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ALMA observations of submillimeter H2O and SiO lines in Orion Source I

Published online by Cambridge University Press:  16 July 2018

Tomoya Hirota
Affiliation:
National Astronomical Observatory of Japan, Mitaka-shi, Tokyo 181-8588, Japan email: tomoya.hirota@nao.ac.jp
Masahiro N. Machida
Affiliation:
Kyushu University, Fukuoka-shi 819-0395, Japan
Yuko Matsushita
Affiliation:
Kyushu University, Fukuoka-shi 819-0395, Japan
Kazuhito Motogi
Affiliation:
Yamaguchi University, Yamaguchi-shi 753-8512, Japan
Naoko Matsumoto
Affiliation:
National Astronomical Observatory of Japan, Mitaka-shi, Tokyo 181-8588, Japan email: tomoya.hirota@nao.ac.jp Yamaguchi University, Yamaguchi-shi 753-8512, Japan
Mikyoung Kim
Affiliation:
Korea Astronomy and Space Science Institute, Daejeon 305-348, Republic of Korea National Astronomical Observatory of Japan, Oshu-shi, Iwate 023-0861, Japan
Ross A. Burns
Affiliation:
Joint Institute for VLBI ERIC, Postbus 2, 7990 AA Dwingeloo, The Netherlands
Mareki Honma
Affiliation:
National Astronomical Observatory of Japan, Oshu-shi, Iwate 023-0861, Japan
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Abstract

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We present observational results of the submillimeter H2O and SiO lines toward a candidate high-mass young stellar object Orion Source I using ALMA. The spatial structures of the high excitation lines at lower-state energies of >2500 K show compact structures consistent with the circumstellar disk and/or base of the northeast-southwest bipolar outflow with a 100 au scale. The highest excitation transition, the SiO (v=4) line at band 8, has the most compact structure. In contrast, lower-excitation transitions are more extended than 200 au tracing the outflow. Almost all the line show velocity gradients perpendicular to the outflow axis suggesting rotation motions of the circumstellar disk and outflow. While some of the detected lines show broad line profiles and spatially extended emission components indicative of thermal excitation, the strong H2O lines at 321 GHz, 474 GHz, and 658 GHz with brightness temperatures of >1000 K show clear signatures of maser action.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

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