2024/04/01 更新

写真a

タカクワ シゲヒサ
高桑 繁久
TAKAKUWA Shigehisa
所属
理工学域理学系 理工学研究科(理学系) 理学専攻 物理・宇宙プログラム 教授
職名
教授
プロフィール
ミリ波、サブミリ波望遠鏡を用いた星、惑星形成の観測的研究
外部リンク

学位

  • 博士(理学) ( 1999年3月   東京大学 )

研究キーワード

  • 天体物理学

  • 電波天文学

  • 星、惑星形成

研究分野

  • 自然科学一般 / 天文学

  • 自然科学一般 / 天文学  / 電波天文学

学歴

  • 東京大学   天文学

    1994年4月 - 1999年3月

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    国名: 日本国

  • 東京大学   天文学科

    1990年4月 - 1994年3月

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    国名: 日本国

経歴

  • 鹿児島大学   理工学域理学系 理工学研究科(理学系) 理学専攻 物理・宇宙プログラム   教授

    2020年4月 - 現在

  • 鹿児島大学   理工学域理学系 理工学研究科(理学系) 物理・宇宙専攻   教授

    2016年3月 - 2020年3月

  • 台湾中央研究院   天文及天文物理研究所   副研究員

    2012年3月 - 2016年2月

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    国名:台湾

  • 台湾中央研究院   天文及天文物理研究所   助研究員

    2007年6月 - 2012年3月

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    国名:台湾

  • 台湾中央研究院   天文及天文物理研究所   助研究天文学家

    2007年5月

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    国名:台湾

  •   ALMA Project Office   Postdoctoral Fellow

    2005年7月 - 2007年5月

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    国名:日本国

  • アメリカ合衆国スミソニアン天文台   SMAプロジェクト   SMAフェロー

    2002年10月 - 2005年6月

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    国名:日本国

  • 台湾中央研究院   天文及天文物理研究所   博士後研究員

    1999年7月 - 2002年9月

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    国名:台湾

  •   Astronomical Data Analysis Center   Postdoctoral Fellow

    1999年4月 - 1999年6月

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    国名:日本国

▼全件表示

所属学協会

  • ALMA望遠鏡CASAユーザーコミット

    2016年9月 - 2021年4月

  • 国立天文台電波専門委員会ミリ波サブミリ波プログラム小委員会

    2016年7月 - 2018年6月

  • 宇宙電波懇談会

    1994年9月 - 現在

  • 日本天文学会

    1994年4月 - 現在

  • 日本天文学会

    1993年4月 - 現在

委員歴

  • 日本アルマ科学諮問委員会   委員  

    2022年10月 - 2024年9月   

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    団体区分:学協会

  • 東アジア・アルマ科学諮問委員会   委員  

    2022年10月 - 2024年9月   

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    団体区分:学協会

  • 宇宙電波懇談会   副委員長  

    2018年4月 - 2022年3月   

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    団体区分:学協会

  • ALMA望遠鏡CASAユーザーコミット   委員  

    2016年9月 - 2021年4月   

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    団体区分:学協会

  • 国立天文台電波専門委員会ミリ波サブミリ波プログラム小委員会   委員長  

    2016年7月 - 2018年6月   

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    団体区分:学協会

 

論文

  • Takakuwa S., Saigo K., Kido M., Ohashi N., Tobin J.J., Jørgensen J.K., Aikawa Y., Aso Y., Gavino S., Han I., Koch P.M., Kwon W., Lee C.W., Lee J.E., Li Z.Y., Lin Z.Y.D., Looney L.W., Mori S., Sai J., Sharma R., Sheehan P.D., Tomida K., Williams J.P., Yamato Y., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). XIV. Flared Dust Distribution and Viscous Accretion Heating of the Disk around R CrA IRS 7B-a .  Astrophysical Journal964 ( 1 )   2024年3月査読 国際共著

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We performed radiative transfer calculations and observing simulations to reproduce the 1.3 mm dust-continuum and C18O (2–1) images in the Class I protostar R CrA IRS7B-a, observed with the ALMA Large Program “Early Planet Formation in Embedded Disks (eDisk).” We found that a dust disk model passively heated by the central protostar cannot reproduce the observed peak brightness temperature of the 1.3 mm continuum emission (∼195 K), regardless of the assumptions about the dust opacity. Our calculation suggests that viscous accretion heating in the disk is required to reproduce the observed high brightness temperature. The observed intensity profile of the 1.3 mm dust-continuum emission along the disk minor axis is skewed toward the far side of the disk. Our modeling reveals that this asymmetric intensity distribution requires flaring of the dust along the disk vertical direction with the scale height following h/r ∼ r0.3 as a function of radius. These results are in sharp contrast to those of Class II disks, which show geometrically flat dust distributions and lower dust temperatures. From our modeling of the C18O (2–1) emission, the outermost radius of the gas disk is estimated to be ∼80 au, which is larger than that of the dust disk (∼62 au), to reproduce the observed distribution of the C18O (2–1) emission in IRS 7B-a. Our modeling unveils a hot and thick dust disk plus a larger gas disk around one of the eDisk targets, which could be applicable to other protostellar sources in contrast to more evolved sources.

    DOI: 10.3847/1538-4357/ad1f57

    Scopus

  • Kido M., Takakuwa S., Saigo K., Ohashi N., Tobin J.J., Jørgensen J.K., Aikawa Y., Aso Y., Encalada F.J., Flores C., Gavino S., de Gregorio-Monsalvo I., Han I., Hirano S., Koch P.M., Kwon W., Lai S.P., Lee C.W., Lee J.E., Li Z.Y., Lin Z.Y.D., Looney L.W., Mori S., Narayanan S., Plunkett A.L., Phuong N.T., Sai J., Santamaría-Miranda A., Sharma R., Sheehan P.D., Thieme T.J., Tomida K., van ’t Hoff M.L.R., Williams J.P., Yamato Y., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). VII. Keplerian Disk, Disk Substructure, and Accretion Streamers in the Class 0 Protostar IRAS 16544-1604 in CB 68 .  Astrophysical Journal953 ( 2 ) 190 - 190   2023年8月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present observations of the Class 0 protostar IRAS 16544-1604 in CB 68 from the “Early Planet Formation in Embedded Disks (eDisk)” ALMA Large program. The ALMA observations target continuum and lines at 1.3 mm with an angular resolution of ∼5 au. The continuum image reveals a dusty protostellar disk with a radius of ∼30 au seen close to edge-on and asymmetric structures along both the major and minor axes. While the asymmetry along the minor axis can be interpreted as the effect of the dust flaring, the asymmetry along the major axis comes from a real nonaxisymmetric structure. The C18O image cubes clearly show the gas in the disk that follows a Keplerian rotation pattern around a ∼0.14 M ⊙ central protostar. Furthermore, there are ∼1500 au scale streamer-like features of gas connecting from northeast, north-northwest, and northwest to the disk, as well as the bending outflow as seen in the 12CO (2-1) emission. At the apparent landing point of the NE streamer, there is SO (65-54) and SiO (5-4) emission detected. The spatial and velocity structure of the NE streamer can be interpreted as a free-falling gas with a conserved specific angular momentum, and the detection of the SO and SiO emission at the tip of the streamer implies the presence of accretion shocks. Our eDisk observations have unveiled that the Class 0 protostar in CB 68 has a Keplerian-rotating disk with a flaring and nonaxisymmetric structure associated with accretion streamers and outflows.

    DOI: 10.3847/1538-4357/acdd7a

    Scopus

    その他リンク: https://iopscience.iop.org/article/10.3847/1538-4357/acdd7a/pdf

  • Takaishi D., Tsukamoto Y., Kido M., Takakuwa S., Misugi Y., Kudoh Y., Suto Y. .  Formation of Unipolar Outflow and Protostellar Rocket Effect in Magnetized Turbulent Molecular Cloud Cores .  Astrophysical Journal963 ( 1 )   2024年3月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    Observed protostellar outflows exhibit a variety of asymmetrical features, including remarkable unipolar outflows and bending outflows. Revealing the formation and early evolution of such asymmetrical protostellar outflows, especially the unipolar outflows, is essential for a better understanding of the star and planet formation because they can dramatically change the mass accretion and angular momentum transport to the protostars and protoplanetary disks. Here we perform three-dimensional nonideal magnetohydrodynamics simulations to investigate the formation and early evolution of the asymmetrical protostellar outflows in magnetized turbulent isolated molecular cloud cores. We find, for the first time to our knowledge, that the unipolar outflow forms even in the single low-mass protostellar system. The results show that the unipolar outflow is driven in the weakly magnetized cloud cores with the dimensionless mass-to-flux ratios of μ = 8 and 16. Furthermore, we find the protostellar rocket effect of the unipolar outflow, which is similar to the launch and propulsion of a rocket. The unipolar outflow ejects the protostellar system from the central dense region to the outer region of the parent cloud core, and the ram pressure caused by its ejection suppresses the driving of additional new outflows. In contrast, the bending bipolar outflow is driven in the moderately magnetized cloud core with μ = 4. The ratio of the magnetic to turbulent energies of a parent cloud core may play a key role in the formation of asymmetrical protostellar outflows.

    DOI: 10.3847/1538-4357/ad187a

    Scopus

  • Thieme T.J., Lai S.P., Ohashi N., Tobin J.J., Jørgensen J.K., Insa Choi J.S., Aso Y., Williams J.P., Yamato Y., Aikawa Y., de Gregorio-Monsalvo I., Han I., Kwon W., Lee C.W., Lee J.E., Li Z.Y., Lin Z.Y.D., Looney L.W., Narayanan S., Phuong N.T., Plunkett A.L., Santamaría-Miranda A., Sharma R., Takakuwa S., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). VIII. A Small Protostellar Disk around the Extremely Low Mass and Young Class 0 Protostar IRAS 15398-3359 .  Astrophysical Journal958 ( 1 )   2023年11月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    Protostellar disks are an ubiquitous part of the star formation process and the future sites of planet formation. As part of the Early Planet Formation in Embedded Disks large program, we present high angular resolution dust continuum (∼40 mas) and molecular line (∼150 mas) observations of the Class 0 protostar IRAS 15398-3359. The dust continuum is small, compact, and centrally peaked, while more extended dust structures are found in the outflow directions. We perform a 2D Gaussian fitting and find the deconvolved size and 2σ radius of the dust disk to be 4.5 × 2.8 au and 3.8 au, respectively. We estimate the gas+dust disk mass assuming optically thin continuum emission to be 0.6M J-1.8M J, indicating a very low mass disk. The CO isotopologues trace components of the outflows and inner envelope, while SO traces a compact, rotating disk-like component. Using several rotation curve fittings on the position-velocity diagram of the SO emission, the lower limits of the protostellar mass and gas disk radius are 0.022 M ⊙ and 31.2 au, respectively, from our Modified 2 single power-law fitting. A conservative upper limit of the protostellar mass is inferred to be 0.1 M ⊙. The protostellar mass accretion rate and the specific angular momentum at the protostellar disk edge are found to be in the range of (1.3-6.1) × 10−6 M ⊙ yr−1 and (1.2-3.8) × 10−4 km s−1 pc, respectively, with an age estimated between 0.4 × 104 yr and 7.5 × 104 yr. At this young age with no clear substructures in the disk, planet formation would likely not yet have started. This study highlights the importance of high-resolution observations and systematic fitting procedures when deriving dynamical properties of deeply embedded Class 0 protostars.

    DOI: 10.3847/1538-4357/ad003a

    Scopus

  • Flores C., Ohashi N., Tobin J.J., Jørgensen J.K., Takakuwa S., Li Z.Y., Lin Z.Y.D., van ’t Hoff M.L.R., Plunkett A.L., Yamato Y., Sai (Insa Choi) J., Koch P.M., Yen H.W., Aikawa Y., Aso Y., de Gregorio-Monsalvo I., Kido M., Kwon W., Lee J.E., Lee C.W., Looney L.W., Santamaría-Miranda A., Sharma R., Thieme T.J., Williams J.P., Han I., Narayanan S., Lai S.P. .  Early Planet Formation in Embedded Disks (eDisk). XII. Accretion Streamers, Protoplanetary Disk, and Outflow in the Class I Source Oph IRS 63 .  Astrophysical Journal958 ( 1 )   2023年11月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Class I source Oph IRS 63 in the context of the Early Planet Formation in Embedded Disks large program. Our ALMA observations of Oph IRS 63 show a myriad of protostellar features, such as a shell-like bipolar outflow (in 12CO), an extended rotating envelope structure (in 13CO), a streamer connecting the envelope to the disk (in C18O), and several small-scale spiral structures seen toward the edge of the dust continuum (in SO). By analyzing the velocity pattern of 13CO and C18O, we measure a protostellar mass of M ⋆ = 0.5 ± 0.2 M ⊙ and confirm the presence of a disk rotating at almost Keplerian velocity that extends up to ∼260 au. These calculations also show that the gaseous disk is about four times larger than the dust disk, which could indicate dust evolution and radial drift. Furthermore, we model the C18O streamer and SO spiral structures as features originating from an infalling rotating structure that continuously feeds the young protostellar disk. We compute an envelope-to-disk mass infall rate of ∼10−6 M ⊙ yr−1 and compare it to the disk-to-star mass accretion rate of ∼10−8 M ⊙ yr−1, from which we infer that the protostellar disk is in a mass buildup phase. At the current mass infall rate, we speculate that soon the disk will become too massive to be gravitationally stable.

    DOI: 10.3847/1538-4357/acf7c1

    Scopus

  • Narayanan S., Williams J.P., Tobin J.J., Jørgensen J.K., Ohashi N., Lin Z.Y.D., van’t Hoff M.L.R., Li Z.Y., Plunkett A.L., Looney L.W., Takakuwa S., Yen H.W., Aso Y., Flores C., Lee J.E., Lai S.P., Kwon W., de Gregorio-Monsalvo I., Sharma R., Lee C.W. .  Early Planet Formation in Embedded Disks (eDisk). X. Compact Disks, Extended Infall, and a Fossil Outburst in the Class I Oph IRS43 Binary .  Astrophysical Journal958 ( 1 )   2023年11月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present the first results from the Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Large Program toward Oph IRS43, a binary system of solar mass protostars. The 1.3 mm dust continuum observations resolve a compact disk, ∼6 au radius, around the northern component and show that the disk around the southern component is even smaller, ≲3 au. CO, 13CO, and C18O maps reveal a large cavity in a low-mass envelope that shows kinematic signatures of rotation and infall extending out to ∼2000 au. An expanding CO bubble centered on the extrapolated location of the source ∼130 yr ago suggests a recent outburst. Despite the small size of the disks, the overall picture is of a remarkably large and dynamically active region.

    DOI: 10.3847/1538-4357/acfd24

    Scopus

  • Sharma R., Jørgensen J.K., Gavino S., Ohashi N., Tobin J.J., Lin Z.Y.D., Li Z.Y., Takakuwa S., Lee C.W., Sai (insa Choi) J., Kwon W., De Gregorio-Monsalvo I., Santamaria-Miranda A., Yen H.W., Aikawa Y., Aso Y., Lai S.P., Lee J.E., Looney L.W., Phuong N.T., Thieme T.J., Williams J.P. .  Early Planet Formation in Embedded Disks (eDisk). IX. High-resolution ALMA Observations of the Class 0 Protostar R CrA IRS5N and Its Surroundings .  Astrophysical Journal954 ( 1 )   2023年9月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present high-resolution high-sensitivity observations of the Class 0 protostar RCrA IRS5N as part of the Atacama Large Milimeter/submilimeter Array large program Early Planet Formation in Embedded Disks. The 1.3 mm continuum emission reveals a flattened continuum structure around IRS5N, consistent with a protostellar disk in the early phases of evolution. The continuum emission appears smooth and shows no substructures. However, a brightness asymmetry is observed along the minor axis of the disk, suggesting that the disk is optically and geometrically thick. We estimate the disk mass to be between 0.007 and 0.02 M ⊙. Furthermore, molecular emission has been detected from various species, including C18O (2-1), 12CO (2-1), 13CO (2-1), and H2CO (30,3 - 20,2, 32,1 - 22,0, and 32,2 - 22,1). By conducting a position-velocity analysis of the C18O (2-1) emission, we find that the disk of IRS5N exhibits characteristics consistent with Keplerian rotation around a central protostar with a mass of approximately 0.3 M ⊙. Additionally, we observe dust continuum emission from the nearby binary source IRS5a/b. The emission in 12CO toward IRS5a/b seems to emanate from IRS5b and flow into IRS5a, suggesting material transport between their mutual orbits. The lack of a detected outflow and large-scale negatives in 12CO observed toward IRS5N suggests that much of the flux from IRS5N is being resolved out. Using a 1D radiative transfer model, we infer the mass of the envelope surrounding IRS5N to be 1/41.2 M ⊙. Due to this substantial surrounding envelope, the central IRS5N protostar is expected to be significantly more massive in the future.

    DOI: 10.3847/1538-4357/ace35c

    Scopus

  • Aso Y., Kwon W., Ohashi N., Jørgensen J.K., Tobin J.J., Aikawa Y., de Gregorio-Monsalvo I., Han I., Kido M., Koch P.M., Lai S.P., Lee C.W., Lee J.E., Li Z.Y., Lin Z.Y.D., Looney L.W., Narayanan S., Phuong N.T., Insa Choi J.S., Saigo K., Santamaría-Miranda A., Sharma R., Takakuwa S., Thieme T.J., Tomida K., Williams J.P., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). VI. Kinematic Structures around the Very-low-mass Protostar IRAS 16253-2429 .  Astrophysical Journal954 ( 1 )   2023年9月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    Precise estimates of protostellar masses are crucial to characterize the formation of stars of low masses down to brown dwarfs (BDs; M * < 0.08 M ☉). The most accurate estimation of protostellar mass uses the Keplerian rotation in the circumstellar disk around the protostar. To apply the Keplerian rotation method to a protostar at the low-mass end, we have observed the Class 0 protostar IRAS 16253-2429 using the Atacama Large Millimeter/submillimeter Array (ALMA) in the 1.3 mm continuum at an angular resolution of 0.″07 (10 au), and in the 12CO, C18O, 13CO (J = 2-1), and SO (J N = 65−54) molecular lines, as part of the ALMA Large Program Early Planet Formation in Embedded Disks project. The continuum emission traces a nonaxisymmetric, disk-like structure perpendicular to the associated 12CO outflow. The position-velocity (PV) diagrams in the C18O and 13CO lines can be interpreted as infalling and rotating motions. In contrast, the PV diagram along the major axis of the disk-like structure in the 12CO line allows us to identify Keplerian rotation. The central stellar mass and the disk radius are estimated to be ∼0.12-0.17 M ☉ and ∼13-19 au, respectively. The SO line suggests the existence of an accretion shock at a ring (r ∼ 28 au) surrounding the disk and a streamer from the eastern side of the envelope. IRAS 16253-2429 is not a proto-BD but has a central stellar mass close to the BD mass regime, and our results provide a typical picture of such very-low-mass protostars.

    DOI: 10.3847/1538-4357/ace624

    Scopus

  • Sai J., Yen H.W., Ohashi N., Tobin J.J., Jørgensen J.K., Takakuwa S., Saigo K., Aso Y., Lin Z.Y.D., Koch P.M., Aikawa Y., Flores C., De Gregorio-Monsalvo I., Han I., Kido M., Kwon W., Lai S.P., Lee C.W., Lee J.E., Li Z.Y., Looney L.W., Mori S., Phuong N.T., Santamaria-Miranda A., Sharma R., Thieme T.J., Tomida K., Williams J.P. .  Early Planet Formation in Embedded Disks (eDisk). V. Possible Annular Substructure in a Circumstellar Disk in the Ced110 IRS4 System .  Astrophysical Journal954 ( 1 )   2023年9月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We have observed the Class 0/I protostellar system Ced110 IRS4 at an angular resolution of 0.″05 ( 1/410 au) as part of the Atacama Large Millimeter/submillimeter Array large program, Early Planet Formation in Embedded Disks. The 1.3 mm dust continuum emission reveals that Ced110 IRS4 is a binary system with a projected separation of 1/4250 au. The continuum emissions associated with the main source and its companion, named Ced110 IRS4A and IRS4B, respectively, exhibit disk-like shapes and likely arise from dust disks around the protostars. The continuum emission of Ced110 IRS4A has a radius of 1/4110 au ( 1/40.″6) and shows bumps along its major axis with an asymmetry. The bumps can be interpreted as a shallow, ring-like structure at a radius of 1/440 au ( 1/40.″2) in the continuum emission, as demonstrated from two-dimensional intensity distribution models. A rotation curve analysis on the C18O and 13CO J = 2-1 lines reveals the presence of a Keplerian disk within a radius of 120 au around Ced110 IRS4A, which supports the interpretation that the dust continuum emission arises from a disk. The ring-like structure in the dust continuum emission might indicate a possible annular substructure in the surface density of the embedded disk, although the possibility that it is an apparent structure due to the optically thick continuum emission cannot be ruled out.

    DOI: 10.3847/1538-4357/ace52d

    Scopus

  • Taniguchi K., Majumdar L., Caselli P., Takakuwa S., Hsieh T.H., Saito M., Li Z.Y., Dobashi K., Shimoikura T., Nakamura F., Tan J.C., Herbst E. .  Chemical Differentiation around Five Massive Protostars Revealed by ALMA: Carbon-chain Species and Oxygen/Nitrogen-bearing Complex Organic Molecules .  Astrophysical Journal, Supplement Series267 ( 1 )   2023年7月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal, Supplement Series  

    We present Atacama Large Millimeter/submillimeter Array Band 3 data toward five massive young stellar objects (MYSOs), and investigate relationships between unsaturated carbon-chain species and saturated complex organic molecules (COMs). An HC5N (J = 35-34) line has been detected from three MYSOs, where nitrogen (N)-bearing COMs (CH2CHCN and CH3CH2CN) have been detected. The HC5N spatial distributions show compact features and match with a methanol (CH3OH) line with an upper-state energy around 300 K, which should trace hot cores. The hot regions are more extended around the MYSOs where N-bearing COMs and HC5N have been detected compared to two MYSOs without these molecular lines, while there are no clear differences in the bolometric luminosity and temperature. We run chemical simulations of hot-core models with a warm-up stage, and compare with the observational results. The observed abundances of HC5N and COMs show good agreements with the model at the hot-core stage with temperatures above 160 K. These results indicate that carbon-chain chemistry around the MYSOs cannot be reproduced by warm carbon-chain chemistry, and a new type of carbon-chain chemistry occurs in hot regions around MYSOs.

    DOI: 10.3847/1538-4365/acd110

    Scopus

  • van ’t Hoff M.L.R., Tobin J.J., Li Z.Y., Ohashi N., Jørgensen J.K., Lin Z.Y.D., Aikawa Y., Aso Y., de Gregorio-Monsalvo I., Gavino S., Han I., Koch P.M., Kwon W., Lee C.W., Lee J.E., Looney L.W., Narayanan S., Plunkett A., Insa Choi J.S., Santamaría-Miranda A., Sharma R., Sheehan P.D., Takakuwa S., Thieme T.J., Williams J.P., Lai S.P., Phuong N.T., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). III. A First High-resolution View of Submillimeter Continuum and Molecular Line Emission toward the Class 0 Protostar L1527 IRS .  Astrophysical Journal951 ( 1 )   2023年7月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    Studying the physical and chemical conditions of young embedded disks is crucial to constrain the initial conditions for planet formation. Here we present Atacama Large Millimeter/submillimeter Array observations of dust continuum at ∼0.″06 (8 au) resolution and molecular line emission at ∼0.″17 (24 au) resolution toward the Class 0 protostar L1527 IRS from the Large Program eDisk (Early Planet Formation in Embedded Disks). The continuum emission is smooth without substructures but asymmetric along both the major and minor axes of the disk as previously observed. The detected lines of 12CO, 13CO, C18O, H2CO, c-C3H2, SO, SiO, and DCN trace different components of the protostellar system, with a disk wind potentially visible in 12CO. The 13CO brightness temperature and the H2CO line ratio confirm that the disk is too warm for CO freezeout, with the snowline located at ∼350 au in the envelope. Both molecules show potential evidence of a temperature increase around the disk-envelope interface. SO seems to originate predominantly in UV-irradiated regions such as the disk surface and the outflow cavity walls rather than at the disk-envelope interface as previously suggested. Finally, the continuum asymmetry along the minor axis is consistent with the inclination derived from the large-scale (100″ or 14,000 au) outflow, but opposite to that based on the molecular jet and envelope emission, suggesting a misalignment in the system. Overall, these results highlight the importance of observing multiple molecular species in multiple transitions to characterize the physical and chemical environment of young disks.

    DOI: 10.3847/1538-4357/accf87

    Scopus

  • Lin Z.Y.D., Li Z.Y., Tobin J.J., Ohashi N., Jørgensen J.K., Looney L.W., Aso Y., Takakuwa S., Aikawa Y., van’t Hoff M.L.R., de Gregorio-Monsalvo I., Encalada F.J., Flores C., Gavino S., Han I., Kido M., Koch P.M., Kwon W., Lai S.P., Lee C.W., Lee J.E., Phuong N.T., Sai (Insa Choi) J., Sharma R., Sheehan P., Thieme T.J., Williams J.P., Yamato Y., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). II. Limited Dust Settling and Prominent Snow Surfaces in the Edge-on Class I Disk IRAS 04302+2247 .  Astrophysical Journal951 ( 1 )   2023年7月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    While dust disks around optically visible, Class II protostars are found to be vertically thin, when and how dust settles to the midplane are unclear. As part of the Atacama Large Millimeter/submillimeter Array large program, Early Planet Formation in Embedded Disks, we analyze the edge-on, embedded, Class I protostar IRAS 04302+2247, also nicknamed the “Butterfly Star.” With a resolution of 0.″05 (8 au), the 1.3 mm continuum shows an asymmetry along the minor axis that is evidence of an optically thick and geometrically thick disk viewed nearly edge-on. There is no evidence of rings and gaps, which could be due to the lack of radial substructure or the highly inclined and optically thick view. With 0.″1 (16 au) resolution, we resolve the 2D snow surfaces, i.e., the boundary region between freeze-out and sublimation, for 12CO J = 2-1, 13CO J = 2-1, C18O J = 2-1, H 2CO J = 30,3-20,2, and SO J = 65-54, and constrain the CO midplane snow line to ∼130 au. We find Keplerian rotation around a protostar of 1.6 ± 0.4 M ⊙ using C18O. Through forward ray-tracing using RADMC-3D, we find that the dust scale height is ∼6 au at a radius of 100 au from the central star and is comparable to the gas pressure scale height. The results suggest that the dust of this Class I source has yet to vertically settle significantly.

    DOI: 10.3847/1538-4357/acd5c9

    Scopus

  • Ohashi N., Tobin J.J., Jørgensen J.K., Takakuwa S., Sheehan P., Aikawa Y., Li Z.Y., Looney L.W., Williams J.P., Aso Y., Sharma R., Sai (Insa Choi) J., Yamato Y., Lee J.E., Tomida K., Yen H.W., Encalada F.J., Flores C., Gavino S., Kido M., Han I., Lin Z.Y.D., Narayanan S., Phuong N.T., Santamaría-Miranda A., Thieme T.J., van ’t Hoff M.L.R., de Gregorio-Monsalvo I., Koch P.M., Kwon W., Lai S.P., Lee C.W., Plunkett A., Saigo K., Hirano S., Lam K.H., Mori S. .  Early Planet Formation in Embedded Disks (eDisk). I. Overview of the Program and First Results .  Astrophysical Journal951 ( 1 ) 8 - 8   2023年6月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present an overview of the Large Program, “Early Planet Formation in Embedded Disks (eDisk),” conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The ubiquitous detections of substructures, particularly rings and gaps, in protoplanetary disks around T Tauri stars raise the possibility that at least some planet formation may have already started during the embedded stages of star formation. In order to address exactly how and when planet formation is initiated, the program focuses on searching for substructures in disks around 12 Class 0 and 7 Class I protostars in nearby (<200 pc) star-forming regions through 1.3 mm continuum observations at a resolution of ∼7 au (0.″04). The initial results show that the continuum emission, mostly arising from dust disks around the sample protostars, has relatively few distinctive substructures, such as rings and spirals, in marked contrast to Class II disks. The dramatic difference may suggest that substructures quickly develop in disks when the systems evolve from protostars to Class II sources, or alternatively that high optical depth of the continuum emission could obscure internal structures. Kinematic information obtained through CO isotopologue lines and other lines reveals the presence of Keplerian disks around protostars, providing us with crucial physical parameters, in particular, the dynamical mass of the central protostars. We describe the background of the eDisk program, the sample selection and their ALMA observations, and the data reduction, and we also highlight representative first-look results.

    DOI: 10.3847/1538-4357/acd384

    Scopus

    その他リンク: https://iopscience.iop.org/article/10.3847/1538-4357/acd384/pdf

  • Yamato Y., Aikawa Y., Ohashi N., Tobin J.J., Jørgensen J.K., Takakuwa S., Aso Y., Insa Choi J.S., Flores C., de Gregorio-Monsalvo I., Hirano S., Han I., Kido M., Koch P.M., Kwon W., Lai S.P., Lee C.W., Lee J.E., Li Z.Y., Lin Z.Y.D., Looney L.W., Mori S., Narayanan S., Phuong N.T., Saigo K., Santamaría-Miranda A., Sharma R., Thieme T.J., Tomida K., van ’t Hoff M.L.R., Yen H.W. .  Early Planet Formation in Embedded Disks (eDisk). IV. The Ringed and Warped Structure of the Disk around the Class I Protostar L1489 IRS .  Astrophysical Journal951 ( 1 ) 11 - 11   2023年6月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    Constraining the physical and chemical structure of young embedded disks is crucial for understanding the earliest stages of planet formation. As part of the Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Large Program, we present high spatial resolution (∼0.″1 or ∼15 au) observations of the 1.3 mm continuum and 13CO J = 2-1, C18O J = 2-1, and SO J N = 65-54 molecular lines toward the disk around the Class I protostar L1489 IRS. The continuum emission shows a ring-like structure at 56 au from the central protostar and tenuous, optically thin emission extending beyond ∼300 au. The 13CO emission traces the warm disk surface, while the C18O emission originates from near the disk midplane. The coincidence of the radial emission peak of C18O with the dust ring may indicate a gap-ring structure in the gaseous disk as well. The SO emission shows a highly complex distribution, including a compact, prominent component at ≲30 au, which is likely to originate from thermally sublimated SO molecules. The compact SO emission also shows a velocity gradient along a direction tilted slightly (∼15°) with respect to the major axis of the dust disk, which we interpret as an inner warped disk in addition to the warp around ∼200 au suggested by previous work. These warped structures may be formed by a planet or companion with an inclined orbit, or by a gradual change in the angular momentum axis during gas infall.

    DOI: 10.3847/1538-4357/accd71

    Scopus

    その他リンク: https://iopscience.iop.org/article/10.3847/1538-4357/accd71/pdf

  • Kitayama T., Ueda S., Okabe N., Akahori T., Hilton M., Hughes J.P., Ichinohe Y., Kohno K., Komatsu E., Lin Y.T., Miyatake H., Oguri M., Sifón C., Takakuwa S., Takizawa M., Tsutsumi T., van Marrewijk J., Wollack E.J. .  Galaxy clusters at z ∼ 1 imaged by ALMA with the Sunyaev–Zel’dovich effect .  Publications of the Astronomical Society of Japan75 ( 2 ) 311 - 337   2023年4月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Publications of the Astronomical Society of Japan  

    We present high angular resolution measurements of the thermal Sunyaev–Zel’dovich effect (SZE) toward two galaxy clusters, RCS J2319+0038 at z = 0.9 and HSC J0947−0119 at z = 1.1, by the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 3. They are supplemented with available Chandra X-ray data, optical data taken by Hyper Suprime-Cam on Subaru, and millimeter-wave SZE data from the Atacama Cosmology Telescope. Taking into account departures from spherical symmetry, we have reconstructed non-parametrically the inner pressure profile of two clusters as well as electron temperature and density profiles for RCS J2319+0038. This is one of the first such measurements for an individual cluster at z ≳ 0.9. We find that the inner pressure profile of both clusters is much shallower than that of local cool-core clusters. Our results consistently suggest that RCS J2319+0038 hosts a weak cool core, where radiative cooling is less significant than in local cool cores. On the other hand, HSC J0947−0119 exhibits an even shallower pressure profile than RCS J2319+0038 and is more likely to be a non-cool-core cluster. The SZE centroid position is offset by more than 140 h−170 kpc from the peaks of galaxy distribution in HSC J0947−0119, suggesting a stronger influence of mergers in this cluster. We conclude that these distant clusters are at a very early stage of developing the cool cores typically found in clusters at lower redshifts.

    DOI: 10.1093/pasj/psac110

    Scopus

  • Yen H.W., Koch P.M., Lee C.F., Hirano N., Ohashi N., Insa Choi J.S., Takakuwa S., Tang Y.W., Tatematsu K., Zhao B. .  Increasing Mass-to-flux Ratio from the Dense Core to the Protostellar Envelope around the Class 0 Protostar HH 211 .  Astrophysical Journal942 ( 1 )   2023年1月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    To study the transportation of magnetic flux from large to small scales in protostellar sources, we analyzed the Nobeyama 45 m N2H+ (1-0), JCMT 850 μm polarization, and Atacama Large Millimeter/submillimeter Array (ALMA) C18O (2-1) and 1.3 and 0.8 mm (polarized) continuum data of the Class 0 protostar HH 211. The magnetic field strength in the dense core on a 0.1 pc scale was estimated with the single-dish line and polarization data using the Davis-Chandrasekhar-Fermi method, and that in the protostellar envelope on a 600 au scale was estimated from the force balance between the gravity and magnetic field tension by analyzing the gas kinematics and magnetic field structures with the ALMA data. Our analysis suggests that from 0.1 pc-600 au scales, the magnetic field strength increases from 40-107 μG to 0.3-1.2 mG with a scaling relation between the magnetic field strength and density of B ∝ ρ 0.36±0.08, and the mass-to-flux ratio increases from 1.2-3.7 to 9.1-32.3. The increase in the mass-to-flux ratio could suggest that the magnetic field is partially decoupled from the neutral matter between 0.1 pc and 600 au scales, and hint at efficient ambipolar diffusion in the infalling protostellar envelope in HH 211, which is the dominant nonideal magnetohydrodynamic effect considering the density on these scales. Thus, our results could support the scenario of efficient ambipolar diffusion enabling the formation of the 20 au Keplerian disk in HH 211.

    DOI: 10.3847/1538-4357/aca47f

    Scopus

  • Ohata Y., Kakimoto H., Seki Y., Ishihara Y., Nakano Y., Yamamoto K., Takeyari S., Fujiwara M., Kitaoka T., Takakuwa S., Kubota T., Ozono K. .  Pathogenic variants of the GNAS gene introduce an abnormal amino acid sequence in the β6 strand/α5 helix of Gsα, causing pseudohypoparathyroidism type 1A and pseudopseudohypoparathyroidism in two unrelated Japanese families .  Bone Reports17   101637   2022年12月

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    記述言語:日本語   出版者・発行元:Bone Reports  

    Pseudohypoparathyroidism 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are caused by loss-of-function variants of GNAS, which encodes Gsα. We present two unrelated Japanese families with PHP1A and PPHP harboring unreported pathogenic variants of GNAS (c.1141delG, p.Asp381Thrfs*23 and c.1117delC, p.Arg373Alafs*31). These variants introduce abnormal amino acids in the β6 strand/α5 helix of Gsα, which interact with G protein coupling receptor (GPCR). We conclude that these variants alter the association of Gsα with GPCR and cause PHP1A or PPHP.

    DOI: 10.1016/j.bonr.2022.101637

    Scopus

    PubMed

  • Sheehan P.D., Tobin J.J., Li Z.Y., van ’t Hoff M.L.R., Jørgensen J.K., Kwon W., Looney L.W., Ohashi N., Takakuwa S., Williams J.P., Aso Y., Gavino S., Gregorio-Monsalvo I.d., Han I., Lee C.W., Plunkett A., Sharma R., Aikawa Y., Lai S.P., Lee J.E., Lin Z.Y.D., Saigo K., Tomida K., Yen H.W. .  A VLA View of the Flared, Asymmetric Disk around the Class 0 Protostar L1527 IRS .  Astrophysical Journal934 ( 2 )   2022年8月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present high-resolution Karl G. Jansky Very Large Array (VLA) observations of the protostar L1527 IRS at 7 mm, 1.3 cm, and 2 cm wavelengths. We detect the edge-on dust disk at all three wavelengths and find that it is asymmetric, with the southern side of the disk brighter than the northern side. We confirm this asymmetry through analytic modeling and also find that the disk is flared at 7 mm. We test the data against models including gap features in the intensity profile, and though we cannot rule such models out, they do not provide a statistically significant improvement in the quality of fit to the data. From these fits, we can, however, place constraints on allowed properties of any gaps that could be present in the true, underlying intensity profile. The physical nature of the asymmetry is difficult to associate with physical features owing to the edge-on nature of the disk, but it could be related to spiral arms or asymmetries seen in other imaging of more face-on disks.

    DOI: 10.3847/1538-4357/ac7a3b

    Scopus

  • Taniguchi K., Tanaka K.E.I., Zhang Y., Fedriani R., Tan J.C., Takakuwa S., Nakamura F., Saito M., Majumdar L., Herbst E. .  Vibrationally Excited Lines of HC<inf>3</inf>N Associated with the Molecular Disk around the G24.78+0.08 A1 Hypercompact H ii Region .  Astrophysical Journal931 ( 2 )   2022年6月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hypercompact H ii region G24.78+0.08 A1 (G24 HC H ii) and report the detection of vibrationally excited lines of HC3N (v 7 = 2, J = 24-23). The spatial distribution and kinematics of a vibrationally excited line of HC3N (v 7 = 2, J = 24-23, l = 2e) are found to be similar to the CH3CN vibrationally excited line (v 8 = 1), which indicates that the HC3N emission is tracing the disk around the G24 HC H ii region previously identified by the CH3CN lines. We derive the 13CH3CN/HC13CCN abundance ratios around G24 and compare them to the CH3CN/HC3N abundance ratios in disks around Herbig Ae and T Tauri stars. The 13CH3CN/HC13CCN ratios around G24 (∼3.0-3.5) are higher than the CH3CN/HC3N ratios in the other disks (∼0.03-0.11) by more than 1 order of magnitude. The higher CH3CN/HC3N ratios around G24 suggest that the thermal desorption of CH3CN in the hot dense gas and efficient destruction of HC3N in the region irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally excited HC3N lines can be used as a disk tracer of massive protostars at the HC H ii region stage, and the combination of these nitrile species will provide information of not only chemistry but also physical conditions of the disk structures.

    DOI: 10.3847/1538-4357/ac69d1

    Scopus

  • Chiong C.C., Nakamura F., Nishimura A., Burns R.A., Chien C., Dobashi K., Fujii Y., Ho C.T., Huang T., Hwang Y.J., Jian S.T., Kawabe R., Kimura K., Liu S.Y., Lai S.P., Ogawa H., Okada N., Kameno S., Shimoikura T., Takakuwa S., Taniguchi K., Wang W.H., Yeh Y.T., Yamasaki Y., Yonekura Y. .  Extended Q-band (eQ) receiver for Nobeyama 45-m Telescope .  Proceedings of SPIE - The International Society for Optical Engineering12190   2022年査読 国際共著

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering  

    The Ka-/Q-band in the microwave region of the electromagnetic spectrum is important for astrophysical and astrochemical research, particularly in the subfield of interstellar medium (ISM). The two bands cover not only the fundamental lines of the abundant dense gas tracer CS and its isotopologues but also a vast number of transitions of relatively large, long-chain, and/or complex organic species. Here, through a Taiwan-Japan collaboration, an extended Q-band (30-50GHz) receiver is built for Nobeyama 45-m telescope. The receiver front-end was installed at Nobeyama 45-m telescope in Nov. 2021 and obtained its first light in the same month. Commissioning and science verification (CSV) of the receiver was conducted in the first half of 2022. After commissioning, this receiver will be the only one in the world providing capability to cover 3 Zeeman transitions simultaneously at 7mm wavelength installed at large single dish telescope. It will be one of the most powerful facilities to explore the magnetic fields towards the pre-protostellar cores.

    DOI: 10.1117/12.2629811

    Scopus

  • Taniguchi K. .  Chemical Compositions in the Vicinity of Protostars in Ophiuchus .  Astrophysical Journal922 ( 2 )   2021年12月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We have analyzed Atacama Large Millimeter/submillimeter Array Cycle 4 Band 6 data toward two young stellar objects (YSOs), Oph-emb5 and Oph-emb9, in the Ophiuchus star-forming region. The YSO Oph-emb5 is located in a relatively quiescent region, whereas Oph-emb9 is irradiated by a nearby bright Herbig Be star. Molecular lines from cyclic-C3H2 (c-C3H2), H2CO, CH3OH, 13CO, C18O, and DCO+ have been detected from both sources, while DCN is detected only in Oph-emb9. Around Oph-emb5, c-C3H2 is enhanced at the west side, relative to the IR source, whereas H2CO and CH3OH are abundant at the east side. In the field of Oph-emb9, moment 0 maps of the c-C3H2 lines show a peak at the eastern edge of the field of view, which is irradiated by the Herbig Be star. Moment 0 maps of CH3OH and H2CO show peaks farther from the bright star. We derive the N(c-C3H2)/N(CH3OH) column density ratios at the peak positions of c-C3H2 and CH3OH near each YSO, which are identified based on their moment 0 maps. The N(c-C3H2)/N(CH3OH) ratio at the c-C3H2 peak is significantly higher than at the CH3OH peak by a factor of ∼19 in Oph-emb9, while the difference in this column density ratio between these two positions is a factor of ∼2.6 in Oph-emb5. These differences are attributed to the efficiency of the photon-dominated region chemistry in Oph-emb9. The higher DCO+ column density and the detection of DCN in Oph-emb9 are also discussed in the context of UV irradiation flux.

    DOI: 10.3847/1538-4357/ac214e

    Scopus

  • Ichikawa T. .  Misaligned circumstellar disks and orbital motion of the young binary xz tau .  Astrophysical Journal919 ( 1 )   2021年9月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We report our analyses of the multi-epoch (2015-2017) Atacama Large Millimeter/submillimeter Array (ALMA) archival data of the Class II binary system XZ Tau at Bands 3, 4, and 6. The millimeter dust-continuum images show compact, unresolved (r 15 au) circumstellar disks (CSDs) around the individual binary stars, XZ Tau A and B, with a projected separation of ∼39 au. The 12CO (2-1) emission associated with those CSDs traces the Keplerian rotations, whose rotational axes are misaligned with each other (P.A. ∼-5° for XZ Tau A and ∼130° for XZ Tau B). The similar systemic velocities of the two CSDs (VLSR ∼ 6.0 km s-1) suggest that the orbital plane of the binary stars is close to the plane of the sky. From the multi-epoch ALMA data, we have also identified the relative orbital motion of the binary. Along with the previous NIR data, we found that the elliptical orbit (e = - 0.742+0.034 0.025, = a 0. 172+0. 003 0. 002, and w = -54 .2+ 4 .7 2.0) is preferable to the circular orbit. Our results suggest that the two CSDs and the orbital plane of the XZ Tau system are all misaligned with each other, and possible mechanisms to produce such a configuration are discussed. Our analyses of the multi-epoch ALMA archival data demonstrate the feasibility of time-domain science with ALMA.

    DOI: 10.3847/1538-4357/ac0dc3

    Scopus

  • Hara C. .  Misaligned twin molecular outflows from the class 0 protostellar binary system VLA 1623A unveiled by ALMA .  Astrophysical Journal912 ( 1 ) 34 - 34   2021年5月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We present the results of ALMA observations toward the low-mass Class 0 binary system VLA 1623Aab in the Ophiuchus molecular cloud in 12CO, 13CO, and C18O(2–1) lines. Our 12CO (J = 2–1) data reveal that the VLA 1623 outflow consists of twin spatially overlapped outflows/jets. The redshifted northwestern jet exhibits three cycles of wiggle with a spatial period of 1360 ± 10 au, corresponding to a time period of 180 yr. The wiggle-like structure is also found in the position–velocity (PV) diagram, showing an amplitude in the velocity of about 0.9 km s−1. Both the period and velocity amplitude of the wiggle are roughly consistent with those expected from the binary parameters, i.e., the orbital period (460 ± 20 yr) and the Keplerian velocity (2.2 km s−1). Our 13CO and C18O images show a dense gas nature in the two centimeter/millimeter sources, VLA 1623B and W, and its relation to the outflows, and strongly support the previous interpretation that both are shocked cloudlets. The driving sources of the twin molecular outflows are, therefore, likely to be the VLA 1623Aab binary. The outflow axes of the two molecular outflows are estimated to be inclined by 70° to each other across the plane of sky, implying that protostellar disks are also misaligned by 70◦. Such nature together with a small binary separation of 34 au in one of the youngest protobinary systems seems difficult to explain by disk fragmentation in quiescent environments. Other effects such as turbulence probably play roles.

    DOI: 10.3847/1538-4357/abb810

    Scopus

    その他リンク: https://iopscience.iop.org/article/10.3847/1538-4357/abb810/pdf

  • Taniguchi K. .  Carbon-chain Chemistry versus Complex-organic-molecule Chemistry in Envelopes around Three Low-mass Young Stellar Objects in the Perseus Region .  Astrophysical Journal910 ( 2 )   2021年4月査読 国際共著

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astrophysical Journal  

    We have analyzed ALMA Cycle 5 data in Band 4 toward three low-mass young stellar objects, IRAS 03235+3004 (hereafter IRAS 03235), IRAS 03245+3002 (IRAS 03245), and IRAS 03271+3013 (IRAS 03271), in the Perseus region. The HC3N (J = 16-15; E up/k = 59.4 K) line has been detected in all of the target sources, while four CH3OH lines (E up/k = 15.4-36.3 K) have been detected only in IRAS 03245. Sizes of the HC3N distributions (∼2930-3230 au) in IRAS 03235 and IRAS 03245 are similar to those of the carbon-chain species in the warm carbon-chain chemistry (WCCC) source L1527. The size of the CH3OH emission in IRAS 03245 is ∼1760 au, which is slightly smaller than that of HC3N in this source. We compare the CH3OH/HC3N abundance ratios observed in these sources with predictions of chemical models. We confirm that the observed ratio in IRAS 03245 agrees with the modeled values at temperatures around 30-35 K, which supports the HC3N formation by the WCCC mechanism. In this temperature range, CH3OH does not thermally desorb from dust grains. Nonthermal desorption mechanisms or gas-phase formation of CH3OH seem to work efficiently around IRAS 03245. The fact that IRAS 03245 has the highest bolometric luminosity among the target sources seems to support these mechanisms, in particular the nonthermal desorption mechanisms.

    DOI: 10.3847/1538-4357/abe854

    Scopus

  • Shigehisa Takakuwa, Kazuya Saigo, Tomoaki Matsumoto, Masao Saito, Jeremy Lim, Hsi-Wei Yen, Nagayoshi Ohashi, Paul T. P. Ho, Leslie W. Looney .  Circumbinary Disks of the Protostellar Binary Systems in the L1551 Region .  The Astrophysical Journal898 ( 1 ) 10   2020年7月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/1538-4357/ab9b7c

    arXiv

  • Hsi-Wei Yen, Bo Zhao, Patrick M. Koch, Ruben Krasnopolsky, Zhi-Yun Li, Nagayoshi Ohashi, Hsien Shang, Shigehisa Takakuwa, Ya-Wen Tang .  Transition from Ordered Pinched to Warped Magnetic Field on a 100 au Scale in the Class 0 Protostar B335 .  The Astrophysical Journal893 ( 54 )   2020年4月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/1538-4357/ab7eb3

    arXiv

  • Jinshi Sai, Nagayoshi Ohashi, Kazuya Saigo, Tomoaki Matsumoto, Yusuke Aso, Shigehisa Takakuwa, Yuri Aikawa, Ippei Kurose, Hsi-Wei Yen, Kohji Tomisaka, Kengo Tomida, Masahiro N. Machida .  Disk Structure around the Class I Protostar L1489 IRS Revealed by ALMA: A Warped-disk System .  The Astrophysical Journal893 ( 51 )   2020年4月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/1538-4357/ab8065

  • Tetsu Kitayama, Shutaro Ueda, Takuya Akahori, Eiichiro Komatsu, Ryohei Kawabe, Kotaro Kohno, Shigehisa Takakuwa, Motokazu Takizawa, Takahiro Tsutsumi, Kohji Yoshikawa .  Deeply cooled core of the Phoenix galaxy cluster imaged by ALMA with the Sunyaev-Zel'dovich effect .  Publications of the Astronomical Society of Japan72 ( 2 ) 33 - 3318   2020年4月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Astronomical Society of Japan  

    We present measurements of the thermal Sunyaev-Zel'dovich effect (SZE) toward SPT-CL J2334-4243 (the Phoenix galaxy cluster) at z = 0.597 by the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 3. The SZE is imaged at 5″ resolution (corresponding to the physical scale of 23 h-1 kpc) within 200 h-1kpc from the central galaxy, with the peak signal-to-noise ratio exceeding 11. Combined with the Chandra X-ray image, the ALMA SZE data further allow for non-parametric deprojection of electron temperature, density, and entropy. Our method can minimize contamination by the central active galactic nucleus and the X-ray absorbing gas within the cluster, both of which greatly affect the X-ray spectrum.We find no significant asymmetry or disturbance in the SZE image within the current measurement errors. The detected SZE signal shows much higher central concentration than other distant galaxy clusters and agrees well with the average pressure profile of local cool-core clusters. Unlike in typical clusters at any redshift, the gas temperature drops by at least a factor of 5 toward the center.We identify ~6 × 1011M⊙cool gas with temperature ~3 keV in the inner 20 h-1kpc. Taken together, our results imply that the gas is indeed cooling efficiently and nearly isobarically down to this radius in the Phoenix cluster.

    DOI: 10.1093/pasj/psaa009

    Scopus

    arXiv

  • Yusuke Aso, Naomi Hirano, Yuri Aikawa, Masahiro N. Machida, Nagayoshi Ohashi, Masao Saito, Shigehisa Takakuwa, Hsi-Wei Yen, Jonathan P. Williams .  Protostellar Evolution in Serpens Main: Possible Origin of Disk-size Diversity .  The Astrophysical Journal887 ( 209 ) 14pp   2019年12月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/ab5284

  • Yu-Nung Su, Sheng-Yuan Liu, Zhi-Yun Li, Chin-Fei Lee, Naomi Hirano, Shigehisa Takakuwa, I.-Ta Hsieh .  The Infall Motion in the Low-mass Protostellar Binary NGC 1333 IRAS 4A1/4A2 .  The Astrophysical Journal885 ( 98 ) 16pp   2019年11月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/ab4818

  • Hsi-Wei Yen, Pin-Gao Gu, Naomi Hirano, Patrick M. Koch, Chin-Fei Lee, Hauyu Baobab Liu, Shigehisa Takakuwa .  HL Tau Disk in HCO+ (3-2) and (1-0) with ALMA: Gas Density, Temperature, Gap, and One-arm Spiral .  The Astrophysical Journal880 ( 69 ) 18pp   2019年8月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/ab29f8

  • Kazuhito Motogi, Tomoya Hirota, Masahiro N. Machida, Yoshinori Yonekura, Mareki Honma, Shigehisa Takakuwa, Satoki Matsushita .  The First Bird’s-eye View of a Gravitationally Unstable Accretion Disk in High-mass Star Formation .  Astrophysical Journal Letters877 ( L25 ) 8pp   2019年6月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/2041-8213/ab212f

  • M. Yamagishi, C. Hara, R. Kawabe, F. Nakamura, T. Kamazaki, T. Takekoshi, Y. Shimajiri, H. Nomura, S. Takakuwa, and J. Di Francesco .  ALMA Observations of Layered Structures due to CO Selective Dissociation in the rho Ophiuchi A Plane-parallel PDR .  The Astrophysical Journal875 ( 1 ) 62 - 62   2019年4月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/ab0d80

    arXiv

  • Hsi-Wei Yen, Shigehisa Takakuwa, Pin-Gao Gu, Naomi Hirano, Chin-Fei Lee, Hauyu Baobab Liu, Sheng-Yuan Liu, and Chun-Ju Wu .  Signs of outflow feedback from a nearby young stellar object on the protostellar envelope around HL Tauri .  Astronomy and Astrophysics623 ( A96 )   2019年3月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDP Sciences  

    DOI: 10.1051/0004-6361/201834209

    arXiv

  • Dipen Sahu, Sheng-Yuan Liu, Yu-Nung Su, Zhi-Yun Li, Chin-Fei Lee, Naomi Hirano, and Shigehisa Takakuwa .  Implications of a Hot Atmosphere/Corino from ALMA Observations toward NGC 1333 IRAS 4A1 .  The Astrophysical Journal872 ( 2 ) 196 - 196   2019年2月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aaffda

    arXiv

  • Hsi-Wen Yen, Bo Zhao, I.-Ta Hsieh, Patrick Koch, Ruben Krasnopolsky, Chin-Fei Lee, Zhi-Yun Li, Sheng-Yuan Liu, Nagayoshi Ohashi, Shigehisa Takakuwa, and Ya-Wen Tang .  JCMT POL-2 and ALMA Polarimetric Observations of 6000-100 au Scales in the Protostar B335: Linking Magnetic Field and Gas Kinematics in Observations and MHD Simulations .  The Astrophysical Journal871 ( 2 ) 243 - 243   2019年2月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aafb6c

    arXiv

  • Takeshi Kamazaki, Fumitaka Nakamura, Rhohei Kawabe, Chihomi Hara, Shigehisa Takakuwa, Naomi Hirano, James Di Francesco, Rachel Friesen, and Motohide Tamura .  ALMA Observations of the rho Ophiuchus B2 Region. I. Molecular Outflows and Their Driving Sources .  The Astrophysical Journal871 ( 1 ) 86 - 86   2019年1月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aaf857

  • Tomoaki Matsumoto, Kazuya Saigo, and Shigehisa Takakuwa .  Structure of a Protobinary System: An Asymmetric Circumbinary Disk and Spiral Arms .  The Astrophysical Journal871 ( 1 ) 36 - 36   2019年1月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aaf6ab

    arXiv

  • Chun-Ju Wu, Naomi Hirano, Shigehisa Takakuwa, Hsi-Wei Yen, and Yusuke Aso .  Physical and Chemical Conditions of the Protostellar Envelope and the Protoplanetary Disk in HL Tau .  The Astrophysical Journal869 ( 1 ) 59 - 59   2018年12月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aaed42

    arXiv

  • Shutaro Ueda, Tetsu Kitayama, Masamune Oguri, Eiichiro Komatsu, Takuya Akahori, Daisuke Iono, Takumi Izumi, Ryohei Kawabe, Kotaro Kohno, Hiroshi Matsuo, Naomi Ota, Yasushi Suto, Shigehisa Takakuwa, Motokazu Takizawa, Takahiro Tsutsumi, & Kohji Yoshikawa .  A Cool Core Disturbed: Observational Evidence for the Coexistence of Subsonic Sloshing Gas and Stripped Shock-heated Gas around the Core of RX J1347.5–1145 .  The Astrophysical Journal866 ( 48 ) 13pp   2018年10月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aadd9d

    arXiv

  • Ryohei Kawabe, Chihomi Hara, Fumitaka Nakamura, Kazuya Saigo, Takeshi Kamazaki, Yoshito Shimajiri, Kengo Tomida, Shigehisa Takakuwa, Yohko Tsuboi, Masahiro N. Machida, James Di Francesco, Rachel Friesen, Naomi Hirano, Yumiko Oasa, Motohide Tamura, Yoichi Tamura, Takashi Tsukagoshi, & David J. Wilner .  Extremely Dense Cores Associated with Chandra Sources in Ophiuchus A: Forming Brown Dwarfs Unveiled? .  The Astrophysical Journal866 ( 141 ) 15pp   2018年10月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aae153

    arXiv

  • Shigehisa Takakuwa, Yusuke Tsukamoto, Kazuya Saigo, & Masao Saito .  Possible Counterrotation between the Disk and Protostellar Envelope around the Class I Protostar IRAS 04169+2702 .  The Astrophysical Journal865 ( 51 ) 17pp   2018年9月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aadb93

    arXiv

  • Yusuke Aso, Naomi Hirano, Yuri Aikawa, Masahiro N. Machida, Shigehisa Takakuwa, Hsi-Wei Yen, & Jonathan P. Williams .  The Distinct Evolutionary Nature of Two Class 0 Protostars in Serpens Main SMM4 .  The Astrophysical Journal863 ( 19 ) 16pp   2018年8月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP  

    DOI: 10.3847/1538-4357/aacf9b

    arXiv

  • Hsi-Wei Yen, Bo Zhao, Patrick M. Koch, Ruben Krasnopolsky, Zhi-Yun Li, Nagayoshi Ohashi, & Shigehisa Takakuwa .  Constraint on ion-neutral drift velocity in the Class 0 protostar B335 from ALMA observations .  Astronomy and Astrophysics615 ( A58 ) 11pp   2018年7月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDP Sciences  

    DOI: 10.1051/0004-6361/201732195

    arXiv

  • Patrick M. Koch, Ya-Wen Tang, Paul T. P. Ho, Hsi-Wei Yen, Yu-Nung Su, Shigehisa Takakuwa .  Polarization Properties and Magnetic Field Structures in the High-mass Star-forming Region W51 Observed with ALMA .  The Astrophysical Journal855 ( 39 ) 19pp   2018年3月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    DOI: 10.3847/1538-4357/aaa4c1

    arXiv

  • Hsi-Wei Yen, Shigehisa Takakuwa, You-Hua Chu, Naomi Hirano, Paul T. P. Ho, Kazuhiro D. Kanagawa, Chin-Fei Lee, Hauyu Baobab Liu, Sheng-Yuan Liu, Tomoaki Matsumoto, Satoki Matsushita, Takayuki Muto, Kazuya Saigo, Ya-Wen Tang, Alfonso Trejo, and Chun-Ju Wu .  1000 au Exterior Arcs Connected to the Protoplanetary Disk around HL Tauri .  Astronomy & Astrophysics608   A134   2017年12月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDP Sciences  

    DOI: 10.1051/0004-6361/201730894

  • Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro N. Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen, Jonathan P. Williams .  ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster .  The Astrophysical Journal Letters850 ( L2 ) 6pp   2017年11月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/2041-8213/aa9701

  • Yusuke Aso, Nagayoshi Ohashi, Yuri Aikawa, Masahiro N. Machida, Kazuya Saigo, Masao Saito, Shigehisa Takakuwa, Kengo Tomida, Kohji Tomisaka, Hsi-Wei Yen .  ALMA Observations of the Protostar L1527 IRS: Probing Details of the Disk and the Envelope Structures .  The Astrophysical Journal849 ( 56 ) 15pp   2017年11月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/1538-4357/aa8264

  • Matsumoto T. .  Theoretical Models of Protostellar Binary and Multiple Systems with AMR Simulations .  Journal of Physics: Conference Series837 ( 1 )   2017年5月

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    出版者・発行元:Journal of Physics: Conference Series  

    DOI: 10.1088/1742-6596/837/1/012009

    Scopus

  • Shigehisa Takakuwa, Kazuya Saigo, Tomoaki Matsumoto, Masao Saito, Jeremy Lim, Tomoyuki Hanawa, Hsi-Wei Yen, & Paul T. P. Ho .  Spiral Arms, Infall, and Misalignment of the Circumbinary Disk from the Circumstellar Disks in the Protostellar Binary System L1551 NE .  The Astrophysical Journal837 ( 86 ) 14pp   2017年3月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/1538-4357/aa6116

    arXiv

  • Hsi-Wei Yen, Patrick M. Koch, Shigehisa Takakuwa, Ruben Krasnopolsky, Nagayoshi Ohashi, and Yusuke Aso .  Signs of Early-stage Disk Growth Revealed with ALMA .  The Astrophysical Journal834 ( 178 ) 23pp   2017年1月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Physics  

    DOI: 10.3847/1538-4357/834/2/178

    arXiv

  • Koch P.M. .  Magnetic fields from filaments to cores .  Memorie della Societa Astronomica Italiana - Journal of the Italian Astronomical Society88 ( 4 ) 557 - 559   2017年

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    出版者・発行元:Memorie della Societa Astronomica Italiana - Journal of the Italian Astronomical Society  

    Scopus

  • Gigi Y. C. Leung, Jeremy Lim, and Shigehisa Takakuwa .  Tracing Infall and Rotation along the Outflow Cavity Walls of the L483 Protostellar Envelope .  The Astrophysical Journal833 ( 55 ) 19pp   2016年12月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Physics  

    DOI: 10.3847/1538-4357/833/1/55

  • Hsi-Wei Yen, Patrick M. Koch, Hauyu Baobab Liu, Evaria Puspitaningrum, Naomi Hirano, Chin-Fei Lee, and Shigehisa Takakuwa .  Stacking Spectra in Protoplanetary Disks: Detecting Intensity Profiles from Hidden Molecular Lines in HD 163296 .  The Astrophysical Journal832 ( 204 ) 9pp   2016年12月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/0004-637X/832/2/204

    arXiv

  • Jeremy Lim, Tomoyuki Hanawa, Paul K. H. Yeung, Shigehisa Takakuwa, Tomoaki Matsumoto, and Kazuya Saigo .  Formation of the Unequal-mass Binary Protostars in L1551NE by Rotationally driven Fragmentation .  The Astrophysical Journal831 ( 90 ) 13pp   2016年11月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    DOI: 10.3847/0004-637X/831/1/90

    arXiv

  • Kitayama, T., Ueta, S., Takakuwa, S., et al. .  The Sunyaev-Zel'dovich effect at 5″: RX J1347.5-1145 imaged by ALMA .  Publications of the Astronomical Society of Japan68 ( 88 ) 19pp   2016年10月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本天文学会  

    We present the first image of the thermal Sunyaev-Zel'dovich effect (SZE) obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combining 7-m and 12-m arrays in Band 3, we create an SZE map toward a galaxy cluster RX J1347.5-1145 with 5″ resolution (corresponding to a physical size of 20 h-1 kpc), the highest angular and physical spatial resolutions achieved to-date for imaging the SZE, while retaining extended signals out to 40″. The 1 σ statistical sensitivity of the image is 0.017 mJy beam-1 or 0.12 mKCMB at the 5″ full width at half maximum. The SZE image shows a good agreement with an electron pressure map reconstructed independently from the X-ray data and offers a new probe of the small-scale structure of the intracluster medium. Our results demonstrate that ALMA is a powerful instrument for imaging the SZE in compact galaxy clusters with unprecedented angular resolution and sensitivity. As the first report on the detection of the SZE by ALMA, we present detailed analysis procedures including corrections for the missing flux, to provide guiding methods for analyzing and interpreting future SZE images obtained by ALMA.

    DOI: 10.1093/pasj/psw082

    arXiv

  • Lim, J., Yeung, P. K. H., Hanawa, T., Takakuwa, S., et al. .  Rotationally driven Fragmentation in the Formation of the Binary Protostellar System L1551 IRS 5 .  THE ASTROPHYSICAL JOURNAL826 ( 153 ) 20pp   2016年8月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    Both bulk rotation and local turbulence have been widely suggested to drive the fragmentation in collapsing cores that produces multiple star systems. Even when the two mechanisms predict different alignments for stellar spins and orbits, subsequent internal or external interactions can drive multiple systems toward or away from alignment, thus masking their formation processes. Here, we demonstrate that the geometrical and dynamical relationship between a binary system and its surrounding bulk envelope provide the crucial distinction between fragmentation models. We find that the circumstellar disks of the binary protostellar system L1551 IRS 5 are closely parallel, not just with each other but also with their surrounding flattened envelope. Measurements of the relative proper motion of the binary components spanning nearly 30 years indicate an orbital motion related to that of the envelope rotation. Eliminating orbital solutions whereby the circumstellar disks would be tidally truncated to sizes smaller than observed, the remaining solutions favor a circular or low-eccentricity orbit tilted by up to ˜25° from the circumstellar disks. Turbulence-driven fragmentation can generate local angular momentum to produce a coplanar binary system, but this would have no particular relationship to the system’s surrounding envelope. Instead, the observed properties conform with predictions for rotationally driven fragmentation. If the fragments were produced at different heights or on opposite sides of the mid-plane in the flattened central region of a rotating core, the resulting protostars would then exhibit circumstellar disks parallel with the surrounding envelope but tilted from the orbital plane, as is observed.

    DOI: 10.3847/0004-637X/826/2/153

    arXiv

  • Hsi-Wei Yen, Hauyu Baobab Liu, Pin-Gao Gu, Naomi Hirano, Chin-Fei Lee, Evaria Puspitaningrum, & Shigehisa Takakuwa .  Gas Gaps in the Protoplanetary Disk around the Young Protostar HL Tau .  THE ASTROPHYSICAL JOURNAL LETTERS820 ( L25 ) 7pp   2016年4月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    We have analyzed the HCO+ (1-0) data of the Class I-II protostar, HL Tau, obtained from the Atacama Large Millimeter/submillimeter Array long baseline campaign. We generated the HCO+ image cube at an angular resolution of ˜0.″07 (˜10 au) and performed azimuthal averaging on the image cube to enhance the signal-to-noise ratio and measure the radial profile of the HCO+ integrated intensity. Two gaps at radii of ˜28 and ˜69 au and a central cavity are identified in the radial intensity profile. The inner HCO+ gap is coincident with the millimeter continuum gap at a radius of 32 au. The outer HCO+ gap is located at the millimeter continuum bright ring at a radius of 69 au and overlaps with the two millimeter continuum gaps at radii of 64 and 74 au. On the contrary, the presence of the central cavity is likely due to the high optical depth of the 3 mm continuum emission and not the depletion of the HCO+ gas. We derived the HCO+ column density profile from its intensity profile. From the column density profile, the FWHM widths of the inner and outer HCO+ gaps are both estimated to be ˜14 au, and their depths are estimated to be ˜2.4 and ˜5.0. These results are consistent with the expectation from the gaps opened by forming (sub-)Jovian mass planets, while placing tight constraints on the theoretical models solely incorporating the variation of dust properties and grain sizes.

    DOI: 10.3847/2041-8205/820/2/L25

    arXiv

  • Hiroyuki HIRASHITA, Patrick M. KOCH, Satoki MATSUSHITA, Shigehisa TAKAKUWA, Masanori NAKAMURA, Keiichi ASADA, Hauyu Baobab LIU, Yuji URATA, Ming-Jye WANG, Wei-Hao WANG, Satoko TAKAHASHI, Ya-Wen TANG, Hsian-Hong CHANG, Kuiyun HUANG, Oscar MORATA, Masaaki OTSUKA, Kai-Yang LIN, An-Li TSAI, Yen-Ting LIN, Sundar SRINIVASAN, Pierre MARTIN -COCHER, Hung-Yi PU, Francisca KEMPER, Nimesh PATEL, Paul GRIMES, Yau-De HUANG, Chih-Chiang HAN, Yen-Ru HUANG, Hiroaki NISHIOKA, Lupin Chun-Che LIN, Qizhou ZHANG, Eric KETO, Roberto BURGOS, Ming-Tang CHEN, Makoto I NOUE, & Paul T. P. HO .  First-generation science cases for ground-based terahertz telescopes .  Publications of the Astronomical Society of Japan68 ( 1 ) 41pp   2016年2月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本天文学会  

    Ground-based observations at terahertz (THz) frequencies are a newly explorable area of astronomy in the coming decades. We discuss science cases for a first-generation 10-m class THz telescope, focusing on the Greenland Telescope as an example of such a facility. We propose science cases and provide quantitative estimates for each case. The largest advantage of ground-based THz telescopes is their higher angular resolution (˜ 4″ for a 10-m dish), as compared to space or airborne THz telescopes. Thus, high-resolution mapping is an important scientific argument. In particular, we can isolate zones of interest for Galactic and extragalactic star-forming regions. The THz windows are suitable for observations of high-excitation CO lines and [N II] 205-μm lines, which are scientifically relevant tracers of star formation and stellar feedback. Those lines are the brightest lines in the THz windows, so they are suitable for the initiation of ground-based THz observations. THz polarization of star-forming regions can also be explored since it traces the dust population contributing to the THz spectral peak. For survey-type observations, we focus on "sub-THz" extragalactic surveys, the uniqueness of which is detecting galaxies at redshifts z ˜ 1-2, where the dust emission per comoving volume is the largest in the history of the Universe. Finally we explore possibilities of flexible time scheduling, which enables us to monitor active galactic nuclei, and to target gamma-ray burst afterglows. For these objects, THz and submillimeter wavelength ranges have not yet been explored.

    DOI: 10.1093/pasj/psv115

    arXiv

  • Shigehisa Takakuwa, Kazuhiro Kiyokane, Kazuya Saigo, & Masao Saito .  Dispersing Envelope around the Keplerian Circumbinary Disk in L1551 NE and Its Implications for Binary Growth .  The Astrophysical Journal814 ( 160 ) 18pp   2015年12月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    We performed mapping observations of the Class I protostellar binary system L1551 NE in the C18O (J = 3-2), 13CO (J = 3-2), CS (J = 7-6), and SO (JN = 78-67) lines with the Atacama Submillimeter Telescope Experiment (ASTE). The ASTE C18O data were combined with our previous SMA C18O data, which show a r ˜ 300 AU scale Keplerian disk around the protostellar binary system. The C18O maps show a ˜20,000 AU scale protostellar envelope surrounding the central Keplerian circumbinary disk. The envelope exhibits a northeast (blue) to southwest (red) velocity gradient along the minor axis, which can be interpreted as a dispersing gas motion with an outward velocity of 0.3 km s-1, while no rotational motion in the envelope is seen. In addition to the envelope, two ≲4000 AU scale, high-velocity (≳1.3 km s-1) redshifted 13CO and CS emission components are found ˜40″ southwest and ˜20″ west of the protostellar binary. These redshifted components are most likely outflow components driven from the neighboring protostellar source L1551 IRS 5, and are colliding with the envelope in L1551 NE. The net momentum, kinetic, and internal energies of the L1551 IRS 5 outflow components are comparable to those of the L1551 NE envelope, and the interactions between the outflows and the envelope are likely to cause the dissipation of the envelope and thus suppression of further growth of the mass and mass ratio of the central protostellar binary in L1551 NE.

    DOI: 10.1088/0004-637X/814/2/160

    arXiv

  • Shigehisa Takakuwa, Masao Saito, Kazuya Saigo, Tomoaki Matsumoto, Jeremy Lim, Tomoyuki Hanawa, & Paul T. P. Ho .  Angular Momentum Exchange by Gravitational Torques and Infall in the Circumbinary Disk of the Protostellar System L1551 NE .  The Astrophysical Journal796 ( 1 ) 17pp   2014年11月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    We report an ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C18O (3-2), and 13CO (3-2) lines at a ~1.6 times higher resolution and a ~6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ~ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary system are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.

    DOI: 10.1088/0004-637X/796/1/1

    arXiv

  • Takakuwa, S., Saito, M., Lim, J., & Saigo, K. .  Evidence for Infalling Gas of Low Angular Momentum toward the L1551 NE Keplerian Circumbinary Disk .  The Astrophysical Journal776 ( 51 ) 11pp   2013年10月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We report follow-up C18O(3-2) line observations of the Class I binary protostellar system L1551 NE with the Submillimeter Array in its compact and subcompact configurations. Our previous observations at a higher angular resolution in the extended configuration revealed a circumbinary disk exhibiting Keplerian motion. The combined data, with more extensive spatial coverage (~140-2000 AU), verify the presence of a Keplerian circumbinary disk and reveal for the first time a distinct low-velocity (lsim ± 0.5 km s-1 from the systemic velocity) component that displays a velocity gradient along the minor axis of the circumbinary disk. Our simple model that reproduces the main features seen in the position-velocity diagrams comprises a circumbinary disk exhibiting Keplerian motion out to a radius of ~300 AU, beyond which the gas exhibits pure infall at a constant velocity of ~0.6 km s-1. This velocity is significantly smaller than the expected free-fall velocity of ~2.2 km s-1 onto the L1551 NE protostellar mass of ~0.8 M ⊙ at ~300 AU, suggesting that the infalling gas is decelerated as it moves into regions of high gas pressure in the circumbinary disk. The discontinuity in angular momenta between the outer infalling gas and the inner Keplerian circumbinary disk implies an abrupt transition in the effectiveness at which magnetic braking is able to transfer angular momentum outward, a result perhaps of the different plasma β values and the ionization fractions between the outer and inner regions of the circumbinary disk.

    DOI: 10.1088/0004-637X/776/1/51

    arXiv

  • Takakuwa, S., Saito, M., Lim, J., Saigo, K., Sridharan, T. K., & Patel, N. A. .  A Keplerian Circumbinary Disk around the Protostellar System L1551 NE .  The Astrophysical Journal754 ( 52 ) 12pp   2012年7月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We present Submillimeter Array observations of a Keplerian disk around the Class I protobinary system L1551 NE in 335 GHz continuum emission and submillimeter line emission in 13CO (J = 3-2) and C18O (J = 3-2) at a resolution of ~120 × 80 AU. The 335 GHz dust-continuum image shows a strong central peak closely coincident with the binary protostars and likely corresponding to circumstellar disks, surrounded by a ~600 × 300 AU feature elongated approximately perpendicular to the [Fe II] jet from the southern protostellar component suggestive of a circumbinary disk. The 13CO and C18O images confirm that the circumbinary continuum feature is indeed a rotating disk; furthermore, the C18O channel maps can be well modeled by a geometrically thin disk exhibiting Keplerian rotation. We estimate a mass for the circumbinary disk of ~0.03-0.12 M ⊙, compared with an enclosed mass of ~0.8 M ⊙ that is dominated by the protobinary system. Compared with several other Class I protostars known to exhibit Keplerian disks, L1551 NE has the lowest bolometric temperature (~91 K), highest envelope mass (~0.39 M ⊙), and the lowest ratio in stellar mass to envelope + disk + stellar mass (~0.65). L1551 NE may therefore be the youngest protostellar object so far found to exhibit a Keplerian disk. Our observations present firm evidence that Keplerian disks around binary protostellar systems, "Keplerian circumbinary disks," can exist. We speculate that tidal effects from binary companions could transport angular momenta toward the inner edge of the circumbinary disk and create the Keplerian circumbinary disk.

    DOI: 10.1088/0004-637X/754/1/52

    arXiv

  • Takakuwa, S., & Kamazaki, T. .  Skewed Distributions and Opposite Velocity Gradients of Submillimeter Molecular Lines in Low-Mass Protostellar Envelopes .  Publications of the Astronomical Society of Japan63 ( 4 ) 921 - 939   2011年8月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本天文学会  

    We have made mapping observations of L 1551 IRS 5, L 1551 NE, L 723, and L 43 and single-point observations of IRAS 16293-2422 in the submillimeter CS (J ="> 7-6) and HCN (J = ;4-3) lines with Atacama Submillimeter Telescope Experiment (ASTE). Using the present data and our previous ASTE observations of L 483 and B 335 together, we found a definite correlation between source bolometric luminosities and total integrated intensities of the submillimeter lines (ICS ∝ Lbol0.92). The combined ASTE + Submillimeter Array CS (7-6) image of L 1551 IRS 5 exhibits an extended (˜2000 AU) component tracing the associated reflection nebula at west and southwest, as well as a compact (≲ 500 AU) component centered on the protostellar position. The peaks of the CS and HCN emissions in L 1551 NE are not located at the protostellar position but offset (˜1400 AU) toward the associated reflection nebula at west. By statistical analyses, we confirmed the velocity gradients of the CS (7-6) emission that are opposite to those of the millimeter lines along the outflow direction, which we reported in our early paper. The magnitudes of the submillimeter velocity gradients are estimated to be (9.7±1.7) × 10-3 km s-1 arcsec-1 in L 1551 IRS 5 and (7.6±2.4) × 10-3 km s-1 arcsec-1 in L 483. We suggest that the ``skewed' submillimeter molecular emissions toward the associated reflection nebulae at a few thousand AU scale trace the warm (≳ 40 K) walls of the envelope cavities, excavated by the associated outflows and directly irradiated by the central protostars. The opposite velocity gradients along the outflow direction likely reflect the dispersing gas motion at the wall of the cavity in envelopes perpendicular to the outflow.

    DOI: 10.1093/pasj/63.4.921

    arXiv

  • Takakuwa, S., Ohashi, N., & Aikawa, Y. .  Carbon-chain and Organic Molecules Around Very Low Luminosity Protostellar Objects of L1521F-IRS and IRAM 04191+1522 .  The Astrophysical Journal728 ( 101 ) 10pp   2011年2月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We have observed dense gas around the Very Low Luminosity Objects (VeLLOs) L1521F-IRS and IRAM 04191+1522 in carbon-chain and organic molecular lines with the Nobeyama 45 m telescope. Toward L1521F-IRS, carbon-chain lines of CH3CCH (50-40), C4H ({17/2}-{15/2}), and C3H2 (212-101) are 1.5-3.5 times stronger than those toward IRAM 04191+1522, and the abundances of the carbon-chain molecules toward L1521F-IRS are 2-5 times higher than those toward IRAM 04191+1522. Mapping observations of these carbon-chain molecular lines show that in L1521F the peak positions of these carbon-chain molecular lines are different from each other and there is no emission peak toward the VeLLO position, while in IRAM 04191+1522 these carbon-chain lines are as weak as the detection limits, except for the C3H2 line. The observed chemical differentiation between L1521F and IRAM 04191+1522 suggests that the evolutionary stage of L1521F-IRS is younger than that of IRAM 04191+1522, consistent with the extent of the associated outflows seen in the 13CO (1-0) line. The non-detection of the organic molecular lines of CH3OH (6-2-7-1 E) and CH3CN (60-50) implies that the warm (~100 K) molecular-desorbing region heated by the central protostar is smaller than ~100 AU toward L1521F-IRS and IRAM 04191+1522, suggesting the young age of these VeLLOs. We propose that the chemical status of surrounding dense gas can be used to trace the evolutionary stages of VeLLOs.

    DOI: 10.1088/0004-637X/728/2/101

    arXiv

  • Takakuwa, S., Iono, D., Vila-Vilaro, B., Sekiguchi, T., & Kawabe, R. .  Scientific role of ACA for low-mass star-formation study .  Astrophysics and Space Science313 ( 1-3 ) 169 - 173   2008年1月査読

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPRINGER  

    We discuss the scientific role of the Atacama Compact Array (ACA), the Japanese contribution to the ALMA project, for low-mass star-formation study. Our recent observations of several low-mass protostellar envelopes in the submillimeter CS ( J=7 6) and HCN ( J=4 3) lines with the SMA and ASTE have revealed that these submillimeter emissions are more extended than ˜2000 AU and show different velocity structures from those traced by millimeter lines. These results suggest the importance of taking short-spacing informations the ACA can offer. Our comprehensive imaging simulations of these protostellar envelopes, as well as prestellar cores and debris disks, unprecedentedly demonstrate the scientific importance of ACA.

    DOI: 10.1007/s10509-007-9617-2

  • Takakuwa, S., Ohashi, N., Bourke, T. L., et al. .  Arcsecond-Resolution Submillimeter HCN Imaging of the Binary Protostar IRAS 16293-2422 .  The Astrophysical Journal662 ( 1 ) 431 - 442   2007年6月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    With the Submillimeter Array (SMA) we have made high angular resolution (~1''=160 AU) observations of the protobinary system IRAS 16293-2422 in the HCN (4-3), HC15N (4-3), and 354.5 GHz continuum emission. The HCN (4-3) line was also observed using the JCMT to supply missing short-spacing information. The submillimeter continuum emission is detected from the individual binary components of source A in the southeast and source B in the northwest, with a separation of ~5". The optically thin HC15N (4-3) emission taken with the SMA has revealed a compact (~500 AU) flattened structure (P.A.=-16deg) at source A. This compact structure shows a velocity gradient along the projected minor axis, which can be interpreted as an infalling gas motion. Our HCN image including the short-spacing information shows an extended (~3000 AU) circumbinary envelope, as well as the compact structure at source A. A toy model consisting of a flattened structure with radial infall toward a 1 Msolar central star reproduces the HCN/HC15N position-velocity diagram along the minor axis of the HC15N emission. In the extended envelope there is also a northeast (blue) to southwest (red) velocity gradient across the binary alignment, which is likely to reflect gas motion in the swept-up dense gas associated with the molecular outflow from source A. Only a weak and narrow (~2 km s-1) compact HC15N emission is associated with source B, where no clear molecular outflow is identified, suggesting the different evolutionary starges between sources A and B. Our study demonstrates the importance of adding short-spacing data to interferometer data in order to probe the detailed structure and kinematics of low-mass protostellar envelopes.

    DOI: 10.1086/513589

    arXiv

  • Takakuwa, S., Kamazaki, T., Saito, M., Yamaguchi, N., & Kohno, K. .  ASTE Observations of Warm Gas in Low-Mass Protostellar Envelopes: Different Kinematics between Submillimeter and Millimeter Lines .  Publications of the Astronomical Society of Japan59 ( 1 ) 1 - 13   2007年2月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本天文学会  

    With the ASTE telescope, we have observed three low-mass protostellar envelopes around L483, B335, and L723 in the submillimeter CS (J = 7-6) and HCN (J = 4-3) lines. We detected both the CS and HCN lines toward all targets, and the typical CS intensity (˜ 1.0 K in TB) was twice higher than that of the HCN line. Mapping observations of L483 in these lines have shown that the submillimeter emissions are resolved, exhibit a western extension from the central protostar, and that the deconvolved size is ˜ 5500 AU × 3700 AU (PA = 78°) in the HCN emission. The extent of the submillimeter emission in L483 implies the presence of higher temperature (/gtrsim 40 K) gas at 4000 AU away from the central protostar, which suggests that we need to take 2-dimensional radiative transfer models with a bipolar cavity into account. The position-velocity diagrams of these submillimeter lines along the axis of the associated molecular outflow exhibit that the sense of the submillimeter velocity gradient is opposite to that of the millimeter observation or the associated molecular outflow, both in L483 and in B335. We suggest that expanding gas motions at the surface of the flattened envelope, which is irradiated by the central protostar directly, are the origin of the observed submillimeter velocity structure.

    DOI: 10.1093/pasj/59.1.1

    arXiv

  • Takakuwa, S., Ohashi, N., Ho, P. T. P., et al. .  Submillimeter Array Observations of L1551 IRS 5 in CS J = 7-6 .  The Astrophysical Journal Letters616 ( 1 ) L15 - L18   2004年11月査読

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    We have imaged the circumstellar envelope around the binary protostar L1551 IRS 5 in CS J=7-6 and 343 GHz continuum emission at ~3" resolution using the Submillimeter Array. The continuum emission shows an elongated structure (~220×100 AU) around the binary perpendicular to the axis of the associated radio jet. The CS emission extends over ~400 AU, appears approximately circularly symmetric, and shows a velocity gradient from southeast (blueshifted) to northwest (redshifted). The direction of the velocity gradient is different from that observed in C18O J=1-0. This may be because rotation is more dominant in the CS envelope than the C18O envelope, in which both infall and rotation exist. The CS emission can be divided into two velocity components: (1) a ``high'-velocity disklike structure surrounding the protostar +/-1.0-1.5 km s-1 from the systemic velocity, and (2) a ``low'-velocity structure located southwest of the protostar less than 1.0 km s-1 from the systemic velocity. The high-velocity component traces warm and dense gas with kinematics consistent with rotation around the protostar. The low-velocity component may arise from dense gas entrained in the outflow. Alternatively, this component may trace infalling and rotating gas in an envelope with a vertical structure.

    DOI: 10.1086/421939

    arXiv

  • Takakuwa, S., Ohashi, N., & Hirano, N. .  Interaction between the Outflow and the Core in IRAM 04191+1522 .  The Astrophysical Journal590 ( 2 ) 932 - 943   2003年6月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The American Astronomical Society  

    We have carried out mapping observations of the molecular core associated with the young Class 0 protostar, IRAM 04191+1522, in the CH3OH (JK=2K-1K) and C34S (J=2-1) lines, using the 45 m telescope at Nobeyama Radio Observatory. Our observations have revealed that there is a condensation associated with the protostar, elongated in the east-west direction mostly perpendicular to the axis of the associated CO outflow. Its size and mass are estimated to be 0.07×0.04 pc and 2.3 Msolar, respectively, from the CH3OH data. In addition to the elongated envelope, two compact (~0.03 pc) condensations were found in the CH3OH line at the southern edge of the elongated envelope, where the blueshifted CO outflow emerging from the protostar is located. In contrast to the elongated envelope, those compact CH3OH condensations show much larger line width (up to 2.0 km s-1), with centroid velocities blueshifted by ~0.8 km s-1. The compact condensations have momenta (~0.06 Msolar km s-1) comparable to that of the blueshifted molecular outflow. In addition, they are gravitationally unbound, and most probably will dissipate eventually. These results suggest that the compact condensations are probably formed in the course of interaction between the outflow and the ambient gas surrounding the protostar and that such interaction may cause dissipation of a part of the ambient gas. No drastic, localized enhancement of the CH3OH abundance is, however, observed toward the compact condensations, implying that there seems to be no significant shock heating at the compact condensations, in spite of the interaction with the outflow. This may be because the CO outflow velocity (<10 km s-1) is too low to cause effective heating to release CH3OH on dust grains into the gas phase.

    DOI: 10.1086/375190

    arXiv

  • Takakuwa, S., Kamazaki, T., Saito, M., & Hirano, N. .  H13CO+ and CH3OH Line Observations of Prestellar Dense Cores in the TMC-1C Region. II. Internal Structure .  The Astrophysical Journal584 ( 2 ) 818 - 831   2003年2月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We have carried out detailed H13CO+ (J=1-0) and CH3OH (JK=20-10 A+) observations of two dense cores in the TMC-1C region with the 45 m telescope at Nobeyama Radio Observatory and the Nobeyama Millimeter Array (NMA). These two cores, H13CO+ core 2 and CH3OH core 6, were identified previously by the H13CO+ and CH3OH mapping observations of the entire TMC-1C region and show no sign of protostar formation. We found that the internal structure of H13CO+ core 2 is different from that of cores with class 0 protostars; this core consists of three velocity components and shows the radial column density distribution of ~r-0.43+/-0.08, which is flatter than that in the protostellar cores (~r-1.0). The internal structure of CH3OH core 6 is different from that of H13CO+ core 2; the combined images of the 45 m and NMA data have revealed that there are three smaller scale CH3OH ``clumps'' ~2500 AU in size inside this core. The mass of the small-scale clumps, ~0.02 Msolar, is much smaller than the virial mass (~0.3 Msolar), suggesting that these clumps are gravitationally unbound. The velocity dispersion observed in these small-scale clumps is 0.45-0.5 km s-1, which is comparable to that of clumps with 0.02-0.03 pc in radius. A comparison of the velocity dispersion of the small-scale clumps and that of larger scale cores suggests that the velocity dispersion that follows the power law in the radius larger than ~0.02-0.03 pc turns into a constant value of ~0.45-0.5 km s-1 in the smaller size scale. The mass-size relation of the prestellar gas structures suggests that they follow the trend of constant gas density (~105 cm-3) in the radius from 0.006 to ~0.3 pc and that the smaller scale structures tend to be gravitationally unbound. The presence of the small clumps with substellar masses in prestellar cores implies that coalescence processes are likely to play an important role in forming protostars inside the cores. The observational difference of the internal structures among CH3OH core 6, H13CO+ core 2, and protostellar cores might represent the difference of the evolutionary stages.

    DOI: 10.1086/345845

  • Takakuwa, S., Kawaguchi, K., Mikami, H., & Saito, M. .  The Ortho-to-Para Ratio and the Chemical Properties of C3 H2 in Dark Cloud Cores .  Publications of the Astronomical Society of Japan53 ( 2 ) 251 - 257   2001年4月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:日本天文学会  

    We have observed cyclic C3H2 (JKaKc = 212-101, 202 - 111, 312 - 303) lines at the 3 mm wavelength region toward the starless TMC-1C cloud and the protostellar core of L 1527 with the 45 m telescope at Nobeyama Radio Observatory. In both clouds, the 212-101 and 202 - 111 lines are strongly detected, while the 312 - 303 line is only detected toward the center of the protostellar core L 1527. From our statistical equilibrium analyses of the ortho-C3H2(212-101) and the para-C3H2(202-111)lines, the ortho-to-para ratios of C3H2 are determined to be 2.4 +/- 0.1 and 2.5 +/- 0.5 in TMC-1C and L 1527, respectively. These values are lower than the statistical value of 3, although the error of the ratio in L 1527 is large. Since thermal equilibrium with a dust temperature of 10 K still gives a ratio of 3 in c-C3H2, this result should suggest the lower ortho-to-para ratio of the precursor molecule, c-C3H+3, which is thought to be mainly produced by C3H++H2. Thus, we conclude that the lower ortho-to-para ratio of c-C3H2 is due to a lower ortho-to-para ratio of H2 than the statistical value.

    DOI: 10.1093/pasj/53.2.251

  • Takakuwa, S., Mikami, H., Saito, M., & Hirano, N. .  A Comparison of the Spatial Distribution of H13CO+, CH3OH, and C34S Emission and Its Implication in Heiles Cloud 2 .  The Astrophysical Journal542 ( 1 ) 367 - 379   2000年10月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We have mapped the Heiles cloud 2 region in the Taurus molecular cloud complex with H13CO+ (J=1-0), CH3OH (JK=20-10 A+), and C34S (J=2-1) lines. Dense gas traced by the mapped lines with critical densities higher than 104 cm-3 is concentrated in four condensations, that is, the TMC 1 and TMC 1C filaments, L1527, and TMC 1A. We have found that the three emission lines have remarkably different spatial distributions. The H13CO+ emission traces well dense cores harboring protostars, while the CH3OH emission is weak toward the protostars and is rather enhanced toward cores without protostars. We found that there are two starless cores with enhanced CH3OH emission at the northwestern ends of the TMC 1 and TMC 1C filaments, toward which the H13CO+ emission is barely seen. On the basis of the analyses using the large velocity gradient (LVG) model, we show that the CH3OH abundance relative to H13CO+ is enhanced by up to 1 order of magnitude in the cores without protostars. The C34S abundance relative to H13CO+ also shows a similar trend to that of CH3OH. Such an abundance variation between H13CO+ and CH3OH and C34S can be explained in the scheme of time-dependent gas-phase chemical evolution, which predicts that CH3OH and C34S are abundant in the early stages of chemical evolution and become deficient in the later stages. A comparison of the spatial-velocity structures in TMC 1 observed with the three molecular lines suggests that this cloud consists of multiple components with different velocities and different chemical compositions along the line of sight.

    DOI: 10.1086/309505

  • Takakuwa, S., Mikami, H., & Saito, M. .  H13CO+ and CH3OH Line Observations of Prestellar Dense Cores in the TMC-1C Region .  The Astrophysical Journal501 ( 2 ) 723 - 730   1998年7月査読

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Astronomical Society  

    We have mapped the entire TMC-1C region in the H13CO+ (J = 1-0) and CH3OH (JK = 20-10A+) lines at a grid spacing of 50" with the 45 m telescope at Nobeyama Radio Observatory. We have also conducted high spatial resolution mapping observations of the TMC-1C region at a grid spacing of 34" in both lines toward a 6' × 6' portion in the south and a 4' × 4' portion in the north. We found that the structure of TMC-1C is filamentary in both molecular lines. The size and position angle of the filament are 0.75 pc × 0.17 pc and 135°, respectively. The filament consists of dense (~105 cm-3) cores which are traced by either H13CO+ or CH3OH lines. We found that the distribution of cores seen in H13CO+ is quite different from the distribution of cores seen in CH3OH. The large velocity gradient analyses indicate that this difference is a result of the relative abundance variation between H13CO+ and CH3OH in the cores by about 1 order of magnitude. We have also carried out multitransitional observations of C3H2 (JK',K'' = 21,2-10,1 and 31,2-30,3) at two positions in the same cloud in order to estimate the molecular hydrogen densities for H13CO+ and CH3OH cores and found that the densities are around 105 cm-3 for both cores. These starless cores (no IRAS source), considered to be prestellar cores, seem to be at chemically different evolutionary stages; the H13CO+ cores are more evolved and closer to protostar formation than CH3OH cores. On the other hand, we found no difference in physical properties, i.e., the size, line width, and mass, between H13CO+ and CH3OH cores; the averages are about 0.07 pc, 0.3 km s-1, and 2 M⊙, respectively.

    DOI: 10.1086/305855

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MISC

  • ALMA観測により見えてきた双子の太陽の誕生秘話

    高桑繁久

    パリティ   31 ( 1 )   60 - 61   2016年1月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(商業誌、新聞、ウェブメディア)   出版者・発行元:丸善出版  

  • サブミリ波天文学最前線-SMA, ASTEそしてALMAによる原始星星周エンベロープのサブミリ波分子輝線観測-

    高桑 繁久

    天文月報   100 ( 7 )   330 - 339   2007年7月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:日本天文学会  

  • 若い原始星 IRAM 04191+1522 における分子雲コアとアウトフローの相互作用

    高桑 繁久

    天文月報   96 ( 8 )   421 - 427   2003年8月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:日本天文学会  

  • 分子雲コアの化学進化と星形成 -分子輝線の分布は何を表しているのか?-

    高桑 繁久

    天文月報   93 ( 10 )   616 - 625   2000年10月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:日本天文学会  

共同研究・競争的資金等の研究

  • Planet Formation in Protostellar Disks: eDisk and Beyond 国際共著

    2023年2月 - 2026年1月

    自然科学研究機構国立天文台  ALMA共同科学研究事業 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:18000000円

  • ALMA大型観測プログラムによる原始星円盤における惑星形成の解明 国際共著

    2021年4月 - 2025年3月

    独立行政法人日本学術振興会  科学研究費補助金  基盤研究(A)(一般)

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:20100000円

  • 星と惑星形成の多様性を繋ぐ基礎研究 国際共著

    2021年4月 - 2023年3月

    独立行政法人日本学術振興会  科学研究費補助金  新学術領域研究(研究領域提案型)

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:4030000円 ( 直接経費:3100000円 、 間接経費:930000円 )

  • Early Planet Formation in Embedded Disks 国際共著

    2019年12月

    自然科学研究機構国立天文台  ALMA Workshop 2019a (Large Proposal) 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:950000円

  • ALMA Long Baseline 観測による原始惑星の直接撮像 国際共著

    2018年4月 - 2021年3月

    独立行政法人日本学術振興会  科学研究費補助金  基盤研究(C)

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    担当区分:研究代表者  資金種別:競争的資金

    本研究は、アタカマ大型ミリ波サブミリ波干渉計 (ALMA) の観測により、形成途上の惑星「原始惑星」を直接撮像することを目 的とする。これまでのALMAの観測により、誕生から1千万年程度経った若い星 (Class II, III天体) の周囲において原始惑星の 探査が精力的に行われてきたが、その直接撮像には至っていない。本研究では、Class II, III よりさらに若い (百万年以下) 進化段階にある原始星 (Class 0-I) において高解像度のALMA 観測を行い、原始惑星の直接撮像を目指す。もし既存のALMAの観 測で原始惑星の直接検出に至らなかった場合には、原始惑星の観測の観点からALMAの次期拡張計画である「ALMA Long Baseline (超長基線)」計画に必要なスペックを提示し、科学的側面から本拡張計画をリードできるようにしていく。

  • ALMA による原始星周囲の円盤の形成過程の解明 国際共著

    2018年2月 - 2020年1月

    自然科学研究機構国立天文台  ALMA共同科学研究事業 

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    担当区分:研究代表者  資金種別:競争的資金

    本研究では、原始星周囲で、惑星系形成の現場である円盤「原始惑星系円盤」がどのように形成されていくのかを明らかにすることを目的とする。ALMA Large Program も含めた我々のグループの ALMA 観測、および ALMA アーカイブデータにより、Class 0 前期から Class I 後期に至るまでの原始星の周囲の分子ガスの構造、 運動を~20 au から~10000 au スケールに至るまで調べる。また、円盤形成に重要な影響を及ぼすと考えられている磁場の構造、強度の観測も ALMA により併せて行う。 これにより、原始星周囲の物質がどのように降り積もり回転円盤を構築していくの か、さらにその円盤でどのようにして惑星が形作られていくのかを明らかにしていく。

  • ALMA望遠鏡による連星の形成過程の解明 国際共著

    2016年9月 - 2018年3月

    独立行政法人日本学術振興会  科学研究費補助金  研究活動スタート支援

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    担当区分:研究代表者  資金種別:競争的資金

    本研究は、ふたつの星が互いの周りをまわっている双子の星「連星」がどのように形成されているのかを明らかにすることを目的とする。太陽質量程度の星の過半数は連星であることがわかっているが、単一の星の形成過程と比べ、連星の形成過程は観測の解像度、感度の制限によりよくわかっていなかった。本研究では、まもなく本稼働を始める究極のミリ波、サブミリ波電波望遠鏡、アタカマ大型ミリ波サブミリ波干渉計(Atacama Large Millimeter/submillimeter Array: ALMA)を用いて、形成中の連星「原始星連星」周囲のガス円盤「周連星系円盤」の構造、運動の詳細観測を行う。質量や質量比が異なる10天体あまりの原始星連星をALMA望遠鏡により系統的に観測し、その結果を我々の理論モデルと比較することにより、周連星系円盤の物質がどのように原始星連星に降り積もり、連星の質量や質量比を決めているのかを明らかにする。

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メディア報道

  • 惑星はいつ誕生するのか〜最初期段階を捉える 新聞・雑誌

    鹿児島讀賣テレビ ニュース every   日本経済新聞朝刊  サイエンスフロンティア面  2023年7月

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    執筆者:本人 

  • 惑星ができる過程、解明へ一歩 鹿大院チーム 連星の動き分析 新聞・雑誌

    南日本新聞社  南日本新聞  3面  2021年10月

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    執筆者:本人以外