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|Title: ||The earliest fragmentation in molecular clouds : and its connection to star formation|
|Authors: ||Smith, Rowan Johnston|
|Supervisors: ||Bonnell, Ian A.|
|Keywords: ||Star formation|
Core mass function
|Issue Date: ||21-Jun-2010|
|Abstract: ||Stars are born from dense cores of gas within molecular clouds. The exact nature of the
connection between these gas cores and the stars they form is an important issue in the field
of star formation. In this thesis I use numerical simulations of molecular clouds to trace the
evolution of cores into stars.
The CLUMPFIND method, commonly used to identify gas structures is tested. I find that
the core boundaries it yields are unreliable, but in spite of this, the same profile is universally
found for the mass function. To facilitate a more robust definition of a core, a modified clumpfind
algorithm which uses gravitational potential instead of density is introduced. This allows
the earliest fragmentation in a simulated molecular cloud to be identified. The first bound
cores have a mass function that closely resembles the stellar IMF, but there is a poor correspondence
between individual core masses and the stellar masses formed from them. From
this, it is postulated that environmental factors play a significant part in a core’s evolution.
This is particularly true for massive stars, as massive cores are prone to further fragmentation.
In these simulations, massive stars are formed simultaneously with stellar clusters, and
thus the evolution of one can affect the other. In particular, the global collapse of the forming
cluster aids accretion by the precursors of the massive stars. By tracing the evolution of the
massive stars, I find that most of the material accreted by them comes from diffuse gas, rather
than from a well-defined stellar core.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Physics & Astronomy Theses|
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