研究者業績

坪井 昌人

ツボイ マサト  (Masato TSUBOI)

基本情報

所属
明星大学 理工学部 総合理工学科 常勤教授
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 (名誉教授)
学位
理学博士(1988年3月 東京大学)

J-GLOBAL ID
201801015276314608
researchmap会員ID
B000301395

電波天文学者、銀河系中心の研究者


論文

 143
  • Makoto Miyoshi, Yoshiaki Kato, Junichiro Makino, Masato Tsuboi
    The Astrophysical Journal Letters 963 L18 2024年3月1日  査読有り
  • Masato Tsuboi, Yutaka Hasegawa, Go Tabuchi, Yasuhiro Murata, Koji Yuchi, Tomoaki Toda, Takashi Uchimura, Kimihiro Kimura, Takashi Kasuga
    Publications of the Astronomical Society of Japan 75(3) 567-583 2023年4月5日  査読有り筆頭著者
    We built a Ka-band dual-circular-polarization low-noise receiver for the Misasa 54 m parabola antenna in Misasa, Japan. The antenna is designed to be combined with a transmitter and receiver system at the X band (around 8 GHz) and simultaneously with a receiver system at the Ka band. The Ka band is the frequency band around 30 GHz, which is important for deep-space communications and radio astronomy. The receiver comprises some waveguide components including a feed horn, a circular polarizer, and low-noise amplifiers. The components are installed in a vacuum vessel and are cooled to 4 K with a Gifford-McMahon refrigerator, providing low-noise performance. The receiver is capable of simultaneously handling the left- and right-hand circular-polarization (LHCP and RHCP) channels. The receiver-noise temperature was measured to be T-RX similar or equal to 14 K in both the LHCP and RHCP channels. The system-noise temperature, including the antenna loss and atmospheric attenuation at the zenith, was measured to be T-sys = 36-37 K in both the LHCP and RHCP channels on a clear day in September at Misasa. When the receiver is used with the X-band transmitter, the system-noise temperature is maintained at T-sys similar or equal to 42 K in the RHCP channel. The degradation in the system-noise temperature is attributed to a frequency-selective reflector, which divides the signals in the X and Ka bands. There is no contamination from the transmitter to damage the receiver. The receiver has already been in use for deep-space communications and radio-astronomy observations. Our team in the radio-astronomy laboratory of ISAS/JAXA is responsible for the development of the receiver and the measurements of its performance.
  • Florian Peißker, Michal Zajaček, Nadeen B. Sabha, Masato Tsuboi, Jihane Moultaka, Lucas Labadie, Andreas Eckart, Vladimír Karas, Lukas Steiniger, Matthias Subroweit, Anjana Suresh, Maria Melamed, Yann Clénet
    The Astrophysical Journal 944(2) id.231 2023年2月1日  査読有り
  • Masato Tsuboi, Takahiro Tsutsumi, Atsushi Miyazaki, Ryosuke Miyawaki, Makoto Miyoshi
    Publications of the Astronomical Society of Japan 74(4) 738-756 2022年5月31日  査読有り筆頭著者
  • Ryosuke Miyawaki, Masato Tsuboi, Kenta Uehara, Atsushi Miyazaki
    Publications of the Astronomical Society of Japan psab056 2021年8月4日  査読有り
    We present the results based on the 2.5 arcsec-resolution observations using Atacama Large Millimeter/submillimeter Array (ALMA) of the Galactic Center Molecular Cloud G-0.02-0.07, or the 50 km/s Molecular Cloud (50MC), in the SO (N_J=2_2-1_1) line and 86-GHz continuum emission, the combination of which is considered to trace "hot molecular core candidates" (HMCCs) appearing in the early stage of massive star formation. In the 86-GHz continuum image, we identified nine dust cores in the central part of the 50MC, in which four famous compact HII regions are located. No new ultra-compact HII regions were found. We also identified 28 HMCCs in the 50MC with the SO line. The overall SO distribution had no clear positional correlation with the identified HII regions. The HMCCs in the 50MC showed a variety of association and non-association with dust and Class-I CH3OH maser emissions. The variety suggests that they are not in a single evolutionary stage or environment. Nevertheless, the masses of the identified HMCCs were found to be well approximated by a single power law of their radii, M_LTE/(M_sun)=5.44 x 10^5 (r/(pc))^2.17 at T_ex = 50-100 K. The derived HMCC masses were larger than those of the molecular cores with the same radii in the 50MC and also than those of the molecular clumps in the Galactic disk. Additional observations are needed to confirm the nature of these HMCCs in the 50MC.

MISC

 315

書籍等出版物

 5

担当経験のある科目(授業)

 8

共同研究・競争的資金等の研究課題

 17

学術貢献活動

 1