<@IF:>検索詳細｜<@ENDIF>MF大学 (2024)

The candidates of long-periodic variable sources in 6.7 GHz methanol masers associated with four high-mass star-forming regions　　　　　　　　　　　　　　　
Yoshihiro TANABE and Yoshinori YONEKURA
Publ. Astron. Soc. Japan, Dec. 2024, [Reviewed]

An Ultra wide-band, high-sensitivity Q-band receiver for single-dish telescopes, eQ:,rest frequency determination of CCS (JN=43-32) and SO (JN=10-01), and high-redshift CO (J=1-0) detection　　　　　　　　　　　　　　　
Fumitaka Nakamura; Chau-Ching Chiong; Kotomi Taniguchi; Chen Chien; Chin-Ting Ho; Yuh-Jing Hwang; You-Ting Yeh; Tomomi Shimoikura; Yasumasa Yamasaki; Sheng-Yuan Liu; Naomi Hirano; Shih-Ping Lai; Atsushi Nishimura; Ryohei Kawabe; Kazuhito Dobashi; Yasunori Fujii; Yoshinori Yonekura; and Hideo Ogawa
Publ. Astron. Soc. Japan, Dec. 2024, [Reviewed]

Limits of water maser kinematics: insights from the high-mass protostar AFGL 5142-MM1
Zulfazli Rosli; Ross A. Burns; Affan Adly Nazri; Koichiro Sugiyama; Tomoya Hirota; Kee-Tae Kim; Yoshinori Yonekura; Liu Tie; Gabor Orosz; James Okwe Chibueze; Andrey M. Sobolev; Ji Hyun Kang; Chang Won Lee; Jihye Hwang; Hafieduddin Mohammad; Norsiah Hashim and Zamri Zainal Abidin
Monthly Notices of the Royal Astronomical Society, Feb. 2024, [Reviewed]

Precessing jet nozzle connecting to a spinning black hole in M87
Yuzhu Cui; Kazuhiro Hada; Tomohisa Kawashima; Motoki Kino; Weikang Lin; Yosuke Mizuno; Hyunwook Ro; Mareki Honma; Kunwoo Yi; Jintao Yu; Jongho Park; Wu Jiang; Zhiqiang Shen; Evgeniya Kravchenko; Juan-Carlos Algaba; Xiaopeng Cheng; Ilje Cho; Gabriele Giovannini; Marcello Giroletti; Taehyun Jung; Ru-Sen Lu; Kotaro Niinuma; Junghwan Oh; Ken Ohsuga; Satoko Sawada-Satoh; Bong Won Sohn; Hiroyuki R. Takahashi; Mieko Takamura; Fumie Tazaki; Sascha Trippe; Kiyoaki Wajima; Kazunori Akiyama; Tao An; Keiichi Asada; Salvatore Buttaccio; Do-Young Byun; Lang Cui; Yoshiaki Hagiwara; Tomoya Hirota; Jeffrey Hodgson; Noriyuki Kawaguchi; Jae-Young Kim; Sang-Sung Lee; Jee Won Lee; Jeong Ae Lee; Giuseppe Maccaferri; Andrea Melis; Alexey Melnikov; Carlo Migoni; Se-Jin Oh; Koichiro Sugiyama; Xuezheng Wang; Yingkang Zhang; Zhong Chen; Ju-Yeon Hwang; Dong-Kyu Jung; Hyo-Ryoung Kim; Jeong-Sook Kim; Hideyuki Kobayashi; Bin Li; Guanghui Li; Xiaofei Li; Zhiyong Liu; Qinghui Liu; Xiang Liu; Chung-Sik Oh; Tomoaki Oyama; Duk-Gyoo Roh; Jinqing Wang; Na Wang; Shiqiang Wang; Bo Xia; Hao Yan; Jae-Hwan Yeom; Yoshinori Yonekura; Jianping Yuan; Hua Zhang; Rongbing Zhao & Weiye Zhong, Springer Science and Business Media LLC
Nature, Sep. 2023, [Reviewed]

A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass protostar
R.A. Burns; Y. Uno; N. Sakai; J. Blanchard; Z. Fazil; G. Orosz; Y. Yonekura; Y. Tanabe; K. Sugiyama; T. Hirota; Kee-Tae Kim; A. Aberfelds; A.E. Volvach; A. Bartkiewicz; A. Caratti o Garatti; A.M. Sobolev; B. Stecklum; C. Brogan; C. Phillips; D.A. Ladeyschikov; D. Johnstone; G. Surcis; G.C. MacLeod; H. Linz; J.O. Chibueze; J. Brand; J. Eislöffel; L. Hyland; L. Uscanga; M. Olech; M. Durjasz; O. Bayandina; S. Breen; S.P. Ellingsen; S.P. van den Heever; T.R. Hunter; X. Chen
Nature Astronomy, May 2023, [Reviewed]

Super-Resolved Image of M87 Observed with East Asian VLBI Network
F. Tazaki; Y. Cui; K. Hada; M. Kino; I. Cho; G.-Y. Zhao; K. Akiyama; Y. Mizuno; H. Ro; M. Honma; R.-S. Lu; Z.-Q. Shen; L. Cui; Y. Yonekura, Obtaining high-resolution images at centimeter-or-longer wavelengths is vital for understanding the physics of jets. We reconstructed images from the M87 22 GHz data observed with the East Asian VLBI Network (EAVN) by using the regularized maximum likelihood (RML) method, which is different from the conventional imaging method CLEAN. Consequently, a bright core and jet extending about 30 mas to the northwest were detected with a higher resolution than in the CLEAN image. The width of the jet was 0.5 mas at 0.3 mas from the core, consistent with the width measured in the 86 GHz image in the previous study. In addition, three ridges were able to be detected at around 8 mas from the core, even though the peak-to-peak separation was only 1.0 mas. This indicates that the RML image's spatial resolution is at least 30% higher than that of the CLEAN image. This study is an important step for future multi-frequency and high-cadence observations of the EAVN to discuss the more detailed structure of the jet and its time variability., MDPI
Galaxies, Feb. 2023, [Reviewed]

Detection of a bright burst from the repeating FRB 20201124A at 2 GHz
S. Ikebe; K. Takefuji; T. Terasawa; S. Eie; T. Akahori; Y. Murata; T. Hashimoto; S. Kisaka; M. Honma; S. Yoshiura; S. Suzuki; T. Oyama; M. Sekido; K. Niinuma; H. Takeuchi; Y. Yonekura; T. Enoto
Publ. Astron. Soc. Japan, Feb. 2023, [Reviewed]

The Astrometric Animation of Water Masers towards the Mira Variable BX Cam
S. Xu; H. Imai; Y.J. Yun; B. Zhang; M.J. Rioja; R. Dodson; S.-H. Cho; J.H. Kim; L. Cui; A.M. Sobolev; J.O. Chibueze; D.-J. Kim; K. Amada; J. Nakashima; G. Orosz; M. Oyadomari; S. Oh; Y. Yonekura; Y. Sun; X. Mai; J. Zhang; S. Wen; T. Jung
Astrophys. J., Dec. 2022, [Reviewed]

Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)
K. Akiyama; J.-C. Algaba; T. An; K. Asada; K. Asanok; D.-Y. Byun; T. Chanapote; Z. Chen; W. Chen; X. Cheng; J.O. Chibueze; I. Cho; S.-H. Cho; H.-S. Chung; L. Cui; Y. Cui; A. Doi; J. Dong; K. Fujisawa; W. Gou; W. Guo; K. Hada; Y. Hagiwara; T. Hirota; J.A. Hodgson; M. Honma; H. Imai; P. Jaroenjittichai; W. Jiang; Y. Jiang; Y. Jiang; T. Jike; D.-K. Jung; T. Jung; N. Kawaguchi; D.-J. Kim; H.-R. Kim; J. Kim; J.-S. Kim; K.-T. Kim; S.-W. Kim; M. Kino; H. Kobayashi; S. Koyama; B.H. Kramer; J.-W. Lee; J.A. Lee; S.-S. Lee; S.W. Lee; B. Li; G. Li; X. Li; Z. Li; Q. Liu; X. Liu; R.-S. Lu; K. Motogi; M. Nakamura; K. Niinuma; C. Oh; H. Oh; J. Oh; S.-J. Oh; T. Oyama; J. Park; S. Poshyachinda; H. Ro; D.-G. Roh; W. Rujopakarn; N. Sakai; S. Sawada-Satoh; Z.-Q. Shen; K.M. Shibata; B.W. Sohn; B. Soonthornthum; K. Sugiyama; Y. Sun; M. Takamura; Y. Tanabe; F. Tazaki; S. Trippe; K. Wajima; J. Wang; N. Wang; S. Wang; X. Wang; B. Xia; S. Xu; H. Yan; W. Yang; J.-H. Yeom; K. Yi; S.-O. Yi; Y. Yonekura; H. Yoon; L. Yu; J. Yuan; Y. Yun; B. Zhang; H. Zhang; Y. Zhang; G.-Y. Zhao; R. Zhao; W. Zhong, The East Asian VLBI Network (EAVN) is an international VLBI facility in East Asia and is operated under mutual collaboration between East Asian countries, as well as part of Southeast Asian and European countries. EAVN currently consists of 16 radio telescopes and three correlators located in China, Japan, and Korea, and is operated mainly at three frequency bands, 6.7, 22, and 43 GHz with the longest baseline length of 5078 km, resulting in the highest angular resolution of 0.28 milliarcseconds at 43 GHz. One of distinct capabilities of EAVN is multi-frequency simultaneous data reception at nine telescopes, which enable us to employ the frequency phase transfer technique to obtain better sensitivity at higher observing frequencies. EAVN started its open-use program in the second half of 2018, providing a total observing time of more than 1100 h in a year. EAVN fills geographical gap in global VLBI array, resulting in enabling us to conduct contiguous high-resolution VLBI observations. EAVN has produced various scientific accomplishments especially in observations toward active galactic nuclei, evolved stars, and star-forming regions. These activities motivate us to initiate launch of the 'Global VLBI Alliance' to provide an opportunity of VLBI observation with the longest baselines on the earth., MDPI
Galaxies, Dec. 2022, [Reviewed]

The Yamaguchi Interferometer
K. Fujisawa; T. Aoki; S. Kanazawa; M. Akimoto; T. Ogura; K. Mori; K. Niinuma; K. Motogi; S. Sawada-Satoh; K. Takefuji; H. Ogawa; K. Kimura; Y. Yonekura; M. Honma
Publ. Astron. Soc. Japan, Dec. 2022, [Reviewed]

Two periods instead of one in a single 6.7 GHz methanol maser feature in G9.62+0.20E
G. C. MacLeod; Y. Yonekura; Y. Tanabe; W. A. Baan; C. L. Brogan; R. A. Burns; J. O. Chibueze; M. Houde; T. R. Hunter; S. E. Kurtz; F. Rajabi; D. P. Smits; B. Stecklum; and K. Sugiyama
Monthly Notices of the Royal Astronomical Society, Oct. 2022, [Reviewed]

Mid-Infrared and Maser Flux Variability Correlation in Massive Young Stellar Object G036.70+00.09
M. Uchiyama; K. Ichikawa; K. Sugiyama; Y. Tanabe and Y. Yonekura, We present the discovery of the simultaneous flux variation of a massive young stellar object (MYSO) G036.70+00.09 (G036.70) both in the maser emission and mid-infrared (MIR; lambda = 3-5 mu m) bands. Using the ALLWISE and NEOWISE archival databases that cover a long time span of approximately 10 yr with a cadence of 6 months, we confirm that G036.70 indicates a stochastic year-long MIR variability with no signs of a WISE band color change of W1 (3.4 mu m) -W2 (4.6 mu m). Cross-matching the MIR data set with the high-cadence 6.7 GHz class II methanol maser flux using the Hitachi 32 m radio telescope that discovered its periodicity in the methanol maser of 53.0-53.2 days, we also determine the flux correlations between the two bands at two different timescales, year-long and day-long, both of which have never been reported in MYSOs, except when they are in the accretion burst phase. The results of our study support the scenario that a class II methanol maser is pumped up by infrared emission from accreting disks of MYSOs. We also discuss the possible origins of MIR and maser variability. To explain the two observed phenomena, a stochastic year-long MIR variability with no signs of significant color change and maser-MIR variability correlation or a change in mass accretion rate and line-of-sight extinction because of the nonaxisymmetric dust density distribution in a rotating accretion disk are possible origins. Observations through spectroscopic monitoring of accretion-related emission lines are essential for determining the origin of the observed variability in G036.70., IOP Publishing Ltd
Astrophys. J., Sep. 2022, [Reviewed]

Extended Q-band (eQ) receiver for Nobeyama 45-m Telescope
Chau-Ching Chiong; Fumitaka Nakamura; Atsushi Nishimura; Ross A. Burns; Chen Chien; Kazuhito Dobashi; Yasunori Fujii; Chin-Ting Ho; Yau De Huang; Yuh-Jing Hwang; Shou-Ting Jian; Ryohei Kawabe; Kimihiro Kimura; Sheng-Yuan Liu; Shih-Ping Lai; Hideo Ogawa; Nozomi Okada; Seiji Kameno; Tomomi Shimoikura; Shigehisa Takakuwa; Kotomi Taniguchi; Wei-Hao Wang; You-Ting Yeh; Yasumasa Yamasaki; Yoshinori Yonekura, SPIE
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI, Aug. 2022

A multi-transition methanol maser study of the accretion burst source G358.93-0.03-MM1　　　　　　　　　　　　　　　
O.S. Bayandina; C.L. Brogan; R.A. Burns; X. Chen; T.R. Hunter; S.E. Kurtz; G.C. MacLeod; A.M. Sobolev; K. Sugiyama; I.E. Val’tts; and Y. Yonekura
Astron. J., Feb. 2022, [Reviewed]

Molecular line search toward the flaring 6.7-GHz methanol masers of G 24.33+0.13 and G 359.62–0.24: rare maser transitions detected　　　　　　　　　　　　　　　
T.P. McCarthy; G. Orosz; S.P. Ellingsen; S.L. Breen; M.A. Voronkov; R.A. Burns; M.Olech; Y. Yonekura; T. Hirota; P. Wolak; and L.J. Hyland
Monthly Notices of the Royal Astronomical Society, Jan. 2022, [Reviewed]

Measuring the impact of Indonesian antennas on global geodetic VLBI network
I. N. Huda; T. Hidayat; B. Dermawan; S. Lambert; N. Liu; S. Leon; K. Fujisawa; Y. Yonekura; K. Sugiyama; T. Hirota; P. W. Premadi; R. Breton; Y.-C. Minh; P. Jaroenjittichai; D. Wijaya; D. Pradipta; N. S. E. Putri; S. Ramadhan; L. Puspitarini; H. R. T. Wulandari and M. Hafieduddin, Springer Science and Business Media LLC
Exp. Astronomy, Oct. 2021, [Reviewed]

East Asian VLBI Network Observations of Active Galactic Nuclei Jets: Imaging with KaVA+Tianma+Nanshan
Y.-Z. Cui; K. Hada; M. Kino; B.-W. Sohn; J. Park; H.-W. Ro; S. Sawada-Satoh; W. Jiang; L. Cui; M. Honma; Z.-Q. Shen; F. Tazaki; T. An; I. Cho; G.-Y. Zhao; X.-P. Cheng; K. Niinuma; K. Wajima; Y.-K. Zhang; N. Kawaguchi; J.-C. Algaba; S. Koyama; T. Hirota; Y. Yonekura; N. Sakai; B. Xia; Y.-B. Jiang; L.-F. Yu; W. Gou; J.-Y. Hwang; Y.-C. Jiang; Y.-X. Sun; D.-K. Jung; H.-R. Kim; J.-S. Kim; H. Kobayashi; J.-W. Lee; J.-A. Lee; H. Zhang; G.-H. Li; Z.-Q. Xu; P. Li; J.-H. Oh; S.-J. Oh; C.-S. Oh; T. Oyama; D.-G. Roh; K.M. Shibata; W. Guo; R.-B. Zhao; W.-Y. Zhong; J.-Q. Wang; W.-J. Yang; H. Yan; J.-H. Yeom; B. Li; X.-F. Li; J.-P. Yuan; J. Dong; Z. Chen; K. Akiyama; K. Asada; D.-Y. Byun; Y. Hagiwara; J. Hodgson; T.-H. Jung; K.-T. Kim; S.-S. Lee; K. Yi; Q.-H. Liu; X. Liu; R.-S. Lu; M. Nakamura; S. Trippe; N. Wang; X.-Z. Wang; B. Zhang, IOP Publishing
Research in Astronomy and Astrophysics, Aug. 2021, [Reviewed]

Discovery of X-ray Enhancement Coinciding with Giant Radio Pulses from the Crab Pulsar
T. Enoto; T. Terasawa; S. Kisaka; C.-P. Hu; S. Guillot; N. Lewandowska; C. Malacaria; P.S. Ray; W.C.G. Ho; A.K. Harding; T. Okajima; Z. Arzoumanian; K.C. Gendreau; Z. Wadiasingh; C.B. Markwardt; Y. Soong; S. Kenyon; S. Bogdanov; W.A. Majid; T. Guver; G.K. Jaisawal; R. Foster; Y. Murata; H. Takeuchi; K. Takefuji; M. Sekido; Y. Yonekura; H. Misawa; F. Tsuchiya; T. Aoki; M. Tokumaru; M. Honma; O. Kameya; T. Oyama; K. Asano; S. Shibata and S.J. Tanaka, Giant radio pulses (GRPs) are sporadic bursts emitted by some pulsars that last a few microseconds and are hundreds to thousands of times brighter than regular pulses from these sources. The only GRP-associated emission outside of radio wavelengths is from the Crab Pulsar, where optical emission is enhanced by a few percentage points during GRPs. We observed the Crab Pulsar simultaneously at x-ray and radio wavelengths, finding enhancement of the x-ray emission by 3.8 ± 0.7% (a 5.4σ detection) coinciding with GRPs. This implies that the total emitted energy from GRPs is tens to hundreds of times higher than previously known. We discuss the implications for the pulsar emission mechanism and extragalactic fast radio bursts.
Science, Apr. 2021, [Reviewed]

Development of a 6.5-22.5 GHz very wide band feed antenna using a new Quadruple-Ridged Antenna for the traditional radio telescopes　　　　　　　　　　　　　　　
Y. Hasegawa; Y. Yamasaki; H. Ogawa; T. Kawakami; Y. Yonekura; K. Kimura; T. Akahori; M. Ishino; Y. Kawahara
IVS NICT Technology Development Center NEWS, Jan. 2021

A Search for Compact Radio Sources Toward the Center of the Galaxy　　　　　　　　　　　　　　　
Sachi Sukehiro; Kenta Fujisawa; and Yoshinori Yonekura
New Horizons in Galactic Center Astronomy and Beyond (eds. Masato Tsuboi and Tomoharu Oka), ASP Conference Series, Vol. 528, Proceedings of a workshop held 21-24 October 2019 at Keio University, Yokohama, Japan (San Francisco: Astronomical Society of the Pacific)., Jul. 2020

A heatwave of accretion energy traced by masers in the G358-MM1 high-mass protostar
R. A. Burns; K. Sugiyama; T. Hirota; Kee-Tae. Kim; A. M. Sobolev; B. Stecklum; G. C. MacLeod; Y. Yonekura; M. Olech; G. Orosz; S. P. Ellingsen; L. Hyland; A. Caratti o Garatti; C. Brogan; T. Hunter; C. Philips; S. P. van den Heever; J. Eislöffe; H. Linz; G. Surcis; J. O. Chibueze; W. Baan and B. Kramer
Nature Astronomy, Jan. 2020, [Reviewed]

VLBI at 230 GHz using SPART toward EHT and EAVN -hi-　　　　　　　　　　　　　　　
T. Aoki; H. Maezawa; S. Masui; D. Tsukiyama; A. Tomihara; N. Okada; A. Nishimura; H. Ogawa; K. Niinuma; R. Amari; T. Tsutsumi; K. Fujisawa; Y. Yonekura; Y. Kamichi; and M. Inoue
IVS NICT Technology Development Center NEWS, Dec. 2019

The VLBI survey of Extremely Compact HII regions associated with a high mass star just after nuclear ignition using Kashima - Hitachi baseline　　　　　　　　　　　　　　　
T. Ogura; K. Motogi; T. Aoki; K. Niinuma; K. Fujisawa; Y. Yonekura; M. Sekido; and K. Takefuji
IVS NICT Technology Development Center NEWS, Dec. 2019

Ten years of Ibaraki Station　　　　　　　　　　　　　　　
Y. Yonekura
IVS NICT Technology Development Center NEWS, Dec. 2019

Detection of new methanol maser transitions associated with G358.93-0.03
G. C. MacLeod; K. Sugiyama; T. R. Hunter; J. Quick; W. Baan; S. L. Breen; C. L. Brogan; R. A. Burns; X. Chen; J. O. Chibueze; M. Houde; J. F. Kaczmarek; H. Linz; F. Rajabi; Y. Saito; S. Schmidl; A. M. Sobolev; B. Stecklum; S. P. van den Heever; and Y. Yonekura
Monthly Notices of the Royal Astronomical Society, Nov. 2019, [Reviewed]

The Galactic Center Lobe Filled with Thermal Plasma
Halca NAGOSHI; Yuzo KUBOSE; Kenta FUJISAWA; Kazuo SORAI; Yoshinori YONEKURA; Koichiro SUGIYAMA; Kotaro NIINUMA; Kazuhito MOTOGI; and Takahiro AOKI
Publ. Astron. Soc. Japan, Aug. 2019, [Reviewed]

A balloon-borne very long baseline interferometry experiment in the stratosphere: Systems design and developments
Akihiro Doi; Yusuke Kono; Kimihiro Kimura; Satomi Nakahara; Tomoaki Oyama; Nozomi Okada; Yasutaka Satou; Kazuyoshi Yamash*ta; Naoko Matsumoto; Mitsuhisa Baba; Daisuke Yasuda; Shunsaku Suzuki; Yutaka Hasegawa; Mareki Honma; Hiroaki Tanaka; Kosei Ishimura; Yasuhiro Murata; Reiho Shimomukai; Tomohiro Tachi; Kazuya Saito; Naohiko Watanabe; Nobutaka Bando; Osamu Kameya; Yoshinori Yonekura; Mamoru Sekido; Yoshiyuki Inoue; Hiraku Sakamoto; Nozomu Kogiso; Yasuhiro Shoji; Hideo Ogawa; Kenta Fujisawa; Masanao Narita; Hiroshi Shibai; Hideyuki f*cke; Kenta Uehara; Shoko Koyama, Elsevier BV
Advances in Space Research, Jan. 2019, [Reviewed]

Performance evaluation of Usuda Deep Space Center 64 m antenna for radio astronomical observations and efforts on its improvement　　　　　　　　　　　　　　　
藏原 昂平; 中西 裕之; 村田 泰宏; 上原 顕太; 青木 貴弘; 今井 裕; 藤沢 健太; 米倉 覚則
Rep. Fac. Sci., Kagoshima Univ., Dec. 2018

A Face-on Accretion System in High Mass Star-Formation: Possible Dusty Infall Streams within 100 Astronomical Unit
K. Motogi; T. Hirota; K. Sorai; Y. Yonekura; K. Sugiyama; M. Honma; K. Niinuma; K. Hachisuka; K. Fujisawa; A.J. Walsh, We report on interferometric observations of a face-on accretion system around the High-Mass young stellar object, G353.273+0.641. The innermost accretion system of 100 au radius was resolved in a 45 GHz continuum image taken with the Jansky-Very Large Array. Our spectral energy distribution analysis indicated that the continuum could be explained by optically thick dust emission. The total mass of the dusty system is $\sim$ 0.2 $M_{\sun}$ at minimum and up to a few $M_{\sun}$ depending on the dust parameters. 6.7 GHz CH$_{3}$OH masers associated with the same system were also observed with the Australia Telescope Compact Array. The masers showed a spiral-like, non-axisymmetric distribution with a systematic velocity gradient. The line-of-sight velocity field is explained by an infall motion along a parabolic streamline that falls onto the equatorial plane of the face-on system. The streamline is quasi-radial and reaches the equatorial plane at a radius of 16 au. This is clearly smaller than that of typical accretion disks in High-Mass star formation, indicating that the initial angular momentum was very small, or the CH$_{3}$OH masers selectively trace accreting material that has small angular momentum. In the former case, the initial specific angular momentum is estimated to be 8 $\times$ 10$^{20}$ ($M_{*}$$/$10 $M_{\sun}$)$^{0.5}$ cm$^{2}$ s$^{-1}$, or a significant fraction of the initial angular momentum was removed outside of 100 au. The physical origin of such a streamline is still an open question and will be constrained by the higher-resolution ($\sim$ 10 mas) thermal continuum and line observations with ALMA long baselines.
Astrophysical Masers: Unlocking the Mysteries of the Universe, Proceedings of the International Astronomical Union, IAU Symposium, Volume 336, Aug. 2018

6.7 GHz Methanol Masers Observation with Phased Hitachi and Takahagi
K. Takefuji; K. Sugiyama; Y. Yonekura; T. Saito; K. Fujisawa; T. Kondo
Astrophysical Masers: Unlocking the Mysteries of the Universe, Proceedings of the International Astronomical Union, IAU Symposium, Volume 336, Aug. 2018

A comparative study of amplitude calibrations for the East Asia VLBI Network: A priori and template spectrum methods
Ilje Cho; Taehyun Jung; Guang-Yao Zhao; Kazunori Akiyama; Satoko Sawada-Satoh; Motoki Kino; Do-Young Byun; Bong Won Sohn; Katsunori M. Shibata; Tomoya Hirota; Kotaro Niinuma; Yoshinori Yonekura; Kenta Fujisawa; and Tomoaki Oyama, We present the results of comparative study of amplitude calibrations for East-Asia VLBI Network (EAVN) at 22 and 43 GHz using two different methods of an "a-priori" and a "template spectrum", particularly on lower declination sources. Using observational data sets of early EAVN observations, we investigated the elevation-dependence of the gain values at seven stations of the KaVA (KVN and VERA Array) and three additional telescopes in Japan (Takahagi 32m, Yamaguchi 32m and Nobeyama 45m). By comparing the independently obtained gain values based on these two methods, we found that the gain values from each method were consistent within 10% at elevations higher than 10 degree. We also found that the total flux densities of two images produced from the different amplitude calibrations were in agreement within 10% at both 22 and 43 GHz. By using the template spectrum method, furthermore, the additional radio telescopes can participate in the KaVA (i.e. EAVN) so that it can give a notable sensitivity increase. Therefore, our results will constrain the detailed conditions to reliably measure the VLBI amplitude using EAVN and give a potential to extend possible telescopes comprising EAVN.
Publ. Astron. Soc. Japan, Dec. 2017, [Reviewed]

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU　　　　　　　　　　　　　　　
Kazuhito Motogi; Tomoya Hirota; Kazuo Sorai; Yoshinori Yonekura; Koichiro Sugiyama; Mareki Honma; Kotaro Niinuma; Kazuya Hachisuka; Kenta Fujisawa; and Andrew J. Walsh
Astrophys. J., Nov. 2017, [Reviewed]

Development of the Phase-up Technology of the Radio Telescopes: 6.7 GHz Methanol Maser Observations with Phased Hitachi 32 m and Takahagi 32 m Radio Telescopes　　　　　　　　　　　　　　　
Kazuhiro Takefuji; Koichiro Sugiyama; Yoshinori Yonekura; Tagiru Saito; Kenta Fujisawa; Tetsuro Kondo
Publ. Astron. Soc. Pacific, Nov. 2017, [Reviewed]

OISTER Optical and Near-Infrared Monitoring Observations of a Peculiar Radio-Loud Active Galactic Nucleus SDSS J110006.07+442144.3
Tomoki Morokuma; Masaomi Tanaka; Yasuyuki T. Tanaka; Ryosuke Itoh; Nozomu Tominaga; Poshak Gandhi; Elena Pian; Paolo Mazzali; Kouji Ohta; Emiko Matsumoto; Takumi Shibata; Hinako Akimoto; Hiroshi Akitaya; Gamal B. Ali; Tsutomu Aoki; Mamoru Doi; Nana Ebisuda; Ahmed Essam; Kenta Fujisawa; Hideo f*ckushima; Shuhei Goda; Yuya Gouda; Hidekazu Hanayama; Yasuhito Hashiba; Osamu Hashimoto; Kenzo Hayashida; Yuichiro Hiratsuka; Satoshi Honda; Masataka Imai; Kanichiro Inoue; Michiko Ishibashi; Ikuru Iwata; Hideyuki Izumiura; Yuka Kanda; Miho Kawabata; Kenji Kawaguchi; Nobuyuki Kawai; Mitsuru Kokubo; Daisuke Kuroda; Hiroyuki Maehara; Hiroyuki Mito; Kazuma Mitsuda; Ryota Miyagawa; Takeshi Miyaji; Yusuke Miyamoto; Kumiko Morihana; Yuki Moritani; Kana Morokuma-Matsui; Kotone Murakami; Katsuhiro L. Murata; Takahiro Nagayama; Kazuki Nakamura; Tatsuya Nakaoka; Kotaro Niinuma; Takafumi Nishimori; Daisaku Nogami; Yumiko Oasa; Tatsunori Oda; Tomohito Ohshima; Yoshihiko Saito; Shuichiro Sakata; Shigeyuki Sako; Yuki Sarugaku; Satoko Sawada-Satoh; Genta Seino; Kazuo Sorai; Takao Soyano; Francesco Taddia; Jun Takahashi; Yuhei Takagi; Katsutoshi Takaki; Koji Takata; Ken’ichi Tarusawa; Makoto Uemura; Takahiro Ui; Riku Urago; Kazutoshi Ushioda; Jun-Ichi Watanabe; Makoto Watanabe; Satoshi Yamash*ta; Kenshi Yanagisawa; Yoshinori Yonekura and Michitoshi Yoshida, We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSS J110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to ∼5 μm in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of α ν ∼ -1.4, where fνναν, synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seems most plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low ν peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations., Oxford University Press
Publ. Astron. Soc. Japan, Oct. 2017, [Reviewed]

The shortest periodic and flaring flux variability of a methanol maser emission at 6.7 GHz in G 014.23-00.50
Koichiro Sugiyama; Katsura Nagase; Yoshinori Yonekura; Munetake Momose; Yasutaka Yasui; Yu Saito; Kazuhito Motogi; Mareki Honma; Kazuya Hachisuka; Naoko Matsumoto; Mizuho Uchiyama; and Kenta Fujisawa, We detected flaring flux variability that regularly occurred with a period of 23.9 d on a 6.7 GHz methanol maser emission at V-lsr = 25.30 km s(-1) in G 014.23-00.50 through highly frequent monitoring using the Hitachi 32m radio telescope. Analyzing data from 2013 January 5 to 2016 January 21, the periodic variability has persisted in at least 47 cycles, corresponding to similar to 1100 d. The period of 23.9 d is the shortest one observed in masers around high-mass young stellar objects so far. The flaring component normally falls below the detection limit (3 sigma) of similar to 0.9 Jy. In the flaring periods, the component rises above the detection limit with a ratio of the peak flux density more than 180 in comparison with the quiescent phase, showing intermittent periodic variability. The timescale of the flux rise was typically two days or shorter, and both symmetric and asymmetric profiles of flux variability were observed through intraday monitoring. These characteristics might be explained by a change in the flux of seed photons in a colliding-wind binary (CWB) system, or a variation of the dust temperature by the extra heating source of a shock formed by a CWB system within a gap region in a circumbinary disk, in which the orbital semi-major axes of the binary are 0.26-0.34 au., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Aug. 2017, [Reviewed]

HCN hyperfine ratio analysis of massive molecular clumps
W. J. Schap; P. J. Barnes; A. Ordñez; A. Ginsburg; Y. Yonekura; Y. f*ckui, We report a new analysis protocol for HCN hyperfine data, based on the PYSPECKIT package, and results of using this new protocol to analyse a sample area of seven massive molecular clumps from the Census of High- and Medium-mass Protostars (CHaMP) survey, in order to derive maps of column density for this species. There is a strong correlation between the HCN integrated intensity, IHCN, and previously reported IHCO+ in the clumps, but IN2H+ is not well correlated with either of these other two 'dense gas tracers'. The four fitted parameters from PYSPECKIT in this region fall in the range of VLSR = 8-10 km s-1, σV = 1.2-2.2 km s-1, Tex = 4-15 K, and τ = 0.2-2.5. These parameters allow us to derive a column density map of these clouds, without limiting assumptions about the excitation or opacity. A more traditional (linear) method of converting IHCN to total mass column gives much lower clump masses than our results based on the hyperfine analysis. This is primarily due to areas in the sample region of low I, lowTex, and high τ. We conclude that there may be more dense gas in these massive clumps not engaged in massive star formation than previously recognized. If this result holds for other clouds in the CHaMP sample, it would have dramatic consequences for the calibration of the Kennicutt-Schmidt star formation laws, including a large increase in the gas depletion time-scale in such regions., Oxford University Press
Monthly Notices of the Royal Astronomical Society, 2017, [Reviewed]

Wide-Band Spectra of Giant Radio Pulses from the Crab Pulsar
Ryo Mikami; Katsuaki Asano; Shuta J. Tanaka; Shota Kisaka; Mamoru Sekido; Kazuhiro Takefuji; Hiroshi Takeuchi; Hiroaki Misawa; Fuminori Tsuchiya; Hajime Kita; Yoshinori Yonekura; and Toshio Terasawa, © 2016. The American Astronomical Society. All rights reserved.. We present the results of the simultaneous observation of giant radio pulses (GRPs) from the Crab pulsar at 0.3, 1.6, 2.2, 6.7, and 8.4 GHz with four telescopes in Japan. We obtain 3194 and 272 GRPs occurring at the main pulse and the interpulse phases, respectively. A few GRPs detected at both 0.3 and 8.4 GHz are the most wide-band samples ever reported. In the frequency range from 0.3 to 2.2 GHz, we find that about 70% or more of the GRP spectra are consistent with single power laws and their spectral indices are distributed from -4 to -1. We also find that a significant number of GRPs have such a hard spectral index (approximately -1) that the fluence at 0.3 GHz is below the detection limit ("dim-hard" GRPs). Stacking light curves of such dim-hard GRPs at 0.3 GHz, we detect consistent enhancement compared to the off-GRP light curve. Our samples show apparent correlations between the fluences and the spectral hardness, which indicates that more energetic GRPs tend to show softer spectra. Our comprehensive studies on the GRP spectra are useful materials to verify the GRP model of fast radio bursts in future observations.
Astrophys. J., Dec. 2016, [Reviewed]

The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy
Yoshinori Yonekura; Yu Saito; Koichiro Sugiyama; Kang Lou Soon; Munetake Momose; Masayoshi Yokosawa; Hideo Ogawa; Kimihiro Kimura; Yasuhiro Abe; Atsushi Nishimura; Yutaka Hasegawa; Kenta Fujisawa; Tomoaki Ohyama; Yusuke Kono; Yusuke Miyamoto; Satoko Sawada-Satoh; Hideyuki Kobayashi; Noriyuki Kawaguchi; Mareki Honma; Katsunori M. Shibata; Katsuhisa Sato; Yuji Ueno; Takaaki Jike; Yoshiaki Tamura; Tomoya Hirota; Atsushi Miyazaki; Kotaro Niinuma; Kazuo Sorai; Hiroshi Takaba; Kazuya Hachisuka; Tetsuro Kondo; Mamoru Sekido; Yasuhiro Murata; Naomasa Nakai; and Toshihiro Omodaka, Lead, The Hitachi and Takahagi 32 m radio telescopes (former satellite communication antennas) were so upgraded as to work at 6, 8, and 22 GHz. We developed the receiver systems, IF systems, back-end systems (including samplers and recorders), and reference systems. We measured the performance of the antennas. The system temperature including the atmosphere toward the zenith, T*(sys), is measured to be similar to 30-40 K for 6 GHz and similar to 25-35 K for 8 GHz. T*(sys) for 22 GHz is measured to be similar to 40-100 K in winter and similar to 150-500K in summer seasons, respectively. The aperture efficiency is 55%-75% for Hitachi at 6 GHz and 8 GHz, and 55%-65% for Takahagi at 8 GHz. The beam sizes at 6 GHz and 8 GHz are similar to 4.'6 and similar to 3.'8, respectively. The side-lobe level is less than 3%-4% at 6 and 8 GHz. Pointing accuracy was measured to be better than similar to 0.'3 for Hitachi and similar to 0.'6 for Takahagi. We succeeded in VLBI observations in 2010 August, indicating good performance of the antenna. We started single-dish monitoring observations of 6.7 GHz methanol maser sources in 2012 December, and found several new sources showing short-term periodic variation of the flux density., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Oct. 2016, [Reviewed]

Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. II. Internal proper motion measurement in G 006.79−00.25
Koichiro Sugiyama; Kenta Fujisawa; Kazuya Hachisuka; Yoshinori Yonekura; Kazuhito Motogi; Satoko Sawada-Satoh; Naoko Matsumoto; Daiki Hirano; Kyonosuke Hayashi; Hideyuki Kobayashi; Noriyuki Kawaguchi; Katsunori M. Shibata; Mareki Honma; Tomoya Hirota; Yasuhiro Murata; Akihiro Doi; Hideo Ogawa; Kimihiro Kimura; Kotaro Niinuma; Xi Chen; Bo Xia; Bin Li; Kazuo Sorai; Munetake Momose; Yu Saito; Hiroshi Takaba; Toshihiro Omodaka; Kee-Tae Kim; and Zhiqiang Shen
Publ. Astron. Soc. Japan, Oct. 2016, [Reviewed]

Accelerating a water maser face-on jet from a high mass young stellar object
Kazuhito Motogi; Kazuo Sorai; Mareki Honma; Tomoya Hirota; Kazuya Hachisuka; Kotaro Niinuma; Koichiro Sugiyama; Yoshinori Yonekura; Kenta Fujisawa, We report on a long-term single-dish and VLBI monitoring for intermittent flare activities of a Dominant Blue-Shifted H$_{2}$O Maser (DBSM) associated with a southern high mass young stellar object, G353.273+0.641. Bi-weekly single-dish monitoring using Hokkaido University Tomakomai 11-m radio telescope has shown that a systematic acceleration continues over four years beyond a lifetime of individual maser features. This fact suggests that the H$_{2}$O maser traces a region where molecular gas is steadily accelerated. There were five maser flares during five-years monitoring, and maser distributions in four of them were densely monitored by the VLBI Exploration of Radio Astrometry (VERA). The overall distribution of the maser features suggests the presence of a bipolar jet, with the 3D kinematics indicating that it is almost face-on (inclination angle of $\sim$ 8$^{\fdg}$--17$^{\fdg}$ from the line-of-sight). Most of maser features were recurrently excited within a region of 100$\times$100 AU$^{2}$ around the radio continuum peak, while their spatial distributions significantly varied between each flare. This confirms that episodic propagations of outflow shocks recurrently invoke intermittent flare activities. We also measured annual parallax, deriving the source distance of 1.70 $^{+0.19}_{-0.16}$ kpc that is consistent with the commonly-used photometric distance.
Publ. Astron. Soc. Japan, Oct. 2016, [Reviewed]

Z45: A New 45-GHz band dual-polarization HEMT receiver for the NRO 45-m radio telescope
Fumitaka Nakamura; Hideo Ogawa; Yoshinori Yonekura; Kimihiko Kimura; Nozomi Okada; Minato Kozu; Yutaka Hasegawa; Kazuki Tokuda; Tetsu Ochiai; Izumi Mizuno; Kazuhito Dobashi; Tomomi Shimoikura; Seiji Kameno; Kotomi Taniguchi; Hiroko Shinnaga; Shuro Takano; Ryohei Kawabe; Taku Nakajima; Daisuke Iono; Nario Kuno; Toshikazu Onishi; Munetake Momose; and Satoshi Yamamoto
Publ. Astron. Soc. Japan, Dec. 2015, [Reviewed]

No Microwave Flare of Sagittarius A* around the G2 Periastron Passing　　　　　　　　　　　　　　　
Masato Tsuboi; Yoshiharu Asaki; Osamu Kameya; Yoshinori Yonekura; Yusuke Miyamoto; Hiroyuki Kaneko; Masumichi Seta; Naomasa Nakai; Hiroshi Takaba; Ken-ichi Wakamatsu; Makoto Miyoshi; Yoshihiro f*ckuzaki; Kenta Uehara; and Mamoru Sekido
Astrophys. J. Letter, Jan. 2015, [Reviewed]

Cluster Formation Triggered by Filament Collisions in Serpens South
Fumitka Nakamura; Tomohiro Tanaka; Yuya Awazu; Yosh*to Shimajiri; Koji Sugitani; Ryohei Kawabe; Hiroyuki Nish*tani; Kazuhito Dobashi; Tomomi Shimoikura; Yoshinori Yonekura; Izumi Mizuno; Kimihiko Kimura; Kazuki Tokuda; Minato Kozu; Nozomi Okada; Yutaka Hasegawa; Hideo Ogawa; Seiji Kameno; Hiroko Shinnaga; Munetake Momose; Taku Nakajima; Toshikazu Onishi; Hiroyuki Maezawa; Tomoya Hirota; Shuro Takano; Daisuke Iono; Nario Kuno; Satoshi Yamamoto, Serpens South is a nearby infrared dark cloud (IRDC), consisting of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS (J(N) = 4(3) - 3(2)) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament. We emphasize that Serpens South IRDC is the first cluster-forming region with extremely-strong CCS emission. We identify 6 ridges from the Herschel column density map. These ridges appear to converge toward the protocluster clump, suggesting that the collisions of these ridges may have triggered cluster formation. The collisions presumably happened within the last few x10(5) yr because the chemical evolution calculation indicates that CCS is abundant only in the first few x10(5) yr., ASTRONOMICAL SOC PACIFIC
REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR, 2015, [Reviewed]

VERA and ALMA observations of the H2O supermaser burst in Orion KL
Tomoya Hirota; Masato Tsuboi; Yasutaka Kurono; Kenta Fujisawa; Mareki Honma; Mi Kyoung Kim; Hiroshi Imai; And Yoshinori Yonekura, The 22 GHz H2O maser in Orion KL has shown extraordinary burst events in 1979-1985 and 1998-1999, sometimes called supermaser. We have conducted monitoring observations of the supermaser in Orion KL using VERA (VLBI Exploration of Radio Astrometry) in the current third burst since 2011 March. Three flux maxima are detected in 2011 and 2012 with rising and falling timescales of 2-7 months. Time variations of the supermaser seem symmetric for all of the active phases. The maximum total flux density of 135000 Jy is observed in 2012 June while it is still one order of magnitude lower than those in previous bursts. The supermaser consists of two spatially different components at different velocities. They are elongated along a northwest-southeast direction perpendicular to the low-velocity outflow driven by Source I. Proper motions of the supermaser features with respect to Source I are measured toward west and southwest directions, almost parallel to the low-velocity outflow. The flux density and linewidth show an anti-correlation as expected for an unsaturated maser emission. The supermaser is located close to the methylformate (HCOOCH3) line and continuum emission peaks in the Orion Compact Ridge detected by ALMA (Atacama Large Millimeter/Submillimeter Array). The broader velocity range of the weak HCOOCH3 emission at the supermaser position would be evidence of a shock front. On the other hand, the 321 GHz H2O line is not detected at the position of the supermaser. It can be explained qualitatively by one of the theoretical H2O excitation models without extraordinary conditions. Our results support a scenario that the supermaser is excited in the dense gas interacting with the low-velocity outflow in the Compact Ridge. The extremely high flux density and its symmetric time variation for rising and falling phases could be explained by a beaming effect during the amplification process rather than changes in physical conditions., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Dec. 2014, [Reviewed]

Observations of the bursting activity of the 6.7 GHz methanol maser in G33.641−0.228
Kenta Fujisawa; Nozomu Aoki; Yosh*to Nagadomi; Saki Kimura; Tadashi Shimomura; Genta Takase; Koichiro Sugiyama; Kazuhito Motogi; Kotaro Niinuma; Tomoya Hirota; And Yoshinori Yonekura, We have observed bursting variability of the 6.7 GHz methanol maser of G33.641-0.228. Five bursts were detected in the observation period of 294 days from 2009 to 2012. The typical burst is a large flux density rise in about one day followed by a slow fall. A non-typical burst observed in 2010 showed a large and rapid flux density enhancement from the stable state, but the rise and fall of the flux density were temporally symmetric and a fast fluctuation continued for 12 days. On average, the bursts occurred once every 59 days, although bursting was not periodic. Since the average power required for causing a burst of order of 10(21) Js(-1) is far smaller than the luminosity of G33.641-0.228, a very small fraction of the source's power would be sufficient to cause the burst occasionally. The burst can be explained as a solar-flare-like event in which the energy is accumulated in the magnetic field of the circ*mstellar disk, and is released for a short time. However, the mechanism of the energy release and the dust heating process are still unknown., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Dec. 2014, [Reviewed]

Periodic Flare of the 6.7 GHz Methanol Maser in IRAS22198+6336
Kenta Fujisawa; Genta Takase; Saki Kimura; Nozomu Aoki; Yosh*to Nagadomi; Tadashi Shimomura; Koichiro Sugiyama; Kazuhito Motogi; Kotaro Niinuma; Tomoya Hirota; and Yoshinori Yonekura, We have detected periodic flares of the 6.7-GHz methanol maser from an intermediate-mass star-forming region IRAS 22198+6336. The maser was monitored daily in 2011, 2012, and 2013. Six flares were observed with a period of 34.6 d. The variation pattern is intermittent, and the flux ratio of the flaring and the quiescent states exceeds 30. Such intermittent variation with the short period uniquely characterizes the variation of the IRAS 22198+6336 maser. At least five spectral components were identified. The spectral components varied almost synchronously, but their peak times differed by 1.8 d. These characteristics can be explained by the colliding-wind binary model., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Aug. 2014, [Reviewed]

Cluster Formation Triggered by Filament Collisions in Serpens South
Fumitaka Nakamura; Koji Sugitani; Tomohiro Tanaka; Hiroyuki Nish*tani; Kazuhito Dobashi; Tomomi Shimoikura; Yosh*to Shimajiri; Ryohei Kawabe; Yoshinori Yonekura; Izumi Mizuno; Kimihiro Kimura; Kazuki Tokuda; Minato Kozu; Nozomi Okada; Yutaka Hasegawa; Hideo Ogawa; Tac Nakajima; Seiji Kameno; Hiroko Shinnaga; Munetake Momose; Hiroyuki Maezawa; Toshikazu Onishi; Tomoya HIROTA; Shuro Takano; Daisuke Iono; Nario Kuno; and Satoshi Yamamoto, The Serpens South infrared dark cloud consists of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS (J(N) = 4(3)-3(2)), HC3N (J = 5-4), N2H+ (J = 1-0), and SiO (J = 2-1, v = 0) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament in the protocluster clump. We emphasize that Serpens South is the first cluster-forming region where extremely strong CCS emission is detected. The CCS-to-N2H+ abundance ratio is estimated to be about 0.5 toward the protocluster clump, whereas it is about 3 in the other parts of the main filament. We identify six dense ridges with different V-LSR. These ridges appear to converge toward the protocluster clump, suggesting that the collisions of these ridges may have triggered cluster formation. The collisions presumably happened within a few x 10(5) yr because CCS is abundant only for a short time. The short lifetime agrees with the fact that the number fraction of Class I objects, whose typical lifetime is 0.4 x 10(5) yr, is extremely high, about 70% in the protocluster clump. In the northern part, two ridges appear to have partially collided, forming a V-shape clump. In addition, we detected strong bipolar SiO emission that is due to the molecular outflow blowing out of the protostellar clump, as well as extended weak SiO emission that may originate from the filament collisions., IOP PUBLISHING LTD
Astrophys. J. Letter, Aug. 2014, [Reviewed]

Daily monitor of Sagittarius A* at 22 GHz with the Japanese VLBI Network
M. Tsuboi; Y. Asaki; Y. Yonekura; Y. Miyamoto; H. Kaneko; M. Seta; N. Nakai; O. Kameya; M. Miyoshi; H. Takaba; K. Wakamatsu; Y. f*ckuzaki; T. Morimitsu; K. Uehara; M. Sekido; T. Oka; S. Takekawa; T. Omodaka; T. Handa; A. Takumi, We have been monitoring the flux density of Sagittarius A* (Sgr A*) at 22 GHz since DOY=42 (11 Feb. 2013) with a sub-array of the Japanese VLBI Network in order to search the increase of 22-GHz emission from Sgr A* induced by the interaction of the G2 cloud with the accretion disk. The flux densities observed until DOY=322 (18 Nov. 2013) are consistent with the previously observed values before the approaching of the cloud. We have detected no large flare during this period. Copyright © International Astronomical Union 2014., Proceedings of the International Astronomical Union
Proceedings of the International Astronomical Union, May 2014

Observations of 6.7 GHz Methanol Masers with EAVN I: VLBI Images of the first Epoch of Observations
K. Fujisawa; K. Sugiyama; K. Motogi; K. Hachisuka; Y. Yonekura; S. Sawada-Satoh; N. Matsumoto; K. Sorai; M. Momose; Y. Saito; H. Takaba; H. Ogawa; K. Kimura; K. Niinuma; D. Hirano; T. Omodaka; H. Kobayashi; N. Kawaguchi; K. M. Shibata; M. Honma; T. Hirota; Y. Murata; A. Doi; N. Mochizuki; Z. Shen; X. Chen; B. Xia; B. Li; K.-T. Kim, Very-long-baseline interferometry (VLBI) monitoring of the 6.7 GHz methanol maser allows us to measure the internal proper motion of maser spots and therefore study the gas motion around high-mass young stellar objects. To this end, we have begun monitoring observations with the East-Asian VLBI Network. In this paper we present the results of the first epoch observation for 36 sources, including 35 VLBI images of the methanol maser. Since two independent sources were found in three images, images of 38 sources were obtained. In 34 sources, 10 or more spots were detected. The observed spatial scale of the maser distribution was from 9 to 4900 astronomical units, and the following morphological categories were observed: elliptical, arched, linear, paired, and complex. The position of the maser spot was determined with an accuracy of approximately 0.1 mas, which is sufficiently high to measure the internal proper motion from two years of monitoring observations. The VLBI observation, however, detected only approximately 20% of all maser emissions, suggesting that the remaining 80% of the total flux was spread into an undetectable extended distribution. Therefore, in addition to high-resolution observations, it is important to observe the whole structure of the maser emission including extended low-brightness structures, in order to reveal the associated site of the maser and gas motion., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Apr. 2014, [Reviewed]

THE JET AND ARC MOLECULAR CLOUDS TOWARD WESTERLUND 2, RCW 49, AND HESS J1023-575; (CO)-C-12 AND (CO)-C-13 (J=2-1 and J=1-0) OBSERVATIONS WITH NANTEN2 AND MOPRA TELESCOPE
N. Furukawa; A. Ohama; T. f*ckuda; K. Torii; T. Hayakawa; H. Sano; T. Okuda; H. Yamamoto; N. Moribe; A. Mizuno; H. Maezawa; T. Onishi; A. Kawamura; N. Mizuno; J. R. Dawson; T. M. Dame; Y. Yonekura; F. Aharonian; E. de Ona Wilhelmi; G. P. Rowell; R. Matsumoto; Y. Asahina; Y. f*ckui, We have made new CO observations of two molecular clouds, which we call "jet" and "arc" clouds, toward the stellar cluster Westerlund 2 and the TeV gamma-ray source HESS J1023-575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023-575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be similar to Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV gamma-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV gamma-rays, although none of the known microquasars have a Myr age or steady TeV gamma-rays. Alternatively, an anisotropic supernova explosion which occurred similar to Myr ago may be able to form the jet and arc clouds, whereas the TeV gamma-ray emission requires a microquasar formed after the explosion., IOP PUBLISHING LTD
ASTROPHYSICAL JOURNAL, Feb. 2014, [Reviewed]

Short-Term Radio Variability and Parsec-Scale Structure in a Gamma-Ray Narrow-Line Seyfert 1 Galaxy 1H 0323+342
K. Wajima; K. Fujisawa; M. Hayashida; N. Isobe; T. Ishida; Y. Yonekura, We made simultaneous single-dish and very long baseline interferometer (VLBI) observations of a narrow-line Seyfert 1 galaxy 1H 323+342, showing gamma-ray activity revealed by Fermi/Large Area Telescope observations. We found significant variation of the total flux density at 8 GHz on the timescale of one month by the single-dish monitoring. The total flux density varied by 5.5% in 32 days, which is comparable to the gamma-ray variability timescale, corresponding to the variability brightness temperature of 7.0 x 10(11) K. The source consists of central and southeastern components on the parsec (pc) scale. Only the flux of the central component decreased in the same way as the total flux density, indicating that the short-term radio variability, and probably the gamma-ray-emitting region, is associated with this component. From the VLBI observations, we obtained brightness temperatures of greater than (5.2 +/- 0.3) x 10(10) K and derived an equipartition Doppler factor of greater than 1.7, a variability Doppler factor of 2.2, and an 8 GHz radio power of 10(24.6) W Hz(-1). Combining them, we conclude that acceleration of radio jets and creation of high-energy particles are ongoing in the central engine and that the apparent very radio-loud feature of the source is due to the Doppler boosting effect, resulting in the intrinsic radio loudness being an order of magnitude smaller than the observed values. We also conclude that the pc-scale jet represents recurrent activity from the spectral fitting and the estimated kinematic age of pc- and kpc-scale extended components with different position angles., IOP PUBLISHING LTD
Astrophys. J., Feb. 2014, [Reviewed]

The Jet and Arc Molecular Clouds Toward Westerlund 2, RCW 49, and HESS J1023-575; 12CO and 13CO (J=2-1 and J=1-0) Observations with NANTEN2 and Mopra
N. Furukawa; A. Ohama; T. f*ckuda; K. Torii; T. Hayakawa; H. Sano; T. Okuda; H. Yamamoto; N. Moribe; A. Mizuno; H. Maezawa; T. Onishi; A. Kawamura; N. Mizuno; J. R. Dawson; T. M. Dame; Y. Yonekura; F. Aharonian; E. de Oña Wilhelmi; G. P. Rowell; R. Matsumoto; Y. Asahina; and Y. f*ckui, We have made new CO observations of two molecular clouds, which we call jet and arc clouds, toward the stellar cluster Westerlund 2 and the TeV γ-ray source HESS J1023-575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023-575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ-rays, although none of the known microquasars have a Myr age or steady TeV γ-rays. Alternatively, an anisotropic supernova explosion which occurred Myr ago may be able to form the jet and arc clouds, whereas the TeV γ-ray emission requires a microquasar formed after the explosion. © 2014. The American Astronomical Society. All rights reserved., Institute of Physics Publishing
Astrophys. J., Feb. 2014, [Reviewed]

A 1.85-m mm-submm Telescope for Large-Scale Molecular Gas Surveys in (CO)-C-12, (CO)-C-13, and (CO)-O-18 (J=2-1)
Onishi Toshikazu; Nishimura Atsushi; Ota Yuya; Hashizume Akio; Kojima Yoshiharu; Minami Akihito; Tokuda Kazuki; Touga Shiori; Abe Yasuhiro; Kaiden Masahiro; Kimura Kimihiro; Muraoka Kazuyuki; Maezawa Hiroyuki; Ogawa Hideo; Dobashi Kazuhito; Shimoikura Tomomi; Yonekura Yoshinori; Asayama Shin'ichiro; Handa Toshihiro; Nakajima Taku; Noguchi Takashi; Kuno Nario
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, Aug. 2013, [Reviewed]

A 1.85 m Mm-Submm Telescope for Large-Scale Molecular Gas Survey in 12CO, 13CO and C18O (J = 2 − 1)
T. Onishi; A. Nishimura; Y. Ota; A. Hashizume; Y. Kojima; A. Minami; K. Tokuda; S. Touga; Y. Abe; M. Kaiden; K. Kimura; K. Muraoka; H. Maezawa; H. Ogawa; K. Dobashi; T. Shimoikura; Y. Yonekura; S. Asayama; T. Handa; T. Nakajima; T. Noguchi; And N. Kuno, We have developed a new mm-submm telescope with a diameter of 1.85-m installed at the Nobeyama Radio Observatory. The scientific goal is to precisely reveal the physical properties of molecular clouds in the Milky Way Galaxy by obtaining a large-scale distribution of molecular gas, which can also be compared with large-scale observations at various wavelengths. The target frequency is ̃230 GHz
simultaneous observations at the molecular rotational lines of J = 2-1 of three carbon monoxide isotopes (12CO, 13CO, C18O) are achieved with a beam size (HPBW) of 2:07. In order to accomplish the simultaneous observations, we have developed waveguide-type sidebandseparating SIS mixers to obtain spectra separately in the upper and lower side bands. A Fourier digital spectrometer with a 1 GHz bandwidth having 16384 channels is installed, and the bandwidth of the spectrometer is divided into three parts, corresponding to each of the three spectra
the IF system has been designed so as to inject these three lines into the spectrometer. A flexible observation system was created mainly in Python on Linux PCs, enabling effective OTF (On-The-Fly) scans for large-area mapping. The telescope is enclosed in a radome with a membrane covered to prevent any harmful effects of sunlight, strong wind, and precipitation in order to minimize errors in the telescope pointing, and to stabilize the receiver and the IF devices. From 2011 November, we started science operation, resulting in a large-scale survey of the Orion A/B clouds, Cygnus OB7, Galactic Plane, Taurus, and so on. We also updated the receiver system for dual-polarization observations. © 2013. Astronomical Society of Japan., Oxford University Press
Publ. Astron. Soc. Japan, Aug. 2013, [Reviewed]

Dense Optical and Near-infrared Monitoring of CTA 102 during High State in 2012 with OISTER: Detection of Intra-night "Orphan Polarized Flux Flare"
R. Itoh; Y. f*ckazawa; Y. T. Tanaka; Y. Abe; H. Akitaya; A. Arai; M. Hayashi; T. Hori; M. Isogai; H. Izumiura; K. S. Kawabata; N. Kawai; D. Kuroda; R. Miyanosh*ta; Y. Moritani; T. Morokuma; T. Nagayama; J. Nakamoto; C. Nakata; Y. Oasa; T. Ohshima; T. Ohsugi; S.-i. Okumura; Y. Saito; Y. Saito; M. Sasada; K. Sekiguchi; Y. Takagi; J. Takahashi; Y. Takahashi; K. Takaki; M. Uemura; I. Ueno; S. Urakawa; M. Watanabe; M. Yamanaka; Y. Yonekura; M. Yoshida, CTA 102, classified as a flat spectrum radio quasar at z = 1.037, produced an exceptionally bright optical flare in 2012 September. Following the Fermi Large Area Telescope detection of enhanced gamma-ray activity, we closely monitored this source in the optical and near-infrared bands for the 10 subsequent nights using 12 telescopes in Japan and South Africa. On MJD 56197 (2012 September 27, four to five days after the peak of bright gamma-ray flare), polarized flux showed a transient increase, while total flux and polarization angle (PA) remained almost constant during the "orphan polarized-flux flare." We also detected an intra-night and prominent flare on MJD 56202. The total and polarized fluxes showed quite similar temporal variations, but the PA again remained constant during the flare. Interestingly, the PAs during the two flares were significantly different from the jet direction. The emergence of a new emission component with a high polarization degree (PD) up to 40% would be responsible for the observed two flares, and such a high PD indicates the presence of a highly ordered magnetic field at the emission site. We argue that the well-ordered magnetic field and even the observed directions of the PA, which is grossly perpendicular to the jet, are reasonably accounted for by transverse shock(s) propagating down the jet., IOP PUBLISHING LTD
Astrophys. J. Letter, May 2013, [Reviewed]

The VLBI Imaging Survey of the 6.7 GHz Methanol Masers using the JVN/EAVN
K. Sugiyama; K. Fujisawa; K. Hachisuka; Y. Yonekura; K. Motogi; M. Honma; T. Hirota; S. Sawada-Satoh; K. Niinuma; Y. Murata; A. Doi; H. Ogawa; Z. -Q. Shen, We present a result of the VLBI (very-long-baseline-interferometer) imaging survey for the 6.7 GHz methanol masers by using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). We conducted VLBI observations for 36 methanol maser sources, and the spatial distribution of 35 sources were obtained, in which 33 sources provide new VLBI images. The spatial morphology was classified into five categories on the basis of the criteria used in the European VLBI Network observations (EVN: Bartkiewicz et al. 2009)., ASTRONOMICAL SOC PACIFIC
NEW TRENDS IN RADIO ASTRONOMY IN THE ALMA ERA: THE 30TH ANNIVERSARY OF NOBEYAMA RADIO OBSERVATORY, 2013

High-Resolution Observations of Centimeter/(Sub)Millimeter H2O Masers in Orion KL with VERA and ALMA
T. Hirota; M. Tsuboi; K. Fujisawa; M. Honma; N. Kawaguchi; M. K. Kim; H. Kobayashi; Y. Kurono; H. Imai; T. Omodaka; K. M. Shibata; T. Shimoikura; Y. Yonekura, We present the results of astrometry with VERA of the 22 GHz H2O maser burst in Orion KL started since 2011 February. According to the absolute positions and proper motions of the bursting H2O maser features, it is most likely that the outflow from the radio Source I or another young stellar object in the Compact Ridge is a possible origin of the burst. In addition, we report the first detection of the 232 GHz vibrationally excited H2O maser in star-forming regions by using the ALMA Science Verification data of Orion KL. The 232 GHz H2O maser is detected toward the Source I and its spectral profile shows a double-peaked structure analogous to the 22 GHz H2O and 43 GHz SiO masers. Thus, the 232 GHz H2O maser would be excited in the dense and hot gas around the Source I as in the case of other maser lines., ASTRONOMICAL SOC PACIFIC
NEW TRENDS IN RADIO ASTRONOMY IN THE ALMA ERA: THE 30TH ANNIVERSARY OF NOBEYAMA RADIO OBSERVATORY, 2013, [Reviewed]

The VLBI mapping survey of the 6.7 GHz methanol masers with the JVN/EAVN
K. Fujisawa; K. Hachisuka; K. Sugiyama; A. Doi; M. Honma; Y. Yonekura; T. Hirota; S. Sawada-Satoh; Y. Murata; K. Motogi; H. Ogawa; X. Chen; K. T. Kim; Z. Q. Shen, We present VLBI maps of the 6.7 GHz methanol maser emission in 32 sources obtained using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). All of the observed sources provide new VLBI maps, and the spatial morphologies have been classified into five categories similar to the results obtained from European VLBI Network observations (Bartkiewicz et al. 2009). The 32 methanol sources are being monitored to measure the relative proper motions of the methanol maser spots. Copyright © International Astronomical Union 2012.
Proceedings of the International Astronomical Union, Jul. 2012

VERA observations of the H2O maser burst in orion KL
Tomoya Hirota; Masato Tsuboi; Kenta Fujisawa; Mareki Honma; Noriyuki Kawaguchi; Mi Kyoung Kim; Hideyuki Kobayashi; Hiroshi Imai; Toshihiro Omodaka; Katsunori M. Shibata; Tomomi Shimoikura; Yoshinori Yonekura, In 2011 February, a burst of the 22 GHz H2O maser in Orion KL was reported. In order to identify the bursting maser features, we have been carrying out observations of the 22 GHz H2O maser in Orion KL with VERA, a Japanese VLBI network dedicated for astrometry. The bursting maser turns out to consist of two spatially different features at 7.58 and 6.95 km s-1. We determine their absolute positions and find that they are coincident with the shocked molecular gas called the Orion Compact Ridge. We tentatively detect the absolute proper motions of the bursting features toward the southwest direction, perpendicular to the elongation of the maser features. It is most likely that the outflow from the radio source I or another young stellar object interacting with Compact Ridge is a possible origin of the H2O maser burst. We will also carry out observations with ALMA in the cycle 0 period to monitor the submillimeter H2O maser lines in the Orion Compact Ridge region. These follow-up observations will provide novel information on the physical and chemical properties of the mastering region. Copyright © International Astronomical Union 2012.
Proceedings of the International Astronomical Union, Jul. 2012, [Reviewed]

Bursting Activity in a High-Mass Star-Forming Region G33.64-0.21 Observed with the 6.7 GHz Methanol Maser
Kenta Fujisawa; Koichiro Sugiyama; Nozomu Aoki; Tomoya Hirota; Nanako Mochizuki; Akihiro Doi; Mareki Honma; Hideyuki Kobayashi; Noriyuki Kawaguchi; Hideo Ogawa; Toshihiro Omodaka; Yoshinori Yonekura, We report on the detection of bursts of 6.7 GHz methanol maser emission in a high-mass star-forming region, G33.64-0.21. One of the spectral components of the maser in this source changed its flux density by 7 times that of the previous day, and it decayed with a timescale of 5 days. The burst occurred repeatedly in the spectral component, and no other components showed such variability. A VLBI observation with the Japanese VLBI Network (JVN) showed that the burst location was at the southwest edge of a spatial distribution, and the bursting phenomenon occurred in a region much smaller than 70 AU. We suggest an impulsive energy release, like a stellar flare, as a possible mechanism for the burst. These results imply that 6.7 GHz methanol masers could be a useful new probe for studying bursting activity in the process of the star formation of high-mass YSOs with a high-resolution of AU scale., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Feb. 2012, [Reviewed]

Identification of Bursting Water Maser Features in Orion KL　　　　　　　　　　　　　　　
Tomoya Hirota; Masato Tsuboi; Kenta Fujisawa; Mareki Honma; Noriyuki Kawaguchi; Mi Kyoung Kim; Hideyuki Kobayashi; Hiroshi Imai; Toshihiro Omodaka; Katsunori; M. Shibata; Tomomi Shimoikura; Yoshinori Yonekura
Astrophys. J. Letter, Oct. 2011, [Reviewed]

The Galactic Census of High- and Medium-Mass Protostars. I. Catalogs and First Results from Mopra HCO+ Maps
Peter J. Barnes; Yoshinori Yonekura; Yasuo f*ckui; Andrew T. Miller; Martin Mühlegger; Lawrence C. Agars; Yosuke Miyamoto; Naoko Furukawa; George Papadopoulos; Scott L. Jones; Audra K. Hernandez; Stefan N. O'Dougherty and Jonathan C. Tan, The Census of High- and Medium-mass Protostars (CHaMP) is the first large-scale, unbiased, uniform mapping survey at sub-parsec-scale resolution of 90 GHz line emission from massive molecular clumps in the Milky Way. We present the first Mopra (ATNF) maps of the CHaMP survey region (300 degrees > l > 280 degrees) in the HCO+ J = 1 -> 0 line, which is usually thought to trace gas at densities up to 10(11) m(-3). In this paper, we introduce the survey and its strategy, describe the observational and data reduction procedures, and give a complete catalog of moment maps of the HCO+ J = 1 -> 0 emission from the ensemble of 303 massive molecular clumps. From these maps we also derive the physical parameters of the clumps, using standard molecular spectral-line analysis techniques. This analysis yields the following range of properties: integrated line intensity 1-30 K km s(-1), peak line brightness 1-7 K, linewidth 1-10 km s(-1), integrated line luminosity 0.5-200 K km s(-1) pc(2), FWHM size 0.2-2.5 pc, mean projected axial ratio 2, optical depth 0.08-2, total surface density 30-3000 M-circle dot pc(-2), number density (0.2-30) x 10(9) m(-3), mass 15-8000 M-circle dot, virial parameter 1-55, and total gas pressure 0.3-700 pPa. We find that the CHaMP clumps do not obey a Larson-type size-linewidth relation. Among the clumps, there exists a large population of subthermally excited, weakly emitting (but easily detectable) dense molecular clumps, confirming the prediction of Narayanan et al. These weakly emitting clumps comprise 95% of all massive clumps by number, and 87% of the molecular mass, in this portion of the Galaxy; their properties are distinct from the brighter massive star-forming regions that are more typically studied. If the clumps evolve by slow contraction, the 95% of fainter clumps may represent a long-lived stage of pressure-confined, gravitationally stable massive clump evolution, while the CHaMP clump population may not engage in vigorous massive star formation until the last 5% of their lifetimes. The brighter sources are smaller, denser, more highly pressurized, and closer to gravitational instability than the less bright sources. Our data suggest that massive clumps approach critical Bonnor-Ebert-like states at constant density, while others' suggest that lower-mass clumps reach such states at constant pressure. Evidence of global gravitational collapse of massive clumps is rare, suggesting that this phase lasts <1% of the clumps' lifetime., IOP PUBLISHING LTD
Astrophys. J. Suppl. Series, Sep. 2011, [Reviewed]

A Pan-Carina YSO Catalog: Intermediate-Mass Young Stellar Objects in the Carina Nebula Identified via Mid-Infrared Excess Emission
Matthew S. Povich 他14名 (第14著者), We present a catalog of 1439 young stellar objects (YSOs) spanning the 1.42 deg(2) field surveyed by the Chandra Carina Complex Project (CCCP), which includes the major ionizing clusters and the most active sites of ongoing star formation within the Great Nebula in Carina. Candidate YSOs were identified via infrared (IR) excess emission from dusty circ*mstellar disks and envelopes, using data from the Spitzer Space Telescope (the Vela-Carina survey) and the Two-Micron All Sky Survey. We model the 1-24 mu m IR spectral energy distributions of the YSOs to constrain physical properties. Our Pan-Carina YSO Catalog (PCYC) is dominated by intermediate-mass (2 M-circle dot < m less than or similar to 10 M-circle dot) objects with disks, including Herbig Ae/Be stars and their less evolved progenitors. The PCYC provides a valuable complementary data set to the CCCP X-ray source catalogs, identifying 1029 YSOs in Carina with no X-ray detection. We also catalog 410 YSOs with X-ray counterparts, including 62 candidate protostars. Candidate protostars with X-ray detections tend to be more evolved than those without. In most cases, X-ray emission apparently originating from intermediate-mass, disk-dominated YSOs is consistent with the presence of low-mass companions, but we also find that X-ray emission correlates with cooler stellar photospheres and higher disk masses. We suggest that intermediate-mass YSOs produce X-rays during their early pre-main-sequence evolution, perhaps driven by magnetic dynamo activity during the convective atmosphere phase, but this emission dies off as the stars approach the main sequence. Extrapolating over the stellar initial mass function scaled to the PCYC population, we predict a total population of > 2 x 10(4) YSOs and a present-day star formation rate (SFR) of >0.008 M-circle dot yr(-1). The global SFR in the Carina Nebula, averaged over the past similar to 5 Myr, has been approximately constant., IOP PUBLISHING LTD
Astrophys. J. Suppl. Series, May 2011, [Reviewed]

Source Contamination in X-ray Studies of Star-Forming Regions: Application to the Chandra Carina Complex Project
Konstantin V.Getman 他8名 (第8著者), We describe detailed simulations of X-ray-emitting populations to evaluate the levels of contamination by both Galactic and extragalactic X-ray sources unrelated to a star-forming region under study. For Galactic contaminations, we consider contribution from main-sequence stars and giants (not including cataclysmic variables and other classes of accretion-driven X-ray binary systems), as they make the dominant contribution at the position of the Carina Nebula. The simulations take into consideration a variety of technical factors involving a Galactic population synthesis model, stellar X-ray luminosity functions, Chandra telescope response, source detection methodology, and possible spatial variations in the X-ray background and absorption through molecular clouds. When applied to the 1.42 deg(2) field of the Chandra Carina Complex Project (CCCP), the simulations predict similar to 5000 contaminating sources (1 source arcmin(-2) of the survey), evenly distributed across the field. The results of the simulations are further employed in a companion CCCP study to assign membership probabilities to individual sources., IOP PUBLISHING LTD
Astrophys. J. Suppl. Series, May 2011, [Reviewed]

Photon Dominated Regions in NGC 3603
M. Röllig; C. Kramer; C. Rajbahak; T. Minamidani; K. Sun; R. Simon; V. Ossenkopf; M. Cubick; M. Hitschfeld; M. Aravena; F. Bensch; F. Bertoldi; L. Bronfman; M. Fujish*ta; Y. f*ckui; U.U. Graf; N. Honingh; S. Ito; H. Jakob; K. Jacobs; U. Klein; B.-C. Koo; J. May; M. Miller; Y. Miyamoto; N. Mizuno; T. Onishi; Y.-S. Park; J. Pineda; D. Rabanus; H. Sasago; R. Schieder; J. Stutzki; H. Yamamoto; Y. Yonekura, Aims. We aim at deriving the excitation conditions of the interstellar gas as well as the local FUV intensities in the molecular cloud surrounding NGC 3603 to get a coherent picture of how the gas is energized by the central stars.
Methods. The NANTEN2-4 m submillimeter antenna is used to map the [CI] 1-0, 2-1 and CO 4-3, 7-6 lines in a 2' x 2' region around the young OB cluster NGC 3603 YC. These data are combined with (CO)-O-18 2-1 data, HIRES-processed IRAS 60 mu m and 100 mu m maps of the FIR continuum, and Spitzer/IRAC maps.
Results. The NANTEN2 observations show the presence of two molecular clumps located south-east and south-west of the cluster and confirm the overall structure already found by previous CS and (CO)-O-18 observations. We find a slight position offset of the peak intensity of CO and [CI], and the atomic carbon appears to be further extended compared to the molecular material. We used the HIRES far-infrared dust data to derive a map of the FUV field heating the dust. We constrain the FUV field to values of chi = 3-6 x 10(3) in units of the Draine field across the clouds. Approximately 0.2 to 0.3% of the total FUV energy is re-emitted in the [CII] 158 mu m cooling line observed by ISO. Applying LTE and escape probability calculations, we derive temperatures (T-MM1 = 43 K, T-MM2 = 47 K), column densities (N-MM1 = 0.9 x 10(22) cm(-2), N-MM2 = 2.5 x 10(22) cm(-2)) and densities (n(MM1) = 3 x 10(3) cm(-3), n(MM2) = 10(3) - 10(4) cm(-3)) for the two observed molecular clumps MM1 and MM2.
Conclusions. The cluster is strongly interacting with the ambient molecular cloud, governing its structure and physical conditions. A stability analysis shows the existence of gravitationally collapsing gas clumps which should lead to star formation. Embedded IR sources have already been observed in the outskirts of the molecular cloud and seem to support our conclusions., EDP SCIENCES S A
Astron. Astrophys., Jan. 2011, [Reviewed]

The AMANOGAWA-2SB Galactic Plane Survey. I: The Data on the Galactic Equator
Takahiro Yoda; Toshihiro Handa; Kotaro Kohno; Taku Nakajima; Masahiro Kaiden; Yoshinori Yonekura; Hideo Ogawa; Jun-ichi Morino; and Kazuhito Dobashi, Using a waveguide-type sideband-separating receiver (2SB receiver) on the Tokyo-NRO 60-cm telescope (renamed the AMANOGAWA telescope), we carried out simultaneous observations in the (CO)-C-12 (J = 2-1) and (CO)-C-13 (J = 2-1) lines over the galactic plane l = 10 degrees-245 degrees along b = 0 degrees with a 3.'75 grid. Using the (CO)-C-12 (J = 1-0) data of Dame et al. (2001, ApJ, 547,792), who used a beam size almost the same as ours, we show (CO)-C-12 (J = 2-1)/(CO)-C-12 (J = 1-0) and (CO)-C-13 (J = 2-1)/(CO)-C-12 (J = 2-1) intensity ratios on the l-v map and the intensity correlations among the (CO)-C-12 (J = 2-1), (CO)-C-13 (J = 2-1), and (CO)-C-12 (J = 1-0) lines. As a result, a linear correlation between (CO)-C-12 (J = 2-1) and (CO)-C-12 (J = 1-0) and a curved correlation between (CO)-C-12 (J = 2-1) and (CO)-C-13 (J = 2-1), as produced by most of the data, have been found. We investigated these correlations with simple radiative transfer equations to ascertain a number of restrictions on the physical quantities of molecular gas on a galactic scale., OXFORD UNIV PRESS
Publ. Astron. Soc. Japan, Oct. 2010, [Reviewed]

The Radio-FIR correlation in the Milky Way
Zhang; J.; Hopkins; A.; Barnes; P.J.; Cagnes; M.; Yonekura; Y.; f*ckui; Y., We investigate the scale on which the correlation arises between the 843 MHz radio and the 60 mm far-infrared (FIR) emission from star forming regions in the Milky way. The correlation, which exists on the smallest scales investigated (down to approximate to 4 pc), becomes noticeably tight on fields of size 300, corresponding to physical scales of approximate to 20-50 pc. The FIR to radio flux ratio on this scale is consistent with the radio emission being dominated by thermal emission. We also investigate the location dependence of q(mean), a parameter measuring the mean FIR to radio flux ratio, of a sample of star forming regions. We show that qmean displays a modest dependence on galactic latitude. If this is interpreted as a dependence on the intensity of star formation activity, the result is consistent with studies of the Large Magellanic Cloud (LMC) and other nearby galaxies that show elevated values for q in regions of enhanced star formation., CSIRO PUBLISHING
Publications of the Astronomical Society of Australia, Sep. 2010, [Reviewed]

Discovery of large-scale gravitational infall in a massive protostellar cluster
Peter J. Barnes; Yoshinori Yonekura; Stuart D. Ryder; Andrew M. Hopkins; Yosuke Miyamoto; Naoko Furukawa; and Yasuo f*ckui, We report Mopra Australia Telescope National Facility (ATNF), Anglo-Australian Telescope and Atacama Submillimeter Telescope Experiment observations of a molecular clump in Carina, BYF73 = G286.21+0.17, which give evidence of large-scale gravitational infall in the dense gas. From the millimetre and far-infrared data, the clump has a mass of similar to 2 x 104 M-circle dot, luminosity of similar to 2-3 x 104 L-circle dot and diameter of similar to 0.9 pc. From radiative transfer modelling, we derive a mass infall rate of similar to 3.4 x 10-2 M-circle dot yr-1. If confirmed, this rate for gravitational infall in a molecular core or clump may be the highest yet seen. The near-infrared K-band imaging shows an adjacent compact H ii region and IR cluster surrounded by a shell-like photodissociation region showing H-2 emission. At the molecular infall peak, the K imaging also reveals a deeply embedded group of stars with associated H-2 emission. The combination of these features is very unusual, and we suggest that they indicate the ongoing formation of a massive star cluster. We discuss the implications of these data for competing theories of massive star formation., OXFORD UNIV PRESS
Monthly Notices of the Royal Astronomical Society, Feb. 2010, [Reviewed]

Simulation of the Optical System for the ASTRO-G Offset Cassegrain Antenna
K. Kimura; T. Toshikawa; N. Shiroyama; A. Kurozumi; T. K. Ojima; Y. Abe; Y. Yonekura; H. Ogawa; H. Ujihara; Y. Murata; M. Tsuboi; T. Kasuga, We are developing the satellite (ASTRO-G) for the space VLBI mission, called VSOP-2 (Hirabayashi et al. 2004). This system will have an offset cassegrain antenna, and the three multi-mode feed horns (8, 22, 43 GHz bands) will be chosen by the Cassegrain focus position. We are designing the antenna optics of the three band receivers by using the GRASP physical optics software package on simulated feed configurations. The result of these simulations shows low cross-polarization level, a good radiation pattern, and the antenna efficiencies are 63-68 percent in these bands, assuming a perfect reflector. In this paper, we present these results of simulation of ASTRO-G antenna optics., ASTRONOMICAL SOC PACIFIC
APPROACHING MICRO-ARCSECOND RESOLUTION WITH VSOP-2: ASTROPHYSICS AND TECHNOLOGY, 2009, [Reviewed]

High-Resolution Studies of the Multiple-Core Systems toward Cluster-Forming Regions including Massive Stars
Hiro Saito; Masao Saito; Yoshinori Yonekura; and Fumitaka Nakamura, We present the results of C(18)O observations by the Nobeyama Millimeter Array toward dense clumps with radii of similar to 0.3 pc in six cluster-forming regions including massive (proto) stars. We identified 171 cores, whose radius, line width, and molecular mass range from 0.01 to 0.09 pc, 0.43 to 3.33 km s(-1), and 0.5 to 54.1 M(circle dot), respectively. Many cores with various line widths exist in one clump, and the index of the line width-radius relationship of the cores and the parental clump differs from core to core in the clump. This indicates that the degree of dissipation of the turbulent motion varies for each core in one clump. Although the mass of the cores increases with the line width, most cores are gravitationally bound by the external pressure. In addition, the linewidth and the external pressure of the cores tend to decrease with the distance from the center of the clump, and these dependencies may be caused by the inner H(2) density structure of the clump that affects the physical properties of the cores. Moreover, the number density of the cores and the number density of young (proto) stars have a similar relationship to the average H(2) density of the clumps. Thus, our findings suggest that the cluster is formed in the clump through the formation of such multiple cores, whose physical properties would have been strongly related to the H(2) density structure and the turbulent motion of the clump., IOP PUBLISHING LTD
Astrophys. J. Suppl. Series, Oct. 2008, [Reviewed]

THE SECOND SURVEY OF THE MOLECULAR CLOUDS IN THE LARGE MAGELLANIC CLOUD BY NANTEN. I. CATALOG OF MOLECULAR CLOUDS
Y. f*ckui; A. Kawamura; T. Minamidani; Y. Mizuno; Y. Kanai; N. Mizuno; T. Onishi; Y. Yonekura; A. Mizuno; H. Ogawa; M. Rubio, The second survey of the molecular clouds in the Large Magellanic Cloud in (CO)-C-12 (J = 1-0) was carried out by NANTEN. The sensitivity of this survey is twice as high as that of the previous NANTEN survey, leading to a detection of molecular clouds with M-CO greater than or similar to 2 x 10(4) M-circle dot. We identified 272 molecular clouds, 230 of which are detected at three or more observed positions. We derived the physical properties, such as size, line width, and virial mass, of the 164 GMCs that have an extent more than the beam size of NANTEN in both the major and minor axes. The CO luminosity and virial mass of the clouds show a good correlation of M-vir proportional to L-CO(1.1 +/- 0.1), with a Spearman rank correlation of 0.8, suggesting that the clouds are in nearly virial equilibrium. Assuming the clouds are in virial equilibrium, we derived an X-CO-factor of similar to 7 x 10(20) cm(-2) (K km s(-1))(-1). The mass spectrum of the clouds is fitted well by a power law of N-cloud(> M-CO) proportional to M-CO(-0.75 +/- 0.06) above the completeness limit of 5 x 10(4) M-circle dot. The slope of the mass spectrum becomes steeper if we fit only the massive clouds, e. g., N-cloud(> M-CO) proportional to M-CO(-1.2 +/- 0.2) for M-CO >= 3 x 10(5) M-circle dot., IOP PUBLISHING LTD
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Sep. 2008, [Reviewed]

A new 100-GHz band front-end system with a waveguide-type dual-polarization sideband-separating SIS receiver for the NRO 45-m radio telescope
Taku Nakajima; Takeshi Sakai; Shin'ichiro Asayama; Kimihiro Kimura; Masayuki Kawamura; Yoshinori Yonekura; Hideo Ogawa; Nario Kuno; Takashi Noguchi; Masato Tsuboi; Ryohei Kawabe, We developed a waveguide-type dual-polarization sideband-separating SIS receiver system of the 100-GHz band for the 45-m radio telescope at the Nobeyama Radio Observatory, Japan. This receiver is composed of an orthom*ode transducer and two sideband-separating SIS mixers, which are both based on a waveguide technique. The receiver has four intermediate frequency (IF) bands of 4.0-8.0 GHz. Over the radio frequency range of 80-120 GHz, the single-sideband receiver noise temperatures are 50-100 K, and the image rejection ratios (IRRs) are greater than 10 dB. We developed new matching optics for the telescope beam as well as new IF chains for the four IF signals. The new receiver system was installed in the telescope, and we successfully observed the 12CO, 13CO, and C18O emission lines simultaneously toward the Sagittarius B2 region to confirm the performance of the receiver system. The SSB noise temperature of the system, including the atmosphere, became approximately half of that of the previous receiver system. The IRRs of the two 2SB mixers were estimated from the 12CO and HCO+ spectra from the W 51 giant molecular cloud, resulting in > 20 dB for one polarization and > 12 dB for the other polarization. © 2008. Astronomical Society of Japan.
Publications of the Astronomical Society of Japan, 2008, [Reviewed]

A New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band　　　　　　　　　　　　　　　
Taku Nakajima; Masahiro Kaiden; Jun Korogi; Kimihiro Kimura; Yoshinori Yonekura; Hideo Ogawa; Shingo Nishiura; Kazuhito Dobashi; Toshihiro Handa; Kotaro Kohno; Jun-Ichi Morino; Shin'ichiro Asayama; Takashi Noguchi
Publ. Astron. Soc. Japan, Oct. 2007, [Reviewed]

Molecular Loops in the Galactic Center: Evidence for Magnetic Flotation　　　　　　　　　　　　　　　
Y. f*ckui; H. Yamamoto; M. Fujish*ta; N. Kudo; K. Torii; S. Nozawa; K. Takahashi; R. Matsumoto; M. Machida; A. Kawamura; Y. Yonekura; N. Mizuno; T. Onishi; A. Mizuno, 銀河系中心部で特異なループ構造を持つ分子雲ループを観測した。その結果、従来の超新星爆発とは異なる構造を明らかにした。それはは太陽表面で見られる「パーカー不安定」による現象を銀河系中心部に応用するものであり、サイズとしては太陽表面のループ現象より12桁ほど巨大なものであった。そこで、その構造を理論的に解明するために、銀河ループ構造のモデルの検証として二次元電磁流体シミュレーションを用い、そのモデルが正しいことを提唱した（担当：計算、解析、結果分析）
Science, 2006, [Reviewed]

A CO survey of the LMC with NANTEN: II. Catalog of molecular clouds
N Mizuno; R Yamaguchi; A Mizuno; M Rubio; R Abe; H Saito; T Onishi; Y Yonekura; N Yamaguchi; H Ogawa; Y f*ckui, From a (CO)-C-12 (J = 1-0) survey with the NANTEN telescope, we present a complete catalog of giant molecular clouds (GMCs) in the Large Magellanic Cloud. In total, 107 CO clouds have been identified, 55 of which were detected at more than 3 observed positions. For the 55 clouds, the physical properties, such as size, line-width, virial mass, and CO luminosity, are cataloged. From a statistical analysis of these quantities, we show that GMCs in the LMC are close to gravitational equilibrium. A comparison with Hi data indicates that most of the CO clouds are distributed in dense parts of 14 1 gas, whose H I column density is greater than 10(21) cm(-2). It is notable that the mass ratio of the molecular-to-atomic hydrogen of the lower radial velocity component of gas is similar to 0.2, which is a factor of 2 higher than Chat of the gaseous-disk component, similar to 0.1. Molecular clouds are apparently formed efficiently in the parent atomic clouds in the lower velocity component. The CO Arc, which is a few kpc scale ordered structure of CO clouds along the southern optical edge of the galaxy, corresponds well to the the lower velocity component of HI gas., OXFORD UNIV PRESS
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, Dec. 2001, [Reviewed]

Statistical study of dense cores in nearby star forming regions
K Tachihara; A Hara; T Onishi; A Mizuno; Y f*ckui; A Obayashi; Y Yonekura, We have carried out dense core surveys in (CO)-O-18 (J = 1-0) with NANTEN and the 4m radio telescopes in Nagoya University. In total 160 dense cores have been catalogued in nearby star forming regions, i.e., Taurus, L1333, Ophiuchus, Lupus, Corona Australis, and Chamaeleon (Onishi et al. 1996; Obayashi et al. 1998; Tachihara et al. 2000; Hara et al. 1999; Yonekura et al. 1999; Mizuno et al. 1999). This is one of the largest samples of the dense cores ever taken. We made a statistical study of star and cluster formation with the cores. The physical parameters of M, R, DeltaV, N(H-2), and n(H-2) of the (CO)-O-18 cores range 1.1-540 Mcircle dot, 0.07-0.45 pc, 0.32-1.94 km s(-1), (2.4-72) x 10(21) cm(-2), and (1.9-51) x 10(3) cm(-3), respectively. The total mass spectrum of the (CO)-O-18 cores is obtained, and we found that it is hardly expressed as a single power-law function and there seems to be turnover around M similar to 10Mcircle dot. In order to characterize the properties of the cares in terms of star forming activity, we categorized the cores into 3 groups as starless, star-forming, and cluster-forming cores according to the number of associated YSOs, and compared the physical parameters among them. Star-forming cores tend to be larger than starless cores in all the physical parameters except for DeltaV, and the cluster-forming cores are significantly larger than the others in all these parameters except for R. The virial analysis shaves that the star-forming cores have smaller virial ratios, M-Vir/M, i.e., more gravitationally bound, while the starless cores are not. The cluster-forming cores have moderate virial ratios. These facts imply that star-formation requires turbulence in the cores to be dissipated, and the formed clusters may enhance the turbulence. It seems that some of the cluster-forming cores will be dissipated in the near future., ASTRONOMICAL SOC PACIFIC
FROM DARKNESS TO LIGHT: ORIGIN AND EVOLUTION OF YOUNG STELLAR CLUSTERS, 2001, [Reviewed]

First results of a CO survey of the Large Magellanic Cloud with NANTEN; Giant molecular clouds as formation sites of populous clusters
Y f*ckui; N Mizuno; R Yamaguchi; A Mizuno; T Onishi; H Ogawa; Y Yonekura; A Kawamura; K Tachihara; KC Xiao; N Yamaguchi; A Hara; T Hayakawa; S Kato; R Abe; H Saito; S Mano; K Matsunaga; Y Mine; Y Moriguchi; H Aoyama; S Asayama; N Yoshikawa; M Rubio, A new survey of the LMC has been completed in 2.6 mm carbon monoxide emission with NANTEN. This survey has revealed 107 giant molecular clouds, the first complete sample of giant molecular clouds in a single galaxy at a linear resolution of similar to 40 pc. The cloud mass ranges from similar to 6 x 10(4) to 2 x 10(6) M., and the total molecular mass has been estimated to be 4-7 x 10(7) M. for a molecular column density of greater than or similar to 1.0 x 10(21) cm(-2), corresponding to 5-10% of the atomic mass. The molecular clouds exhibit a good spatial correlation with the youngest stellar clusters whose ages are less than or similar to 10 Myr, demonstrating that cluster formation is on-going in these clouds. On the other hand, they show little correlation with older clusters or with supernova remnants, suggesting that the molecular clouds are being rapidly dissipated in several Myrs, probably due to the UV photons of massive stars in clusters., OXFORD UNIV PRESS
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, Dec. 1999, [Reviewed]

A new derivation of the extinction-to-CO column density ratio in the Chamaeleon I dark cloud
T Hayakawa; A Mizuno; T Onishi; Y Yonekura; A Hara; R Yamaguchi; Y f*ckui, We have analyzed new datasets of (CO)-C-13 (J = 1-0)and (CO)-O-18 (J = 1-0) emission obtained with NANTEN and visual extinction, Av, derived from DENIS J-band observations in the Chamaeleon I dark cloud. The column densities of both molecular isotopes, N((CO)-C-13) and N((CO)-O-18), have been derived assuming LTE. Both N((CO)-C-13) and IV((CO)-O-18) are linearly correlated with Av in the range Av less than or similar to 10 mag. WE established the relationships N((CO)-C-13)(cm(-2)) = (1.2 +/- 0.1) x 10(15)Av(mag) + (0.7 +/- 0.3) x 10(15) and N((CO)-O-18)(cm(-2)) = (3.5 +/- 0.3) x 10(14)Av(mag) - (5.7 +/- 13) x 10(14). In a region of clustered T Tauri stars, however, both the AV-N(13CO) and Av-N((CO)-O-18) relationships are by a factor of similar to 2 steeper than the above. This may be mainly due to underestimates of the A(V) values, and the J-band star count might deserve a more careful examination for possible underestimates of associated young stars. Compared with the relationships for the other clouds, the slope of the A(V)-N((CO)-C-13) relationship is relatively shallower and that of the A(V)-N((CO)-O-18) relationship in a non-cluster forming region is slightly steeper. These facts suggest that cloud-to-cloud variation is significant in the A(V)-N(CO) relationships., OXFORD UNIV PRESS
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, Dec. 1999, [Reviewed]

Molecular clouds in the LMC observed with NANTEN II. Comparison with stellar clusters
R Yamaguchi; R Abe; A Hara; T Hayakawa; S Kato; A Kawamura; A Mizuno; N Mizuno; H Ogawa; T Onishi; H Saito; K Tachihara; KC Xiao; N Yamaguchi; Y f*ckui; Y Yonekura, We have made (CO)-C-12(J=1-0) observations of the LMC with the NANTEN millimeter-wave telescope and identified about 100 distinct giant molecular clouds (GMCs). A detailed comparison of the GMCs with stellar clusters and a UV image is discussed., ASTRONOMICAL SOC PACIFIC
NEW VIEWS OF THE MAGELLANIC CLOUDS, 1999, [Reviewed]

Molecular clouds in the LMC observed with NANTEN I. Physical properties of the clouds
N Mizuno; R Abe; A Hara; T Hayakawa; S Kato; A Kawamura; A Mizuno; H Ogawa; T Onishi; H Saito; K Tachihara; KC Xiao; N Yamaguchi; R Yamaguchi; Y f*ckui; Y Yonekura, Fully sampled (CO)-C-12(J=1-0) observations of the whole extent of the LMC have been made with a linear resolution of similar to 30 pc at a detection limit of N(H-2) = 2 x 10(21) cm(-2). In addition, several selected regions have been mapped with higher sensitivity corresponding to a detection limit of 1 x 10(21) cm(-2). Based on these results, a new estimate of the molecular mass in the LMC is presented., ASTRONOMICAL SOC PACIFIC
NEW VIEWS OF THE MAGELLANIC CLOUDS, 1999, [Reviewed]

Interaction between a massive molecular outflow and dense gas associated with IRAS 22142+5206
K Dobashi; Y Yonekura; Y Hayashi; F Sato; H Ogawa, We report results of (CO)-C-12, (CO)-C-13, and (CO)-O-18 (J = 1-0) observations made toward the luminous protostellar candidate IRAS 22142 + 5206 (similar to 16,100 L., at its kinematic distance of 4.5 kpc) using the 45 m telescope at Nobeyama Radio Observatory. We have discovered a massive CO outflow with a molecular mass of similar to 33 M., which is among the more massive outflows reported to date. The outflow lobes extend to over similar to 2 pc from the IRAS source. Dense gas (similar to 1140 M.) with an elliptical shape is also found around the source, with a velocity gradient of similar to 0.5 km s(-1) pc(-1) along its major axis. We find a cavity in the dense gas at positions where the CO outflow is prominent. We discuss the origin of the cavity, estimating the mechanical momentum and kinetic energy of the outflow, and conclude that the cavity was most likely created by the high-velocity jet of the outflow, which may have swept up part of the dense gas. We also carried out extensive (CO)-C-13 observations toward the IRAS source using the Nagoya 4 m telescope in order to reveal the overall distribution of molecular gas around the source. The results of these observations indicate that the IRAS source is embedded in a molecular cloud with a mass of 7300 M.., IOP PUBLISHING LTD
ASTRONOMICAL JOURNAL, Feb. 1998, [Reviewed]

Relations between star formation and the interstellar medium
Y f*ckui; Y Yonekura, We review observational results concerning star formation and dense molecular clouds, the interstellar medium most relevant to star formation process, as well as future prospects., SPRINGER
NEW HORIZONS FROM MULTI-WAVELENGTH SKY SURVEYS, 1998, [Reviewed]

A large-scale (CO)-C-13 distribution of the galaxy - A global view of star forming clouds
K Tachihara; Y Yonekura; A Kawamura; A Mizuno; H Ogawa; Y f*ckui, A large-scale (CO)-C-13 (J = 1-0) survey project is now on-going with two m millimeter-wave radio telescopes of Nagoya University. The purpose of this survey is to reveal the distribution of dense moleclar clouds, probable sites of star formation, along the Galactic plane and to investigate the physical conditions for star formation. This survey covers all area of l similar to 0 degrees - 230 degrees and b similar to -20 degrees - 20 degrees, corresponding to similar to 6060deg(2). This includes nearby star-forming regions such as Orion, Taurus, Cepheus, Cygnus, Serpens, Ophiuchus, and Lupus. The find the (CO)-C-13 distribution is highly clumpy. By using this dataset, we identified individual clouds at 3 sigma noise level and catalogued more than 1000 clouds having a wide mass range of similar to 10(1-4)M.. In this contribution, we briefly describe the results, focusing on the following three aspects; (1) mass spectra of star forming molecular clouds, (2) gravitational stabilities of these clouds, and (3) their star forming activities. At the end, we give a prospect on the southern sky survey to be made with the 4 m telescope recently installed at the Las Campanas Observatory in Chile., KLUWER ACADEMIC PUBL
IMPACT OF LARGE SCALE NEAR-IR SKY SURVEYS, 1997, [Reviewed]

OVERALL DISTRIBUTION OF DENSE MOLECULAR GAS AND STAR-FORMATION IN THE TAURUS CLOUD COMPLEX
A MIZUNO; T ONISHI; Y YONEKURA; T NAGAHAMA; H OGAWA; Y f*ckUI, We carried out a survey for dense molecular clouds in the Taurus complex in the (CO)-C-13 (J = 1-0) molecular emission at 2.7 mm wavelength with two 4 m millimeter-wave telescopes at Nagoya University. We obtained 37,720 spectra at a 1'.9 (l) x 2'.0 (b) grid spacing with a 2'.7 beam. Total molecular mass is estimated to be similar to 6800 M(.). There are three massive clouds, HCL2, B18, and L1495, and 13 small molecular clouds. Most of the clouds are connected with each other at a low intensity level. Among 94 young stellar objects (YSOs) identified in the Taurus complex, 59 are revealed to be associated with dense clouds having molecular column density greater than 3 x 10(21) cm(-2). Molecular gas of highest column density is associated with the youngest invisible protostellar objects, suggesting that star formation takes place in gas with high column density. Fifty of the 59 YSOs are associated with the massive clouds, and the remaining nine YSOs with the small clouds. Star formation efficiencies both in the massive and small clouds show similar values, suggesting that we may not neglect the contribution of small clouds toward global star formation. The basic structure of the molecular gas is filamentary, and we identified similar to 30 filamentary components distributed as a network. This suggests the importance of the process of gas condensation into a filamentary shape., IOP PUBLISHING LTD
ASTROPHYSICAL JOURNAL, Jun. 1995, [Reviewed]

A NEW LOOK AT THE DARK CLOUD L1251 - SENSITIVE OBSERVATIONS OF THE MOLECULAR-EMISSION
F SATO; A MIZUNO; T NAGAHAMA; T ONISHI; Y YONEKURA; Y f*ckUI, High-sensitivity observations in the (CO)-C-12, (CO)-C-13, (CO)-O-18, (HCO+)-C-13, and SiO lines have been made of the dark cloud L1251 in Cepheus. The (CO)-C-13 gas shows a cometary distribution with a U-shaped dense ''head'' having a highly ordered velocity gradient in the direction parallel to the minor axis of the cloud. Five (CO)-O-18 cores characterized by a mass of similar to 50 M. and a mean density of similar to 3 x 10(3) cm(-3) are embedded in the (CO)-C-13 cloud. Three of them have associated far-infrared sources, suggesting that stars have recently formed there. High angular resolution (CO)-C-12 observations have revealed a well-collimated compact outflow confined in the most massive, densest (CO)-O-18 core. Its driving source is embedded in a small (HCO+)-C-13 core With a mass of similar to 1-3 M.. A possibility is suggested that the U shape of the cloud and its well-defined velocity gradient may have resulted from some dynamical interaction with the ambient matter., UNIV CHICAGO PRESS
ASTROPHYSICAL JOURNAL, Nov. 1994, [Reviewed]

Unbiased surveys for dense cloud cores
Y f*ckui; A Mizuno; H Ogawa; K Dobashi; T Nagahama; JP Bernard; T Tsuboi; T Onishi; Y Yonekura, EDITIONS FRONTIERES
COLD UNIVERSE, 1994, [Reviewed]

(CO)-C-12 AND (CO)-C-13 OBSERVATIONS OF THE DARK CLOUD COMPLEX NEAR IC5146
K DOBASHI; Y YONEKURA; A MIZUNO; Y f*ckUI, A large scale survey of a dark cloud complex in the vicinity of IC5146 has been made in the (CO)-C-12(J = 1 - 0) and (CO)-C-13(J = 1 - 0) emission lines. 3000 spectra were obtained with 2' grid spacing for each line for an area of approximately 3-degrees X 2-degrees. Five CO clouds and fifteen (CO)-C-13 clumps are identified, and physical parameters such as mass, temperature, density of H-2 Molecules are derived for each clump. Total molecular mass of the dark cloud complex is estimated to be approximately 4500M. by assuming LTE, about 50% larger than that of the Taurus complex. The clumps are found to be nearly in virial equilibrium. There are 18 candidates for the young stellar objects in the region, and 13 of them are concentrated into two (CO)-C-13 clouds. Most active star formation is found in the most massive member of the complex having molecular mass of -2200M.. The cloud consists of two (CO)-C-13 clumps, whose masses are approximately 1 X 10(3)M., respectively, and is associated with six candidates for the young stellar objects. The velocity distribution of the entire cloud complex is characterized by a velocity gradient of 0.17 km s-1 pc-1 along the elongation of the complex over 2-degrees, in addition to a velocity gradient of approximately 0.27 km s-1 pc-1 orthogonal to the elongation at some places., AMER INST PHYSICS
ASTRONOMICAL JOURNAL, Oct. 1992, [Reviewed]