研究者業績
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
研究キーワード
5研究分野
1委員歴
3-
2014年4月 - 現在
-
2011年9月 - 現在
-
2006年 - 2009年
受賞
2論文
382-
Astronomy & Astrophysics 2023年10月
-
The Astrophysical Journal 2023年8月1日
-
The Astrophysical Journal 2023年7月1日
-
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.
-
The Astronomical Journal 2023年2月1日
MISC
674-
Astronomy and Astrophysics 543 2012年Aims. We investigate the properties of interstellar dust in the Galactic center region toward the Arches and Quintuplet clusters. Methods. With the Fourier Transform Spectrometer of the AKARI/Far-Infrared Surveyor, we performed the far-infrared (60-140 cm ) spectral mapping of an area of about 10′ × 10′ that includes both clusters to obtain a low-resolution (R = 1.2 cm ) spectrum at every spatial bin of 30′′ × 30′′. Results. We derive the spatial variations in the dust continuum emission at different wavenumbers, which are compared with those of the [OIII] 88 μm (113 cm ) emission and the OH 119 μm (84 cm ) absorption. The spectral fitting shows that two modified blackbody components with temperatures of ∼20 K and ∼50 K can reproduce most of the continuum spectra. For some spectra, however, we find that there is a significant excess on top of a modified blackbody continuum around 80-90 cm (110-130 μm). Conclusions. The warmer dust component is spatially correlated with the [OIII] emission and hence likely to be associated with the highly-ionized gas locally heated by intense radiation from the two clusters. The excess emission probably represents a dust feature, which is found to be spatially correlated with the OH absorption and a CO cloud. We find that a dust model including micron-sized graphite grains can quite closely reproduce the observed spectrum with the dust feature. © 2012 ESO. -1 -1 -1 -1 -1
-
Astronomy and Astrophysics 548 2012年We present a photometric catalog of infrared (IR) sources based on the North Ecliptic Pole Wide field (NEP-Wide) survey of AKARI, which is an infrared space telescope launched by Japan. The NEP-Wide survey covered 5.4 deg area, a nearly circular shape centered on the NEP, using nine photometric filter-bands from 2-25 μm of the Infrared Camera (IRC). Extensive efforts were made to reduce possible false objects due to cosmic ray hits, multiplexer bleeding phenomena around bright sources, and other artifacts. The number of detected sources varied depending on the filter band: with about 109 000 sources being cataloged in the near-infrared (NIR) bands at 2-5 μm, about 20 000 sources in the shorter parts of the mid-infrard (MIR) bands between 7-11 μm, and about 16 000 sources in the longer parts of the MIR band, with ∼4000 sources at 24 μm. The estimated 5σ detection limits are approximately 21 mag (mag) in the 2-5 μm bands, 19.5-19 mag in the 7-11 μm, and 18.8-18.5 mag in the 15-24 μm bands in the AB magnitude scale. The completenesses for those bands were evaluated as a function of magnitude: the 50% completeness limits are about 19.8 mag at 3 μm, 18.6 mag at 9 μm, and 18 mag at 18 μm band, respectively. To construct a reliable source catalog, all of the detected sources were examined by matching them with those in other wavelength data, including optical and ground-based NIR bands. The final band-merged catalog contains about 114 800 sources detected in the IRC filter bands. The properties of the sources are presented in terms of the distributions in various color-color diagrams. © ESO 2012. 2
-
Proceedings of SPIE - The International Society for Optical Engineering 8442 2012年We present the overview and the current status of SPICA (Space Infrared Telescope for Cosmology and Astrophysics), which is a mission optimized for mid- and far-infrared astronomy with a cryogenically cooled 3.2 m telescope. SPICA has high spatial resolution and unprecedented sensitivity in the mid- and far-infrared, which will enable us to address a number of key problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets. To reduce the mass of the whole mission, SPICA will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, a combination of which allows us to have a 3-m class cooled (6 K) telescope in space with moderate total weight (3.7t). SPICA is proposed as a Japanese-led mission together with extensive international collaboration. ESA's contribution to SPICA has been studied under the framework of the ESA Cosmic Vision. The consortium led by SRON is in charge of a key focal plane instrument SAFARI (SPICA Far-Infrared Instrument). Korea and Taiwan are also important partners for SPICA. US participation to SPICA is under discussion. The SPICA project is now in the "risk mitigation phase". The target launch year of SPICA is 2022. © 2012 SPIE.
-
Advances in Space Research 47(9) 1455-1462 2011年5月3日The SPICA coronagraph instrument (SCI) provides high-contrast imaging and moderate resolution (R < 200) spectroscopy at the wavelength range from 3.5 to 27 μm. Based on the planet evolutional model calculated by Burrows et al. (2003), SCI will search for gas giant planets down to one Jupiter mass around nearby young (1 Gyr) stars and two Jupiter masses around nearby old (5 Gyr) stars. SCI also allows to characterizing those planets of less than 1 Gyr by spectroscopic observations to reveal the nature of planetary formation and evolution. Focusing on the high sensitivity and high contrast at wavelengths longer than 10 μm, we show that SCI also allows us to directly image icy giant planets like Uranus and Neptune as well as gas giant planets around nearby early-type stars. In this paper, we compare the capabilities of SCI and the JWST coronagraphs and also discuss a new approach to answering questions concerning the formation and evolution of planetary systems through planet detection with SCI. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.
-
Publications of the Astronomical Society of Japan 62(5) 1155-1166 2010年10月25日The Far-Infrared Surveyor (FIS) onboard the AKARI satellite has a spectroscopic capability provided by a Fourier transform spectrometer (FIS-FTS). FIS-FTS is the first space-borne imaging FTS dedicated to far-infrared astronomical observations. We describe the calibration process of the FIS-FTS, and discuss its accuracy and reliability. The calibration is based on observational data of bright astronomical sources as well as two instrumental sources. We have compared the FIS-FTS spectra with the spectra obtained from the LongWavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO), having a similar spectral coverage. The present calibration method accurately reproduces the spectra of several solar system objects having a reliable spectral model. Under this condition the relative uncertainty of the calibration of the continuum is estimated to be ±?15% for SW, ±10% for 70- 85 cm of LW, and ?20% for 60-70cm of LW; and the absolute uncertainty is estimated to be +35%/-55% for SW, +35%/-55% for 70-85cm of LW, and +40%/-60% for 60-70cm of LW. These values have been confirmed by comparisons with theoretical models and previous observations by the ISO/ LWS. © 2010. Astronomical Society of Japan. -1 -1 -1 -1
-
Astrophysical Journal 721(2) 1233-1261 2010年10月1日We present the results of our systematic infrared 2.5-5μm spectroscopy of 60 luminous infrared galaxies (LIRGs) with infrared luminosities L = 10 -10 L and 54 ultraluminous infrared galaxies (ULIRGs) with L ≥ 10 L , using the AKARI Infrared Camera (IRC). AKARI IRC slit-less spectroscopy allows us to probe the full range of emission from these galaxies, including spatially extended components. The 3.3μm polycyclic aromatic hydrocarbon (PAH) emission features, hydrogen recombination emission lines, and various absorption features are detected and used to investigate the properties of these galaxies. Because of the relatively small effect of dust extinction in the infrared range, quantitative discussion of these dusty galaxy populations is possible. For sources with clearly detectable Brβ (2.63μm) and Brα (4.05μm) emission lines, the flux ratios are found to be similar to those predicted by case B theory. Starburst luminosities are estimated from both 3.3μm PAH and Brα emission, which roughly agree with each other. In addition to the detected starburst activity, a significant fraction of the observed sources display signatures of obscured active galactic nuclei (AGNs), such as low PAH equivalent widths, large optical depths of dust absorption features, and red continuum emission. The energetic importance of optically elusive buried AGNs in optically non-Seyfert galaxies tends to increase with increasing galaxy infrared luminosity, from LIRGs to ULIRGs. © 2010. The American Astronomical Society. All rights reserved. IR ⊙ IR ⊙ 11 12 12
-
Astronomy and Astrophysics 517(7) 2010年8月4日Aims. The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ∼1.7 degree field coinciding with the AKARI north ecliptic pole deep field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives. Methods. The survey consisted of 10 pointings, mosaiced with enough overlap to maintain a similar sensitivity across the central region that reached as low as 21 μJy beam at 1.4 GHz. Results. A catalogue containing 462 sources detected with a resolution of 17.0 × 15.5 is presented. The differential source counts calculated from the WSRT data have been compared with those from the shallow VLA-NEP survey of Kollgaard et al. 1994, and show a pronounced excess for sources fainter than ∼1 mJy, consistent with the presence of a population of star forming galaxies at sub-mJy flux levels. Conclusions. The AKARI north ecliptic pole deep field is the focus of a major observing campaign conducted across the entire spectral region. The combination of these data sets, along with the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the clustering environment of radio galaxies, the nature of obscured radio-loud active galactic nuclei, and the radio/far-infrared correlation for distant galaxies. This catalogue provides the basic data set for a future series of paper dealing with source identifications, morphologies, and the associated properties of the identified radio sources. © 2010 ESO. 2 -1 " "
-
宇宙航空研究開発機構特別資料: = JAXA Special Publication: The Energetic Cosmos; from Suzaku to ASTRO-H (9) 334-335 2010年2月26日資料番号: AA0064574130レポート番号: JAXA-SP-09-008E
-
Edited by Vincent Coude du Foresto, Dawn M. Gelino, and Ignasi Ribas. San Francisco : Astronomical Society of the Pacific 284-290 2010年
共同研究・競争的資金等の研究課題
49-
日本学術振興会 科学研究費助成事業 2023年4月 - 2028年3月
-
日本学術振興会 科学研究費助成事業 2023年4月 - 2027年3月
-
日本学術振興会 科学研究費助成事業 2024年4月 - 2027年3月
-
日本学術振興会 科学研究費助成事業 2023年4月 - 2026年3月
-
日本学術振興会 科学研究費助成事業 2023年6月 - 2025年3月
● 専任大学名
1-
専任大学名東京大学（University of Tokyo)
