Dept. of Space Astronomy and Astrophysics

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

 38
  • 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](3P13P0), 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 ~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 (≳85°), and the beam size must be small (≲1 pc). These results suggest that HCN or HCO+ and [CI] lines are effective for observing pc-scale inflows and outflows, respectively.
  • Shunsuke Baba, Masatoshi Imanishi, Takuma Izumi, Taiki Kawamuro, Dieu D. Nguyen, Takao Nakagawa, Naoki Isobe, Shusuke Onishi, Kosei Matsumoto
    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
    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.
  • Shunsuke Baba, Takao Nakagawa, Fumihiko Usui, Mitsuyoshi Yamagishi, Takashi Onaka
    Publications of the Astronomical Society of Japan 71(1) 2 2019年1月1日  査読有り筆頭著者責任著者
    We present a new calibration for the second-order light contamination in the near-infrared grism spectroscopy with the Infrared Camera aboard AKARI, specifically for the post-cryogenic phase of the satellite (Phase 3). Following our previous work on the cryogenic phase (Phases 1 and 2), the wavelength and spectral response calibrations were revised. Unlike Phases 1 and 2, during Phase 3 the temperature of the instrument was not stable and gradually increased from 40 to 47 K. To assess the effect of the temperature increase, we divided Phase 3 into three sub-phases and performed the calibrations separately. As in Phases 1 and 2, we confirmed that there was contamination due to the wavelength dependence of the refractive index of the grism material in every sub-phase. The wavelength calibration curves for the three sub-phases coincided with each other and did not show any significant temperature dependence. The response decreased with temperature by ∼10% from the beginning to the end of Phase 3. We approximated the temperature dependence of the response at a linear relation and derived a correction factor as a function of temperature. The relative fraction of the second-order light contamination to the first-order light was found to be 25% smaller than that in Phases 1 and 2.
  • Shunsuke Baba, Takao Nakagawa, Naoki Isobe, Mai Shirahata
    The Astrophysical Journal 852(2) 83-83 2018年1月9日  査読有り筆頭著者責任著者
    We performed a systematic analysis of the 4.67 μm CO ro-vibrational absorption band toward nearby active galactic nuclei (AGNs) and analyzed the absorption profiles of 10 nearby galaxies collected from the AKARI and Spitzer spectroscopic observations that show the CO absorption feature by fitting a plane-parallel local thermal equilibrium gas model. We found that CO gas is warm (200–500 K) and has a large column density ($N_\rm{H}\gtrsim 10^{23}\,\mathrm{cm}^{-2}$). The heating of the gas is not explicable by either UV heating or shock heating because these processes cannot represent the large column densities of the warm gas. Instead, X-ray photons from the nuclei, which can produce large columns of warm gas with up to $N_\rm{H}\sim 10^{24}\,\mathrm{cm}^{-2}$, are the most convincing power source. The hydrogen column density estimated from the CO band is smaller than that inferred from X-ray observations. These results indicate that the region probed by the near-infrared CO absorption is in the vicinity of the nuclei and is located outside the X-ray emitting region. Furthermore, the covering factors of nearly unity required by the observed deep absorption profiles suggest that the probed region is close to the continuum source, which can be designated as the inner rim of the obscuring material around the AGN.
  • Shunsuke Baba, Takao Nakagawa, Mai Shirahata, Naoki Isobe, Fumihiko Usui, Youichi Ohyama, Takashi Onaka, Kenichi Yano, Chihiro Kochi
    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
    We perform revised spectral calibrations for the AKARI near-infrared grism to correct quantitatively for the effect of the wavelength-dependent refractive index. The near-infrared grism covering the wavelength range of 2.5–5.0 μm, with a spectral resolving power of 120 at 3.6  μm, is found to be contaminated by second-order light at wavelengths longer than 4.9  μm, which is especially serious for red objects. First, we present the wavelength calibration considering the refractive index of the grism as a function of the wavelength for the first time. We find that the previous solution is positively shifted by up to 0.01  μm compared with the revised wavelengths at 2.5–5.0  μm. In addition, we demonstrate that second-order contamination occurs even with a perfect order-sorting filter owing to the wavelength dependence of the refractive index. Secondly, the spectral responses of the system from the first- and second-order light are simultaneously obtained from two types of standard objects with different colors. The response from the second-order light suggests leakage of the order-sorting filter below 2.5  μm. The relations between the output of the detector and the intensities of the first- and second-order light are formalized by a matrix equation that combines the two orders. The removal of the contaminating second-order light can be achieved by solving the matrix equation. The new calibration extends the available spectral coverage of the grism mode from 4.9  μm up to 5.0  μm. The revision can be used to study spectral features falling in these extended wavelengths, e.g., the carbon monoxide fundamental ro-vibrational absorption within nearby active galactic nuclei.

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

 49

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