University of Illinois Urbana-Champaign

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

Stephens, Ian

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Ian_Stephens.pdf

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

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
Date of Ingest
2014-01-16T18:02:04Z
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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