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

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Astronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Stephens, Ian

Contributors dc:contributor

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

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

Statement dc:rights

• Copyright 2013 Ian Stephens

Language dc:language

en

Handle dc:identifier

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

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/46773