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CO Observations Toward IRAS 07280-1829 and Its Related Clouds

적외선원 IRAS 07280-1829와 이와 관련된 분자운의 CO분자선 관측연구

  • Received : 2011.07.16
  • Accepted : 2011.08.21
  • Published : 2011.08.31

Abstract

We present results of CO observations toward an infrared (IR) source, IRAS 07280-1829, and its possibly related molecular clouds. The physical parameters of this IR source such as its infrared slope (${\alpha}$=16) of the Spectral Energy Distribution and bolometric temperature (145 K) indicate that it is an embedded protostar. Its luminosity is ${\sim}2.9{\times}10^4L_{\odot}$, typical of a massive star. The CO profile toward IRAS 07280-1829 has broad wing components, implying a possible existence of CO outflow. The excitation temperature and mass of a molecular cloud (Cloud A) which is thought to harbor the IR source are estimated to be 9~22 K and ~180 $M_{\odot}$, respectively, indicating the Cloud A is a typical infrared-dark cloud. Its LTE mass is found to be much smaller than its virial mass by more than a factor of 10 which is inconsistent with the fact that a protostar recently formed exists in the Cloud A. This may suggest that the environment of the cloud where the IR source is forming is dominant of turbulence and/or magnetic filed, making its virial mass estimated unusually high.

본 논문에서는 IRAS 07280-1829 적외선원과 이를 둘러싸고 있는 분자운에 대해 수행된 $^{12}CO$$^{13}CO$ 1-0 분자선 관측결과와 기존의 적외선 자료를 이용하여 이 적외선원의 생성환경에 관해 연구하였다. 관측자료로부터 얻어진 적외선원의 파장별 에너지분포의 기울기(${\alpha}$=1.16)와 복사온도(145 K), 그리고 광도(${\sim}2.9{\times}10^4L_{\odot}$)는 이 적외선 천체가 CLASS I형의 중량급원시성임을 의미한다. 이 적외선원방향에서 관측된 두 CO 분자선에서 보이는 넓은 속도 성분은 분자분출류의 존재를 암시한다. 적외선원을 감싸고 있으리라 짐작되는 분자운A에서 측정된 여기온도는 9-22 K, 질량은 약 ~180 $M_{\odot}$인 것으로 보아 이 분자운이 전형적인 적외선 암흑분자운(Infrared-dark clouds)의 물리적 특성을 가짐을 보았다. 이 분자운의 질량은 비리알 질량보다 10배 이상 작은 값으로 계산되었는데 이것은 여기에 어린 원시성이 이미 생성되고 있다는 관측사실에 모순된다. 이는 아마도 분자운A가 교란운동(turbulence) 혹은 강한 자기장에 의해 지배되는 환경 가운데에 중량급원시성 IRAS 07280-1829을 생성하고 있음을 의미하는 것 일수도 있는 것으로 해석하였다.

Acknowledgement

Supported by : 한국연구재단

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