hirahara, Takao Nakagawa, Ryoichi Koga, Yusuke Hanamura, Takehiko Wada, Koichi Nagase, Shinki Oyabu, Toyoaki Suzuki, Takuma Kokusho, Hidehiro Kaneda, Daichi Ishikawa
    JOURNAL OF ELECTRONIC MATERIALS 51(2) 564-576 2022年2月  
    To reveal the causes of infrared absorption in the wavelength region between electronic and lattice absorptions, we measured the temperature dependence of the absorption coefficient of p-type low-resistivity (similar to 10(2) Omega cm) CdZnTe crystals. We measured the absorption coefficients of CdZnTe crystals in four wavelength bands (lambda = 6.45, 10.6, 11.6, 15.1 mu m) over the temperature range of T = 8.6-300 K with an originally developed system. The CdZnTe absorption coefficient was measured to be alpha = 0.3-0.5 cm(-1) at T = 300 K and alpha = 0.4-0.9 cm(-1) at T = 8.6 K in the investigated wavelength range. With an absorption model based on transitions of free holes and holes trapped at an acceptor level, we conclude that the absorption due to free holes at T = 150-300 K and that due to trapped-holes at T < 50 K are dominant absorption causes in CdZnTe. We also discuss a method to predict the CdZnTe absorption coefficient at cryogenic temperature based on the room-temperature resistivity.
  • Hideki Uchida, Tadahito Mizutani, Susumu Yasuda, Takao Nakagawa, Shinsuke Takeuchi, Hidehiro Kaneda, Kazuki Watanabe, Takeshi Kuratomi
    AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2022 2022年  
    The application of superelastic alloys to microvibration isolators for a spacecraft was studied. The superelastic alloy in this study is characterized by a wide hysteresis loop in the stress-strain curve, which dissipates a large amount of energy even with a slight change in stress. Prototype struts with damping mechanisms utilizing such characteristics were developed, and an isolation system consisting of the damping struts was investigated. The isolation system was designed to satisfy the requirements of the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), which has several mechanical cryocoolers to cool down the entire telescope to cryogenic temperature. Since the vibrations generated by the cryocoolers can be transmitted to the telescope and deteriorate the pointing stability, SPICA is designed to integrate all cryocoolers into cooler plates and isolate the plates from vibrations with the isolation system. The simulation method to design the isolation system was developed and validated by comparing the estimation with the test results of a bipod with a pair of the damping struts.
  • Hiroshi Maeshima, Takao Nakagawa, Takuya Kojima, Satoshi Takita, Jungmi Kwon
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 73(6) 1589-1603 2021年12月  
    Dust and gas in protoplanetary disks dissipate as central stars evolve. In order to estimate the dust dissipation timescales in the protoplanetary disks, we stacked the WISE 12 and 22, and the AKARI 90 mu m survey images of known T Tauri stars and derived the average fluxes, well below the survey flux limit in the 90 mu m band. We classified 4783 T Tauri stars into three age groups, which are young (<2 Myr), mid-age (2-6 Myr), and old (>6 Myr) groups, and stacked the WISE 12 and 22 and the AKARI 90 mu m images in each group. The photometry of the stacked image shows the flux decay timescales of 1.4 +/- 0.2, 1.38 +/- 0.05, and 1.4(-0.5)(+0.6) Myr in the 12, 22, and 90 mu m bands, respectively. In optically thin disks with one-solar luminosity central stars, the 12 and 22 mu m fluxes are attributed to the emission from the intermediate (similar to 1 au) region and the 90 mu m flux corresponds to that from the outer (similar to 10 au) region in the disk. We hence conclude that the dust dissipation timescale is tau(med,dust) similar to 1.4 Myr in the intermediate disks and is tau(outer.dust) = 1.4(-0.5)(+0.6) Myr in the outer disks. The dust-dissipation time difference between the outer and intermediate disks is Delta tau(dust) = tau(outer.dust) - tau(med,dust) = 0.0(-0.5)(+0.6) Myr, indicating that the dust in the intermediate and outer disks dissipates on almost the same timescale.
  • Kenichi Yano, Shunsuke Baba, Takao Nakagawa, Matthew A. Malkan, Naoki Isobe, Mai Shirahata, Ryosuke Doi, Vanshree Bhalotia
    ASTROPHYSICAL JOURNAL 922(2) 2021年12月  
    We conducted systematic observations of the H i Br alpha (4.05 mu m) and Br beta (2.63 mu m) lines in 52 nearby (z < 0.3) ultraluminous infrared galaxies (ULIRGs) with AKARI. Among 33 ULIRGs wherein the lines are detected, 3 galaxies show anomalous Br beta/Br alpha line ratios (similar to 1.0), which are significantly higher than those for case B (0.565). Our observations also show that ULIRGs have a tendency to exhibit higher Br beta/Br alpha line ratios than those observed in Galactic H ii regions. The high Br beta/Br alpha line ratios cannot be explained by a combination of dust extinction and case B since dust extinction reduces the ratio. We explore possible causes for the high Br beta/Br alpha line ratios and show that the observed ratios can be explained by a combination of an optically thick Br alpha line and an optically thin Br beta line. We simulated the H ii regions in ULIRGs with the Cloudy code, and our results show that the high Br beta/Br alpha line ratios can be explained by high-density conditions, wherein the Br alpha line becomes optically thick. To achieve a column density large enough to make the Br alpha line optically thick within a single H ii region, the gas density must be as high as n similar to 10(8) cm(-3). We therefore propose an ensemble of H ii regions, in each of which the Br alpha line is optically thick, to explain the high Br beta/Br alpha line ratio.
  • Inga 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年11月3日  
    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. SPace Infrared telescope for Cosmology and Astrophysics (SPICA) 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 SPICA that enable this research are (1) the wide spectral coverage, (2) the high line detection sensitivity of with in the far-IR (SAFARI), and with in the mid-IR (SPICA 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 months of observing time.
  • Shusuke Onishi, Takao Nakagawa, Shunsuke Baba, Kosei Matsumoto, Naoki Isobe, Mai Shirahata, Hiroshi Terada, Tomonori Usuda, Shinki Oyabu
    ASTROPHYSICAL JOURNAL 921(2) 2021年11月  
    Understanding the inner structure of the clumpy molecular torus surrounding the active galactic nucleus is essential in revealing the forming mechanism However, spatially resolving the torus is difficult because of its size of a few parsecs. Thus, to probe the clump conditions in the torus, we performed the velocity decomposition of the CO rovibrational absorption lines (Delta nu = 0 -> 1, Delta J= +/- 1) at lambda similar to 4.67 mu m observed toward an ultraluminous infrared galaxy IRAS 08572+3915 NW with the high-resolution spectroscopy (R similar to 10,000) of Subaru Telescope. Consequently, we found that each transition had two outflowing components, i.e., (a) and (b), both at approximately similar to-160 km s(-1), but with broad and narrow widths, and an inflowing component, i.e., (c), at approximately similar to+100 km s(-1), which were attributed to the torus. The ratios of the velocity dispersions of each component led to those of the rotating radii around the black hole of R-rot,R-a: R-rot,R-b: R-rot,R-c approximate to 1: 5: 17, indicating the torus where clumps are outflowing in the inner regions and inflowing in the outer regions if a hydrostatic disk with sigma(V) proportional to R-rot(-0.5) is assumed. Based on the kinetic temperature of components (a) and (b) of similar to 720 and similar to 25 K, respectively, estimated from the level population, the temperature gradient is T-kin proportional to R-rot(-)2.1. Magnetohydrodynamic models with large density fluctuations of two orders of magnitude or more are necessary to reproduce this gradient.
  • T. Suzuki, S. Oyabu, S. K. Ghosh, D. K. Ojha, H. Kaneda, H. Maeda, T. Nakagawa, J. P. Ninan, S. Vig, M. Hanaoka, F. Saito, S. Fujiwara, T. Kanayama
    Astronomy and Astrophysics 651 2021年7月1日  
    Aims. We investigate the properties of [C II] 158 μm emission of RCW 36 in a dense filamentary cloud. Methods. [C II] observations of RCW 36, covering an area of ~30′ × 30′, were carried out with a Fabry-Pérot spectrometer on board a 100-cm balloon-borne far-infrared (IR) telescope with an angular resolution of 90′′. Using AKARI and Herschel images, we compared the spatial distribution of the [C II] intensity with the emission from the large grains and polycyclic aromatic hydrocarbon (PAH). Results. The [C II] emission is in good spatial agreement with shell-like structures of a bipolar lobe observed in IR images, which extend along the direction perpendicular to the direction of cold dense filament. We found that the [C II]-160 μm relation for RCW 36 shows a higher brightness ratio of [C II]/160 μm than that for RCW 38, while the [C II]-9 μm relation for RCW 36 is in good agreement with that for RCW 38. Conclusions. Via a spectral decomposition analysis on a pixel-by-pixel basis using IR images, the [C II] emission is spatially well correlated with PAH and cold dust emissions. This means that the observed [C II] emission predominantly comes from photo-dissociation regions. Moreover, the L[C II]LFIR ratio shows large variation (10-2-10-3), as compared with the L[C II]/LPAH ratio. In view of the observed tight correlation between L[C II]LFIR and the optical depth at λ = 160 μm, the large variation in L[C II]LFIR can be simply explained by the geometrical effect, that is, LFIR has contributions from the entire dust-cloud column along the line of sight, while L[C II] has contributions from far-UV illuminated cloud surfaces. Based on the picture of the geometry effect, the enhanced brightness ratio of [C II]/160 μm is attributed to the difference in gas structures where massive stars are formed: filamentary (RCW 36) and clumpy (RCW 38) molecular clouds; thus suggesting that RCW 36 is dominated by far-UV illuminated cloud surfaces, as compared with RCW 38.
  • Yoichi Sato, Kosuke Tanaka, Hiroyuki Sugita, Keisuke Shinozaki, Kenichiro Sawada, Noriko Y. Yamasaki, Takao Nakagawa, Kazuhisa Mitsuda, Shoji Tsunematsu, Kiyomi Ootsuka, Kenichi Kanao, Katsuhiro Narasaki
    CRYOGENICS 116 2021年6月  
    The 4K Joule-Thomson (JT) cryocooler is a key cryogenic component for future astronomy missions such as ATHENA and LiteBIRD. It was originally developed for SMILES (2009) and upgraded for ASTRO-H/SXS (2016) and SPICA. The 20K two-stage Stirling cryocooler developed for AKARI (2006) was also upgraded and used as a precooler. The operational life is a critical factor in planning long-term missions. An engineering model of the 4KJT cryocooler was built for continuous operation to verify its lifetime. Testing was done from 2010 to 2019 and successful three-year operation was demonstrated with an extended operation; this was beyond the design specification. This paper describes the overall history of the lifetime test of the 4K-JT cryocooler and an evaluation of the end-of-life cooling performance and performance changes during long-term operation.
  • T. Prouvé, J. M. Duval, I. Charles, N. Y. Yamasaki, K. Mitsuda, T. Nakagawa, K. Shinozaki, C. Tokoku, R. Yamamoto, Y. Minami, M. Le Du, J. Andre, C. Daniel, M. Linder
    Cryogenics 112 2020年12月  
    In the framework of the ESA X-ray mission ATHENA, scheduled for launch in 2030, an ESA Core Technology Program (CTP) was started in 2016 to build a flight like cryostat demonstrator in parallel with the phase A studies of the ATHENA/X-IFU instrument. As part of this CTP, called the Detector Cooling System (DCS), design, manufacturing and test of a cryostat including existing space coolers will be done. In addition to the validation of thermal performance, a Focal Plan Assembly (FPA) demonstrator using Transition Edge Sensors (TES) detector technology will be also integrated and its performance characterized versus the environment provided by the cryostat. This is a unique opportunity to validate many crucial issues of the cryogenic part of such a sensitive instrument. A dedicated activity within this CTP-DCS is the demonstration of the 300 K–50 mK cooling chain in a Ground System Equipment (GSE) cryostat. The studies are focused on the operation of the space coolers, which is made possible by the use of a ground cooler for cooling cryogenic shields and mechanical supports. This test program is also the opportunity to validate the operation of the cryochain with respect to various requirements, such as time constant and temperature stabilities. This would bring us valuable inputs to integrate the cryochain in DCS cryostat, X-IFU studies, SPICA and LiteBIRD missions. This paper is focused on the operation of the full 300 K–50 mK cryochain. In particular, the recycling options of the sub Kelvin cooler (sorption cooler + an ADR) versus the capability of 4 K and 2 K JT coolers are described. Results on the JT parameters validation campaign are summarized and eventually the results of the coupled test with sub Kelvin cooler will be presented and discussed.
  • Il Joong Kim, Jeonghyun Pyo, Woong Seob Jeong, Kwang Il Seon, Takao Nakagawa, Min Gyu Kim, Won Kee Park, Dae Hee Lee, Dukhang Lee, Bongkon Moon, Sung Joon Park, Youngsik Park, Toshio Matsumoto, Wonyong Han
    Astrophysical Journal, Supplement Series 251(1) 2020年11月  
    In published article, we did not take into account that the [N II] λλ6548, 6584 A lines are within the wavelength range of the IPHAS Hα filter. The [N II] to Hα line ratio observed for the H II regions in our Galaxy is not negligible ([N II]/Hα ≈ 0.25; Haffner et al. 2009). Therefore, in this erratum, we correct the Hα fluxes of the H II regions (or candidates) estimated in the published article (Figur Presented) by eliminating the [N II] contributions to the IPHAS Hα. Although there is the radial abundance gradient of N/H in our Galaxy (Esteban & García-Rojas 2018), the directions of the H II regions in this study (ℓ = 96°-116°) are not largely different from those of Haffner et al. (2009) (ℓ = 130°-160°). So, we assumed the line ratio of [N II]/Hα ≈ 0.25 for the correction. Additionally, according to Barentsen et al. (2014), the Hα magnitude for Vega is conventionally set to 0.03 mag. Therefore, we adopted the Vega Hα magnitude of 0.03 mag, instead of 0 mag in the published article, for the calculations of the IPHAS Hα fluxes, though this effect is not large compared to the effects of the other changes. In this erratum, we also apply the recently updated calibration factors for the MIPAPS data (27.8 ± 2.0 mJy (ADU s-1)-1 for PAAL and 17.2 ± 1.2 mJy (ADU s-1)-1 for PAAC; I.-J. Kim et al. 2020, in preparation) to the measurements of the Paα fluxes. In the published article, we used the calibration factors of 23.7 ± 0.1 and 14.6 ± 0.1 mJy (ADU s-1)-1, respectively.
  • Il-Joong Kim, Jeonghyun Pyo, Woong-Seob Jeong, Kwang-Il Seon, Takao Nakagawa, Min Gyu Kim, Won-Kee Park, Dae-Hee Lee, Dukhang Lee, Bongkon Moon, Sung-Joon Park, Youngsik Park, Toshio Matsumoto, Wonyong Han
    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 251(1) 2020年11月  
  • Kiyomi Otsuka, Ken'ichi Kanao, Shoji Tsunematsu, Katsuhiro Narasaki, Yoshikatsu Hiratsuka, Noriko Yamasaki, Kazuhisa Mitsuda, Takao Nakagawa, Keisuke Shinozaki, Yoichi Sato
    Cryogenics 111 2020年10月  
    Two-stage Stirling cryocoolers (2ST cooler) produced by Sumitomo Heavy Industries, Ltd. have been launched into orbit on three satellites: the “AKARI (ASTRO-F)” infrared astronomical satellite, JEM/SMILES on ISS, and the “HITOMI (ASTRO-H)” X-ray astronomical satellite. A 2ST cooler compressor has a linear-ball-bearing system as a piston-supporting structure. The linear ball bearing system is a key components to realize a lower drive frequency (15 Hz), a long piston stroke (30 mm). Its typical cooling power is 200 mW at 20 K for the second stage and 1000 mW at 100 K for the first stage, with 90 W electrical input power. During the test of the “HITOMI” engineering model, the energy resolution of the detector was found to be degraded when cryocoolers were in operation. After investigation, it was found that micro vibration from 2STs caused the degradation. The continuum in the vibration spectrum propagated into sub-Kelvin region and generated thermal noise. The continuum has origin in linear ball bearing in the compressor. In the case of “HITOMI”, vibration isolators were introduced to resolve this issue. For future mission, we are required to reduce microvibration of cryocooler itself. Therefore, the piston support mechanism in the compressor was modified from linear ball bearings to triangle shape flexure springs in order to reduce the continuum in vibration spectrum. In order to achieve a long piston stroke (±15 mm), the generated stress could be reduced to 400 MPa (Less than 1/2 of fatigue limit) or less even when the shape of the triangle shape flexure spring was devised and displaced by 15 mm. The typical vibration level has been reduced to 1 × 10 Nrms / Hz or less at a frequency of 200 Hz or less and 1/10 times or less at 200–600 Hz than that of a compressor with a linear ball bearing system. The cooling power is kept to 260 mW at 20 K, with 90 W electrical input power. This low vibration cooler is expected to be an improved cryogenic system for use in future projects with sub-Kelvin detectors. −5 2
  • Keisuke Shinozaki, Yoichi Sato, Kenichiro Sawada, Hiroyuki Sugita, Takao Nakagawa, Chihiro Tokoku, Noriko Y. Yamasaki, Kazuhisa Mitsuda, Shoji Tsunematsu, Kenichi Kanao, Thomas Prouvé, Jean Marc Duval, Ivan Charles
    Cryogenics 109 2020年7月  
    In space science missions that uses cryogen-free mechanical cooler systems to cool the low temperature telescope and detectors, a cooling time from room temperature to low temperature should be considered in the required mission life time, because of a limited cooling power of mechanical cooler. For instance, in the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the 4K-class Joule Thomson cooler (4K-JT) and the 1K-class Joule Thomson cooler (1K-JT) are being considered to cool a 2.5 m telescope and provide a 1–4 K environment for scientific instruments. The cooling capability of these JT coolers, below 20 K and even lower than 5 K, is critical for initial cooling. The 4K-JT cooling from precooling to operating temperatures under the heat input was measured and confirmed that the 4K-JT has enough cooling power to cool with these heat load. The 1K-JT cool down measurement with heater was also performed. These results enabled us to estimate the cool down time for the heat capacity provided by the telescope and scientific instruments assumed in SPICA, LiteBIRD and the ESA X-ray mission ATHENA.
  • Yi Yang, Eiji Akiyama, Thayne Currie, Ruobing Dong, Jun Hashimoto, Saeko S. Hayashi, Carol A. Grady, Markus Janson, Nemanja Jovanovic, Taichi Uyama, Takao Nakagawa, Tomoyuki Kudo, Nobuhiko Kusakabe, Masayuki Kuzuhara, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Michael Bonnefoy, Joseph C. Carson, Jeffrey Chilcote, Evan A. Rich, Markus Feldt, Miwa Goto, Tyler D. Groff, Olivier Guyon, Yutaka Hayano, Masahiko Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Ryo Kandori, Jeremy Kasdin, Gillian R. Knapp, Jungmi Kwon, Julien Lozi, Frantz Martinache, Taro Matsuo, Satoshi Mayama, Michael W. McElwain, Shoken Miyama, Jun Ichi Morino, Amaya Moro-Martin, Tetsuo Nishimura, Tae Soo Pyo, Eugene Serabyn, Hiroshi Suto, Ryuji Suzuki, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Edwin L. Turner, Makoto Watanabe, John P. Wisniewski, Toru Yamada, Hideki Takami, Tomonori Usuda, Motohide Tamura
    Astrophysical Journal 889(2) 2020年2月1日  
    We analyzed the young (2.8 Myr-old) binary system FS Tau A using near-infrared (H-band) high-contrast polarimetry data from Subaru/HiCIAO and submillimeter CO (J = 2-1) line emission data from Atacama Large Millimeter/submillimeter Array (ALMA). Both the near-infrared and submillimeter observations reveal several clear structures extending to ∼240 au from the stars. Based on these observations at different wavelengths, we report the following discoveries. One arm-like structure detected in the near-infrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to two bar-like structures detected in ALMA observations with an local standard of rest kinematic (LSRK) velocity of 1.19-5.64 km s . Another feature detected in the near-infrared band extends initially from the north of the binary, relating to an arm-like structure detected in ALMA observations with an LSRK velocity of 8.17-16.43 km s . From their shapes and velocities, we suggest that these structures can mostly be explained by two streamers that connect the outer circumbinary disk and the central binary components. These discoveries will be helpful for understanding the evolution of streamers and circumstellar disks in young binary systems. -1 -1
  • Takehiko Wada, Hidehiro Kaneda, Takuma Kokusho, Toyoaki Suzuki, Kumiko Morihana, Takurou Tsuchikawa, Yuki Kuroda, Daichi Ishikawa, Shinki Oyabu, Naoki Isobe, Daisuke Ishihara, Hideo Matsuhara, Koichi Nagase, Takao Nakagawa, Takafumi Ootsubo, Mitsuyoshi Yamagishi, Hiroshi Maeshima, Shunsuke Onishi, Kosei Matsumoto, Satoshi Itoh, Mizuho Uchiyama, Ryan Lau, Hiromichi Ebihara, Hanae Inami, Koji Kawabata, Yasumasa Kasaba, Takeshi Sakanoi, Yoshifusa Ita, Masayuki Akiyama, Itsuki Sakon, Takafumi Kamizuka, Takashi Miyata, Kohji Tsumura, Masato Naruse, Youichi Ohyama, Shiang Yu Wang, Hiroshi Shibai
    Proceedings of SPIE - The International Society for Optical Engineering 11443 2020年  
    SMI (SPICA Mid-infrared Instrument) is one of the three focal-plane science instruments for SPICA. SMI is the Japanese-led instrument proposed and managed by a university consortium. SMI covers the wavelength range from 10 to 36 μm with four separate channels: the low-resolution (R = 60 - 160) spectroscopy function for 17 - 36 μm, the broad-band (R = 5) imaging function at 34 μm, the mid-resolution (R = 1400 - 2600) spectroscopy function for 18 - 36 μm, and the high-resolution (R = 29000) spectroscopy function for 10 - 18 μm. In this presentation, we will show the latest design and specifications of SMI as a result of feasibility studies.
  • Takao Nakagawa, Ken Goto, Hidehiro Kaneda, Hideo Matsuhara, Jun Matsumoto, Tadahito Mizutani, Hiroyuki Ogawa, Masaru Saijo, Yoichi Sato, Kenichiro Sawada, Hiroshi Shibai, Keisuke Shinozaki, Hiroyuki Sugita, Shinsuke Takeuchi, Chihiro Tokoku, Thierry Tirolien, Hideki Uchida
    Proceedings of SPIE - The International Society for Optical Engineering 11443 2020年  
    We present an overview of the cryogenic system of the next-generation infrared observatory mission SPICA. One of the most critical requirements for the SPICA mission is to cool the whole science equipment, including the 2.5 m telescope, to below 8 K to reduce the thermal background and enable unprecedented sensitivity in the mid- and far-infrared region. Another requirement is to cool focal plane instruments to achieve superior sensitivity. We adopt the combination of effective radiative cooling and mechanical cryocoolers to accomplish the thermal requirements for SPICA. The radiative cooling system, which consists of a series of radiative shields, is designed to accommodate the telescope in the vertical configuration. We present thermal model analysis results that comply with the requirements to cool the telescope and focal plane instruments.
  • Keisuke Shinozaki, Yoichi Sato, Chihiro Tokoku, Masaru Saijo, Hiroyuki Ogawa, Takao Nakagawa, Kenichiro Sawada, Hiroyuki Sugita, Tadahito Mizutani, Hideo Matsuhara, Shoji Tsunematsu, Seiji Yoshida, Kenichi Kanao, Akinobu Okabayashi, Katsuhiro Narasaki, Hiroshi Shibai
    Proceedings of SPIE - The International Society for Optical Engineering 11443 2020年  
    The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is to be launched into orbit around the second Lagrangian point (L2) in the Sun-Earth system. Taking advantage of the thermal environment in L2, a 2.5m-class large IR telescope is cooled below 8K in combination with effective radiant cooling and a mechanical cooling system. SPICA adopts a cryogen-free system to prevent the mission operation lifetime being limited by the amount of cryogen as a refrigerant. Currently, the mechanical cooler system with the feasible solution giving a proper margin is proposed. As a baseline design, 4K / 1K-class Joule-Thomson coolers are used to cool the telescope and thermal interface for Focal Plane Instruments (FPIs). Additionally, two sets of double stage stirling coolers (2STs) are used to cool the telescope shield. In this design, nominal operation of FPIs can be kept when one mechanical cooler is in failure. In this paper, current baseline configuration of the mechanical cooler system and current status of mechanical coolers developments which need to satisfy the specific requirements of SPICA cryogenic system are presented.
  • Julien Archer, Dominic Doyle, Joel Boyadjian, Lucas Courcoult Mifsud, Anouck Paoletti, Rémi Pujol, Didier Castel, Stéphane Iugovich, Thierry Blais, Jan Tauber, Jacques Rouquet, Hideo Matsuhara, Hidehiro Kaneda, Takao Nakagawa
    Proceedings of SPIE - The International Society for Optical Engineering 11443 2020年  
    The ESA/JAXA SPICA mission is a candidate for the ESA Cosmic Vision Medium Class M5 opportunity. Since 2019 an Airbus Defence and Space team has been performing a trade-off study (on behalf of ESA) to establish a baseline telescope optical configuration and design, which can meet the mission scientific performance requirements. This paper describes the telescope baseline design selected, with first estimates of the expected optical performance. The optical design wavelength is 20 microns for an operating temperature of 8 K covering a total bandwidth of 12 to 420 microns over a 30 arc minutes field of view, with a total required collecting area of at least 4.0 m2;. The fundamental mission science driver is to achieve a sky background (astrophysical sources) limited performance. The telescope is designed to illuminate three instruments namely; SMI (JAXA - Japan), SAFARI (SRON - Netherlands) and B-BOP (CEA - France).
  • Hiroshi Maeshima, Kosei Matsumoto, Yasuhiro Hirahara, Takao Nakagawa, Takehiko Wada, Koichi Nagase, Shinki Oyabu, Toyoaki Suzuki, Takuma Kokusho, Hidehiro Kaneda, Ryota Ito, Daichi Ishikawa
    Proceedings of SPIE - The International Society for Optical Engineering 11451 2020年  
    We measured the transmittance of low-resistivity (∼10 2 ωcm) and high-resistivity (> 10 10 ωcm) CdZnTe, which are candidates for Immersion grating (IG) in 10-18μm wavelength, at cryogenic temperature. IG is a compact diffraction grating and we are developing a cryogenically operated 10-18μm IG for SMI/HR (SPICA Mid-Infrared Instrument / High-Resolution spectrometer) of SPICA (SPace Infrared telescope for Cosmology and Astrophysics) We performed two experiments: Transmittance measurement with a convergent light Fourier transform spectrometer, and with a collimated lamp beam system. Our result shows that the low-resistivity CdZnTe has large absorption (> 0.5 cm {-1}) and the high-resistivity CdZnTe has low absorption (< 0.1 cm {-1}) at 8.5K at 10-18 μm. The high-resistivity CdZnTe is promising as an IG material although higher precision measurement is needed to determine whether it meets the absorption coefficient requirement (< 0.01 cm {-1}) at cryogenic temperature.
  • Satoshi Mayama, Sebastián Pérez, Nobuhiko Kusakabe, Takayuki Muto, Takashi Tsukagoshi, Michael L. Sitko, Michihiro Takami, Jun Hashimoto, Ruobing Dong, Jungmi Kwon, Saeko S. Hayashi, Tomoyuki Kudo, Masayuki Kuzuhara, Katherine Follette, Misato Fukagawa, Munetake Momose, Daehyeon Oh, Jerome De Leon, Eiji Akiyama, John P. Wisniewski, Yi Yang, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Michael Bonnefoy, Joseph C. Carson, Jeffrey Chilcote, Thayne Currie, Markus Feldt, Miwa Goto, Carol A. Grady, Tyler Groff, Olivier Guyon, Yutaka Hayano, Masahiko Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Nemanja Jovanovic, Ryo Kandori, Jeremy Kasdin, Gillian R. Knapp, Julien Lozi, Frantz Martinache, Taro Matsuo, Michael W. McElwain, Shoken Miyama, Jun Ichi Morino, Amaya Moro-Martin, Takao Nakagawa, Tetsuo Nishimura, Tae Soo Pyo, Evan A. Rich, Eugene Serabyn, Hiroshi Suto, Ryuji Suzuki, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda, Taichi Uyama, Motohide Tamura
    Astronomical Journal 159(1) 2020年1月  
    The SR 24 multistar system hosts both circumprimary and circumsecondary disks, which are strongly misaligned with each other. The circumsecondary disk is circumbinary in nature. Interestingly, both disks are interacting, and they possibly rotate in opposite directions. To investigate the nature of this unique twin disk system, we present 0.″1 resolution near-infrared polarized intensity images of the circumstellar structures around SR 24, obtained with HiCIAO mounted on the Subaru 8.2 m telescope. Both the circumprimary disk and the circumsecondary disk are resolved and have elongated features. While the position angle of the major axis and radius of the near-IR (NIR) polarization disk around SR 24S are 55° and 137 au, respectively, those around SR 24N are 110° and 34 au, respectively. With regard to overall morphology, the circumprimary disk around SR 24S shows strong asymmetry, whereas the circumsecondary disk around SR 24N shows relatively strong symmetry. Our NIR observations confirm the previous claim that the circumprimary and circumsecondary disks are misaligned from each other. Both the circumprimary and circumsecondary disks show similar structures in CO observations in terms of its size and elongation direction. This consistency is because both NIR and CO are tracing surface layers of the flared disks. As the radius of the polarization disk around SR 24N is roughly consistent with the size of the outer Roche lobe, it is natural to interpret the polarization disk around SR 24N as a circumbinary disk surrounding the SR 24Nb-Nc system. 12 12
  • Koji Yamamoto, Takao Nakagawa, Shogo Tokui, Kazuki Munakata
    Proceedings of the International Conference on Software Engineering and Knowledge Engineering, SEKE PartF162440 342-346 2020年  
    © 2020 Knowledge Systems Institute Graduate School. All rights reserved. Necessary and sufficient combinatorial testing is important especially for continuous development to provide stateful service APIs that are invoked by an unspecified number of users. Listing API call sequences for this type of test cases is an important factor in achieving both high test coverage and short time required for test execution. This paper proposes a method to list fewer call sequences without reducing API coverage, and a method to measure the degree of adequacy of an API sequence for testing. Evaluations of more than 400 services show that the listing method reduces the number of sequences for half of the services, and that the measurement method can determine whether the reduction is possible or not for each service with high probability.
  • Takao Nakagawa, Kazuki Munakata, Koji Yamamoto
    Proceedings - 2019 IEEE 30th International Symposium on Software Reliability Engineering Workshops, ISSREW 2019 1-6 2019年10月  
    © 2019 IEEE. Regression testing plays an important role in maintaining the quality of web applications as they are modified. To reduce the cost of this testing, researchers have proposed a variety of regression test selection (RTS) techniques. The challenges in applying RTS include the lack of tool implementations and the lack of many application requirements such as automated testing and sufficient documentation. This paper presents the challenges and solutions of applying a simple and safe RTS approach to manual E2E testing of legacy web applications, and presents a case study where it is applied to two development projects. Case study results show that this approach can reduce testing more precisely than a test reduction approach based on developer experience with sufficiently low deployment and labor costs.
  • K. Shinozaki, C. Tokoku, R. Yamamoto, Y. Minami, N. Y. Yamasaki, K. Mitsuda, T. Nakagawa, J. M. Duval, T. Prouvé, I. Charles, M. Lé Du, J. Andre, C. Daniel, M. Linder, S. Tsunematsu, K. Kanao, K. Otsuka, K. Narasaki
    IOP Conference Series: Materials Science and Engineering 502(1) 2019年6月3日  
    The cooler system for the ESA X-ray astronomical mission ATHENA X-IFU instrument is being studied, and a demonstration cooling test has been performed by integrating the mechanical coolers (double-stage Stirling cooler = 2ST, 4K-class and 1K-class Joule Thomson coolers = 4K-JT and 2K-JT) provided by JAXA with the coolers (15K-class pulse tube cooler = PT15K and 50mK hybrid cooler) provided by CEA into the cryostat. This paper describes the measured cooling performances of these Joule Thomson coolers under successful integration with the 50mK hybrid cooler and the pulse tube cooler. The demonstration test is proceeded under the international framework of ESA Core Technology Program (CTP) for a detector cooling system demonstration for ATHENA, and should provide valuable insight for other future space missions such as SPICA and LiteBIRD. &copy; Published under licence by IOP Publishing Ltd.
  • Tomotsugu Goto, Nagisa Oi, Yousuke Utsumi, Rieko Momose, Hideo Matsuhara, Tetsuya Hashimoto, Yoshiki Toba, Youichi Ohyama, Toshinobu Takagi, Chia Ying Chiang, Seong Jin Kim, Ece Kilerci Eser, Matthew Malkan, Helen Kim, Takamitsu Miyaji, Myungshin Im, Takao Nakagawa, Woong Seob Jeong, Chris Pearson, Laia Barrufet, Chris Sedgwick, Denis Burgarella, Veronique Buat, Hiroyuki Ikeda
    Publications of the Astronomical Society of Japan 71(2) 2019年4月  
    Much of star formation is obscured by dust. For a complete understanding of the cosmic star formation history (CSFH), infrared (IR) census is indispensable. AKARI carried out deep mid-infrared observations using its continuous nine-band filters in the North Ecliptic Pole (NEP) field (5.4 deg2). This took a significant amount of the satellite's lifetime, ∼10% of the entire pointed observations. By combining archival Spitzer (five bands) and WISE (four bands) mid-IR photometry, we have, in total, 18-band mid-IR photometry, which is the most comprehensive photometric coverage in the mid-IR for thousands of galaxies. However, we only had shallow optical imaging (∼25.9AB magnitude) in a small area, 1.0 deg2. As a result, thousands of AKARI's infrared sources remained undetected in the optical. Using the new Hyper Suprime-Cam on the Subaru telescope, we obtained deep enough optical images of the entire AKARI NEP field in five broad bands (g ∼ 27.5mag). These provided photometric redshift, and thereby IR luminosity, for the previously undetected faint AKARI IR sources. Combined with the accurate mid-IR luminosity measurement, we constructed mid-IR luminosity functions (LFs), and thereby performed a census of dust-obscured CSFH in the entire AKARI NEP field. We have measured restframe μm and 12μm LFs, and estimated total infrared LFs at 0.35 < z < 2.2. Our results are consistent with our previous work, but with much reduced statistical errors thanks to the large-area coverage of the new data. We have possibly witnessed the turnover of CSFH at z ∼ 2.
  • Evan A. Rich, John P. Wisniewski, Thayne Currie, Misato Fukagawa, Carol A. Grady, Michael L. Sitko, Monika Pikhartova, Jun Hashimoto, Lyu Abe, Wolfgang Brandner, Timothy D. Brandt, Joseph C. Carson, Jeffrey Chilcote, Ruobing Dong, Markus Feldt, Miwa Goto, Tyler Groff, Olivier Guyon, Yutaka Hayano, Masahiko Hayashi, Saeko S. Hayashi, Thomas Henning, Klaus W. Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Nemanja Jovanovic, Ryo Kandori, Jeremy Kasdin, Gillian R. Knapp, Tomoyuki Kudo, Nobuhiko Kusakabe, Masayuki Kuzuhara, Jungmi Kwon, Julien Lozi, Frantz Martinache, Taro Matsuo, Satoshi Mayama, Michael W. Mcelwain, Shoken Miyama, Jun Ichi Morino, Amaya Moro-Martin, Takao Nakagawa, Tetsuo Nishimura, Tae Soo Pyo, Eugene Serabyn, Hiroshi Suto, Ray W. Russel, Ryuji Suzuki, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Edwin L. Turner, Taichi Uyama, Kevin R. Wagner, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda, Motohide Tamura
    Astrophysical Journal 875(1) 2019年4月  
    We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instruments at Subaru Observatory. The polarimetric imagery resolve a broken ring structure surrounding HD 163296 that peaks at a distance along the major axis of 0.″65 (66 au) and extends out to 0.″98 (100 au) along the major axis. Our 2011 H-band data exhibit clear axisymmetry, with the NW and SE side of the disk exhibiting similar intensities. Our data are clearly different from 2016 epoch H-band observations of the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), which found a strong 2.7× asymmetry between the NW and SE side of the disk. Collectively, these results indicate the presence of time-variable, non-azimuthally symmetric illumination of the outer disk. While our SCExAO/CHARIS data are sensitive enough to recover the planet candidate identified from NIRC2 in the thermal infrared (IR), we fail to detect an object with JHK brightness nominally consistent with this object. This suggests that the candidate is either fainter in JHK bands than model predictions, possibly due to extinction from the disk or atmospheric dust/clouds, or that it is an artifact of the data set/data processing, such as a residual speckle or partially subtracted disk feature. Assuming standard hot-start evolutionary models and a system age of 5 Myr, we set new, direct mass limits for the inner (outer) Atacama Large Millimeter/submillimeter Array (ALMA)-predicted protoplanet candidate along the major (minor) disk axis of of 1.5 (2) M . J
  • Shuhei Koyama, Yusei Koyama, Takuji Yamashita, Masao Hayashi, Hideo Matsuhara, Takao Nakagawa, Shigeru V. Namiki, Tomoko L. Suzuki, Nao Fukagawa, Tadayuki Kodama, Lihwai Lin, Kana Morokuma-Matsui, Rhythm Shimakawa, Ichi Tanaka
    Astrophysical Journal 874(2) 2019年4月  
    Recent simulations predict that the presence of the stellar bulge suppress the efficiency of star formation (SF) in early-type galaxies, and this "morphological quenching" scenario is supported by many observations. In this study, we discuss the net effect of galaxy morphologies on the star formation efficiency (SFE) during the phase of galaxy transition, on the basis of our CO(J = 1 - 0) observations of 28 local "green valley" galaxies with the Nobeyama 45 m Radio Telescope. We observed 13 disk-dominated and 15 bulge-dominated green valley galaxies at fixed stellar mass (M ) and star formation rate (SFR), supplemented by 1 disk- and 6 bulge-dominated galaxies satisfying the same criteria from the xCOLD GASS survey. By using a total of 35 green valley galaxies, we reveal that the distributions of molecular gas mass, molecular gas fraction, and SFE of green valley galaxies do not change with their morphologies, suggesting little impact of galaxy morphologies on their SFE, and interestingly, this result is also valid for normal star-forming galaxies on the SF main sequence selected from the xCOLD GASS galaxies. On the other hand, we find that ∼20% of the bulge-dominated green valley galaxies do not show significant CO emission line, showing high SFEs for their M and SFR. These molecular gas deficient sources that are identified only in the bulge-dominated green valley galaxies may represent an important population during the quenching phase under the influence of the stellar bulge, but our results suggest that the presence of the stellar bulge does not decrease the efficiency of ongoing SF, in contrast to the prediction of the morphological quenching scenario. ∗ ∗
  • Ryosuke Doi, Takao Nakagawa, Naoki Isobe, Shunsuke Baba, Kenichi Yano, Mitsuyoshi Yamagishi
    Publications of the Astronomical Society of Japan 71(2) 2019年4月  
    We present a systematic study of the 3.0μm H O ice and the 3.4μm aliphatic carbon absorption features toward 48 local ultraluminous infrared galaxies (ULIRGs) using spectra obtained by the AKARI Infrared Camera to investigate the UV environment in their star-forming regions. All the ULIRGs in our sample exhibit a ratio of optical depth of H O ice to silicate dust (τ /τ ) that is lower than that in the Taurus dark cloud. This implies that ULIRGs cannot be described as an ensemble of low-mass star-forming regions and that a significant amount of high-mass star-forming regions contribute to star-forming clouds in local ULIRGs. The results also show that the ratios of optical depth of aliphatic carbon to silicate dust, τ /τ , exhibit diverse values. We investigate two effects that can affect this ratio: the geometric temperature gradient (which increases the ratio) and the intense UV environment (which decreases it). The geometric temperature gradient is typically considered as a sign of active galactic nuclei (AGN). ULIRGs with AGN signs (optical classification, near-infrared color, and a polycyclic aromatic hydrocarbon emission strength of 3.3μm) indeed tend to exhibit a large τ /τ ratio. However, we find that the presence of buried AGN is not the only cause of the geometric temperature gradient, because the enhancement of the ratio is also evident in pure starburst-like ULIRGs without these AGN signs. Regarding the intense UV environment in star-forming regions, the correlation between the aliphatic carbon ratio and the ratio of the [C ] 158μm line luminosity to the far-infrared luminosity (L /L ), which represents the UV environment in photodissociation regions, implies that the intense UV environment causes the decrease of the aliphatic carbon ratio. We find that an intense UV environment (G/n > 3) in star-forming regions is needed for the aliphatic carbon ratio to be suppressed. 2 2 3.0 9.7 3.4 9.7 3.4 9.7 II [C II] FIR H
  • Ruben Asensio-Torres, Thayne Currie, Markus Janson, Silvano Desidera, Masayuki Kuzuhara, Klaus Hodapp, Timothy D. Brandt, Olivier Guyon, Julien Lozi, Tyler Groff, Jeremy Kasdin, Jeffrey Chilcote, Nemanja Jovanovic, Frantz Martinache, Michael Sitko, Eugene Serabyn, Kevin Wagner, Eiji Akiyama, Jungmi Kwon, Taichi Uyama, Yi Yang, Takao Nakagawa, Masahiko Hayashi, Michael McElwain, Tomoyuki Kudo, Thomas Henning, Motohide Tamura
    Astronomy and Astrophysics 622 2019年2月1日  
    We present SCExAO/CHARIS 1.1-2.4 μm integral field direct spectroscopy of the young HIP 79124 triple system. HIP 79124 is a member of the Scorpius-Centaurus association, consisting of an A0V primary with two low-mass companions at a projected separation of < 1″. Thanks to the high quality wavefront corrections provided by SCExAO, both companions are decisively detected without the employment of any PSF-subtraction algorithm to eliminate quasi-static noise. The spectrum of the outer C object is very well matched by Upper Scorpius M4 ± 0.5 standard spectra, with a T = 2945 ± 100 K and a mass of ∼350 M . HIP 79124 B is detected at a separation of only 180 mas in a highly-correlated noise regime, and it falls in the spectral range M6 ± 0.5 with T = 2840 ± 190 K and ∼100 M . Previous studies of stellar populations in Sco-Cen have highlighted a discrepancy in isochronal ages between the lower-mass and higher-mass populations. This could be explained either by an age spread in the region, or by conventional isochronal models failing to reproduce the evolution of low-mass stars. The HIP 79124 system should be coeval, and therefore it provides an ideal laboratory to test these scenarios. We place the three components in a color-magnitude diagram and find that the models predict a younger age for the two low-mass companions (∼3 Myr) than for the primary star (∼6 Myr). These results imply that the omission of magnetic effects in conventional isochronal models inhibit them from reproducing early low-mass stellar evolution, which is further supported by the fact that new models that include such effects provide more consistent ages in the HIP 79124 system. eff Jup eff Jup
  • Felix Aharonian, Hiroki Akamatsu, Fumie Akimoto, Steven W. Allen, Lorella Angelini, Marc Audard, Hisamitsu Awaki, Magnus Axelsson, Aya Bamba, Marshall W. Bautz, Roger Blandford, Laura W. Brenneman, Gregory V. Brown, Esra Bulbul, Edward M. Cackett, Maria Chernyakova, Meng P. Chiao, Paolo S. Coppi, Elisa Costantini, Jelle De Plaa, Cor P. De Vries, Jan Willem Den Herder, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan E. Eckart, Teruaki Enoto, Yuichiro Ezoe, Andrew C. Fabian, Carlo Ferrigno, Adam R. Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi C. Gallo, Poshak Gandhi, Margherita Giustini, Andrea Goldwurm, Liyi Gu, Matteo Guainazzi, Yoshito Haba, Kouichi Hagino, Kenji Hamaguchi, Ilana M. Harrus, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Kiyoshi Hayashida, Junko S. Hiraga, Ann Hornschemeier, Akio Hoshino, John P. Hughes, Yuto Ichinohe, Ryo Iizuka, Hajime Inoue, Yoshiyuki Inoue, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Masachika Iwai, Jelle Kaastra, Tim Kallman, Tsuneyoshi Kamae, Jun Kataoka, Satoru Katsuda, Nobuyuki Kawai, Richard L. Kelley, Caroline A. Kilbourne, Takao Kitaguchi, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Katsuji Koyama, Shu Koyama, Peter Kretschmar, Hans A. Krimm, Aya Kubota, Hideyo Kunieda, Philippe Laurent, Shiu Hang Lee, Maurice A. Leutenegger, Olivier Limousin, Michael Loewenstein, Knox S. Long, David Lumb, Greg Madejski, Yoshitomo Maeda, Daniel Maier, Kazuo Makishima, Maxim Markevitch, Hironori Matsumoto, Kyoko Matsushita, Dan McCammon, Brian R. McNamara, Missagh Mehdipour, Eric D. Miller, Jon M. Miller, Shin Mineshige
    Publications of the Astronomical Society of Japan 70(6) 2018年12月1日  
    We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray/gamma-ray sources on the sky, and the only source from which polarized X-ray photons have been detected. SGD observed the Crab nebula during the initial test observation phase of Hitomi. We performed data analysis of the SGD observation, SGD background estimation, and SGD Monte Carlo simulations and successfully detected polarized gamma-ray emission from the Crab nebula with only about 5 ks exposure time. The obtained polarization fraction of the phase-integrated Crab emission (sum of pulsar and nebula emissions) is (22.1%±10.6%), and the polarization angle is 110°.7 + 13°.2/-13°.0 in the energy range of 60.160 keV (the errors correspond to the 1 σ deviation). The confidence level of the polarization detection was 99.3%. The polarization angle measured by SGD is about one sigma deviation with the projected spin axis of the pulsar, 124°.0 ± 0°.0.1.
  • Ji Hoon Kim, Myungshin Im, Dohyeong Kim, Jong Hak Woo, Marios Karouzos, Hyung Mok Lee, Myung Gyoon Lee, Hyunsung D. Jun, Takao Nakagawa, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Toshinobu Takagi, Youichi Ohyama
    Publications of the Astronomical Society of Japan 70(6) 2018年12月1日  
    We investigate the connection between active galactic nucleus (AGN) and star formation activities of AGN host galaxies by studying the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature of 79 type 1 AGNs using the AKARI space telescope. Utilizing the slitless spectroscopic capability of the AKARI Infrared Camera, we obtained the spectra in the wavelength range of 2–5 μm from extended regions of the sample galaxies in order to measure star formation activity from the entire host galaxies. We detected the 3.3 μm PAH emission feature from 18 sample galaxies and measured the luminosities of the feature (L ). We found that L is significantly correlated with AGN luminosities (L ), such as 5100 Å monochromatic luminosity, and X-ray luminosity regardless of host galaxy morphology and radio-loudness. The correlation between L and L follows L ∝ L . Therefore we suggest that host galaxies with stronger AGN activities have stronger star formation activities. We also found that the ratios between L and the bolometric infrared luminosity (L ) of our sample galaxies are lower than for non-AGN galaxies due to increased L . We suggest that this can be attributed to the contribution of AGN to L PAH3.3 PAH3.3 AGN PAH3.3 AGN PAH3.3 AGN PAH3.3 IR IR IR 0 9

MISC

 675
  • 中川俊輔, 佐野圭, CORDOVA-ALARCON Jose Rodrigo, HUGO Schuls Victor, 中山大輔, ROSALES Reynel Josue Galindo, 増井博一, AREDA Eyoas Ergetu, CHATAR Keenan Alexsei Aamir, EZRA Fielding, 大谷將壽, 林田健太郎, 宮川大樹, 川崎悠貴, BASTIEN Morelle Bernard Andre, 唐木翔平, 佐藤凛, SHRESTHA Hari R., NARONGPHUN Chinathip, OERGER Necmi Cihan, HUSSEINAT Etti-Balogun Oluwatofunmi, ROSA Marco, 田中一晃, 鶴本航平, DAVID Dai, 中川貴雄, 松原英雄, 宮崎康行, 平子敬一, 船瀬龍, 榎木谷海, 田中颯, 五十里哲, 軸屋一郎, 谷津陽一
    日本天文学会年会講演予稿集 2024 2024年  
  • 佐野, 圭, 趙, 孟佑, 北村, 健太郎, 寺本, 万里子, 増井, 博一, 布施, 哲人, 瀧本, 幸司, ORGER, Necmi, CORODOVA-Alagon, Jose Rodrigo, SCHULZ, Victor Hugo, AMPADU, Ofosu Joseph, 中川, 貴雄, 宮崎, 康行, 松原, 英雄, 和田, 武彦, 磯部, 直樹, 船瀬, 龍, 津村, 耕司, 松浦, 周二, 高橋, 葵, 五十里, 哲, 谷津, 陽一, 軸屋, 一郎, 青柳, 賢英
    第23回宇宙科学シンポジウム 講演集 2023年1月  
    レポート番号: S2-004
  • 瀧本幸司, 佐野圭, 當銘優斗, 川崎悠貴, 中川俊輔, AREDA Eyoas Ergetu, FIELDING Ezra, CHATAR Keenan Alexsei Aamir, 松浦周二, 廣瀬優樹, 小鹿哲雅, 津本明音, 津村耕司, 中川貴雄, 松原英雄, 磯部直樹, 榎木谷海, 田中颯, 高橋葵
    日本天文学会年会講演予稿集 2023 2023年  
  • 佐野圭, 趙孟佑, 北村健太郎, 寺本万里子, 増井博一, 布施哲人, 瀧本幸司, 山内貴志, 中山大輔, OERGER Necmi Cihan, CORDOVA-ALARCON Jose Rodrigo, SCHULZ Victor Hugo, OFOSU Joseph, 中川貴雄, 松原英雄, 磯部直樹, 宮崎康行, 平子敬一, 船瀬龍, 松浦周二, 和田武彦, 津村耕司, 高橋葵, 五十里哲, 谷津陽一, 軸屋一郎, 青柳賢英
    日本天文学会年会講演予稿集 2023 2023年  
  • 瀧本幸司, 佐野圭, 松浦周二, 津村耕司, 中川貴雄, 松原英雄, 磯部直樹, 和田武彦, 高橋葵, 布施哲人, 趙孟佑, 北村健太郎, 増井博一, 寺本万里子, NECMI Oerger, RODRIGO Cordova-Alarcon Jose, VICTOR Schulz, JOSEPH Ofosu, 宮崎康行, 船瀬龍, 五十里哲, 青柳賢英, 谷津陽一, 軸屋一郎
    日本天文学会年会講演予稿集 2023 2023年  

共同研究・競争的資金等の研究課題

 49

● 専任大学名

 1
  • 専任大学名
    東京大学(University of Tokyo)