The environmental impact of high- and low-mass stars: from formation to main sequence

Stephens, Ian

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https://hdl.handle.net/2142/46773 Copy

Description

Title

The environmental impact of high- and low-mass stars: from formation to main sequence

Author(s)

Stephens, Ian

Issue Date

2014-01-16T18:02:04Z

Director of Research (if dissertation) or Advisor (if thesis)

Looney, Leslie W.

Doctoral Committee Chair(s)

Looney, Leslie W.

Committee Member(s)

• Chu, You-Hua
• Crutcher, Richard M.
• Wong, Tony

Department of Study

Astronomy

Discipline

Astronomy

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Star Formation
• Magnetic Fields
• Large Magellanic Cloud
• Massive stars
• Protostars
• HII Regions
• Interstellar Medium (ISM)
• Young Stellar Objects
• Outflows

Abstract

Throughout the entire lifetime of a star, it continuously alters the environment. Diverse processes are involved which complicates studies of stellar interaction. This thesis focuses on two different physical phenomena associated with stars: (1) the interplay of magnetic fields and collapsing clouds, and (2) the effects of radiation from massive stars. We first compare polarization measurements of 52 Galactic star-forming regions with their locations in the Galaxy. In particular, we find that there is no correlation between the average magnetic field direction of star-forming molecular clouds and the Galaxy, indicating that star formation may eventually become its own process independent of the Galaxy. Secondly, we observe the coupling of the magnetic field with the low-mass protostar L1157-mm by creating polarimetric maps at resolutions from ~300 to 2500 AU. The inferred magnetic field lines show a well-defined hourglass morphology centered about the core -- only the second of such morphology discovered around a low-mass protostar. Next, we focus on radiation from massive stars in the Large Magellanic Cloud. We first present a survey of HII regions around massive young stellar objects (YSOs) and explore numerous relationship between parameters measured through observations of free-free and infrared emission. In particular, we find that YSO mass is a crucial consideration when exploring almost any relationship. Finally, we analyze how massive stars process dust in two classical HII regions and two superbubbles. We find that PAH emission is highest in the presence of molecular clouds with a low radiation field and that emission from very small grains are particularly high at locations where the radiation field is very strong.

Graduation Semester

2013-12

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http://hdl.handle.net/2142/46773

Copyright and License Information

Copyright 2013 Ian Stephens

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