Numerical simulations of triggered star formation

Balfour, Scott K. 2016. Numerical simulations of triggered star formation. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Feedback from massive stars is thought to be very important in regulating star formation on a range of scales. However, it is not clear if this feedback acts in a positive way by triggering star formation, or negatively by terminating it. In this thesis we investigate what role feedback plays in determining both the structure of molecular clouds and the rate of star formation, using Smoothed Particle Hydrodynamics. We begin by looking at how the evolution of an HII region is dependent on the amount of ionising radiation the exciting star produces. We then go on to explore the stellar populations created by cloud-cloud collisions and assess their ability to form high mass stars capable of producing large amounts of feedback. We then model the HII regions of these stars and determine what impact these have on star and structure formation. We find that there is a minimum stellar mass required to produce enough feedback to maintain an HII region. Below this value an HII region will either not form, or form and then implode. Above this value the HII region will act as a traditional HII region, and expand. When two clouds collide we �nd that they produce a shock compressed layer which forms �lamentary structures. The arrangement of these �laments is highly dependent on the collision velocity. Low velocity collisions produce a hub and spoke system in which competitive accretion dominates and produces a few very massive stars and a plethora of low mass stars. High velocity collisions produce lamentary networks that resemble a spider's web. In these spider's webs the stars form at nodes where multiple �laments meet. These nodes act as small local sites for star formation and form either a single, or small collection of stars. As a result stars formed in these systems tend to have a characteristic mass and there is less low mass or high mass star formation. However, we do find that eventually stars capable of producing signi�cant feedback form in all simulations. We model the HII regions of these stars and �find that they very quickly terminate star formation. They also produce very interesting bi-polar HII regions that are diffi�cult to interpret when viewed from some directions.

Item Type:	Thesis (PhD)
Date Type:	Publication
Status:	Unpublished
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Uncontrolled Keywords:	star formation, massive stars, stellar feedback
Funders:	STFC
Date of First Compliant Deposit:	27 September 2016
Last Modified:	12 Jun 2019 02:55
URI:	https://orca.cardiff.ac.uk/id/eprint/94927

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