宇宙物理学研究系

馬場 俊介

ババ シュンスケ  (Shunsuke BABA)

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 特任助教
学位
博士(理学)(2018年3月 東京大学)

研究者番号
10839244
ORCID ID
 https://orcid.org/0000-0002-9850-6290
J-GLOBAL ID
201801003509712856
Researcher ID
GYQ-9109-2022
researchmap会員ID
B000347073

主要な論文

 34
  • Shunsuke Baba, Keiichi Wada, Takuma Izumi, Yuki Kudoh, Kosei Matsumoto
    The Astrophysical Journal 966(1) 15 2024年5月1日  査読有り筆頭著者責任著者
    Recent submillimeter observations have revealed signs of pc-scale molecular inflow and atomic outflow in the nearest Seyfert 2 galaxy, the Circinus galaxy. To verify the gas kinematics suggested by these observations, we performed molecular and atomic line transfer calculations based on a physics-based 3D radiation-hydrodynamic model, which has been compared with multi-wavelength observations in this paper series. The major axis position-velocity diagram (PVD) of CO(3-2) reproduces the observed faint emission at the systemic velocity, and our calculations confirm that this component originates from failed winds falling back to the disk plane. The minor-axis PVD of [CI]($^3P_1$-$^3P_0$), when created using only the gas with positive radial velocities, presents a sign of blue- and redshifted offset peaks similar to those in the observation, suggesting that the observed peaks indeed originate from the outflow, but that the model may lack outflows as strong as those in the Circinus galaxy. Similar to the observed HCN(3-2), the similar dense gas tracer HCO$^+$(3-2) can exhibit nuclear spectra with inverse P-Cygni profiles with $\sim$0.5 pc beams, but the line shape is azimuthally dependent. The corresponding continuum absorbers are inflowing clumps at 5-10 pc from the center. To detect significant absorption with a high probability, the inclination must be fairly edge-on ($\gtrsim$85$^\circ$), and the beam size must be small ($\lesssim$1 pc). These results suggest that HCN or HCO$^+$ and [CI] lines are effective for observing pc-scale inflows and outflows, respectively.
  • Baba, S., Imanishi, M., Izumi, T., Kawamuro, T., Nguyen, D.D., Nakagawa, T., Isobe, N., Onishi, S., Matsumoto, K.
    The Astrophysical Journal 928(2) 184-184 2022年4月1日  査読有り筆頭著者責任著者
    Abstract The ultraluminous infrared galaxy IRAS 17208−0014 is a late-stage merger that hosts a buried active galactic nucleus (AGN). To investigate its nuclear structure, we performed high-spatial-resolution ( ∼ 0.″04 ∼ 32 pc) Atacama Large Millimeter/submillimeter Array (ALMA) observations in Band 9 (∼450 μm or ∼660 GHz), along with near-infrared AKARI spectroscopy in 2.5–5.0 μm. The Band 9 dust continuum peaks at the AGN location, and toward this position CO(J = 6 − 5) and CS(J = 14 − 13) are detected in absorption. Comparison with nonlocal thermal equilibrium calculations indicates that, within the central beam (r ∼ 20 pc), there exists a concentrated component that is dense (107 cm−3) and warm (>200 K) and has a large column density (${N}_{ { {\rm{H } } }_{2 } }\gt {10}^{23}\,{\mathrm{cm } }^{-2}$). The AKARI spectrum shows deep and broad CO rovibrational absorption at 4.67 μm. Its band profile is well reproduced with a similarly dense and large column but hotter (∼1000 K) gas. The region observed through absorption in the near-infrared is highly likely in the nuclear direction, as in the submillimeter, but with a narrower beam including a region closer to the nucleus. The central component is considered to possess a hot structure where vibrationally excited HCN emission originates. The most plausible heating source for the gas is X-rays from the AGN. The AKARI spectrum does not show other AGN signs in 2.5–4 μm, but this absence may be usual for AGNs buried in a hot mid-infrared core. Further, based on our ALMA observations, we relate the various nuclear structures of IRAS 17208−0014 that have been proposed in the literature.
  • Kenichi Yano, Shunsuke Baba, Takao Nakagawa, Matthew A. Malkan, Naoki Isobe, Mai Shirahata, Ryosuke Doi, Vanshree Bhalotia
    The Astrophysical Journal 922(2) 272-272 2021年12月1日  査読有り責任著者
    Abstract We conducted systematic observations of the H i Brα (4.05 μm) and Brβ (2.63 μm) 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 Brβ/Brα line ratios (∼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 Brβ/Brα line ratios than those observed in Galactic H ii regions. The high Brβ/Brα 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 Brβ/Brα line ratios and show that the observed ratios can be explained by a combination of an optically thick Brα line and an optically thin Brβ line. We simulated the H ii regions in ULIRGs with the Cloudy code, and our results show that the high Brβ/Brα line ratios can be explained by high-density conditions, wherein the Brα line becomes optically thick. To achieve a column density large enough to make the Brα line optically thick within a single H ii region, the gas density must be as high as n ∼ 108 cm−3. We therefore propose an ensemble of H ii regions, in each of which the Brα line is optically thick, to explain the high Brβ/Brα line ratio.
  • Shunsuke Baba, Takao Nakagawa, Fumihiko Usui, Mitsuyoshi Yamagishi, Takashi Onaka
    Publications of the Astronomical Society of Japan 71(1) 2019年1月1日  査読有り筆頭著者責任著者
  • Baba, S., Nakagawa, T., Isobe, N., Shirahata, M.
    Astrophysical Journal 852(2) 83-83 2018年1月9日  査読有り筆頭著者責任著者
  • Baba, S., Nakagawa, T., Shirahata, M., Isobe, N., Usui, F., Ohyama, Y., Onaka, T., Yano, K., Kochi, C.
    Publications of the Astronomical Society of Japan 68(2) 27-27 2016年3月6日  査読有り筆頭著者責任著者

MISC

 1
  • GREX-PLUS Science Team, Akio K. Inoue, Yuichi Harikane, Takashi Moriya, Hideko Nomura, Shunsuke Baba, Yuka Fujii, Naoteru Gouda, Yasuhiro Hirahara, Yui Kawashima, Tadayuki Kodama, Yusei Koyama, Hiroyuki Kurokawa, Taro Matsuo, Yoshiki Matsuoka, Shuji Matsuura, Ken Mawatari, Toru Misawa, Kentaro Nagamine, Kimihiko Nakajima, Shota Notsu, Takafumi Ootsubo, Kazumasa Ohno, Hideo Sagawa, Takashi Shimonishi, Ken-ichi Tadaki, Michihiro Takami, Tsuyoshi Terai, Yoshiki Toba, Takuji Yamashita, Chikako Yasui
    2023年4月17日  
    GREX-PLUS (Galaxy Reionization EXplorer and PLanetary Universe Spectrometer) is a mission candidate for a JAXA's strategic L-class mission to be launched in the 2030s. Its primary sciences are two-fold: galaxy formation and evolution and planetary system formation and evolution. The GREX-PLUS spacecraft will carry a 1.2 m primary mirror aperture telescope cooled down to 50 K. The two science instruments will be onboard: a wide-field camera in the 2-8 $\mu$m wavelength band and a high resolution spectrometer with a wavelength resolution of 30,000 in the 10-18 $\mu$m band. The GREX-PLUS wide-field camera aims to detect the first generation of galaxies at redshift $z>15$. The GREX-PLUS high resolution spectrometer aims to identify the location of the water ``snow line'' in proto-planetary disks. Both instruments will provide unique data sets for a broad range of scientific topics including galaxy mass assembly, origin of supermassive blackholes, infrared background radiation, molecular spectroscopy in the interstellar medium, transit spectroscopy for exoplanet atmosphere, planetary atmosphere in the Solar system, and so on.

書籍等出版物

 1

主要な講演・口頭発表等

 46

所属学協会

 2

共同研究・競争的資金等の研究課題

 2

学術貢献活動

 5

社会貢献活動

 2

メディア報道

 1
  • 株式会社南日本新聞社 南日本新聞 かごしまサイエンスカフェ・ノート 2024年2月16日 新聞・雑誌