From gas and dust to protostars: addressing the initial stages of star formation using observations of nearby molecular clouds
Date
2017-12-11
Authors
Mairs, Steve
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Though there has been a considerable amount of work investigating the early
stages of low-mass star formation in recent years, the general theory is only broadly
understood and several open questions remain. Specifically, the dominant physical
mechanisms which connect large-scale molecular cloud structures, intermediate-scale
filamentary gas flows, and small-scale collapsing prestellar envelopes in the interstellar
medium are poorly constrained. Even for an individual forming protostar, the evolution
of the mass accretion rate from the envelope onto the central object is debated
with little observational evidence to help guide the theoretical framework. In addition,
with the development of new technology such as the continuum imaging instrument
in operation at the James Clerk Maxwell Telescope (JCMT), the Submillimetre Common
User Bolometer Array 2 (SCUBA-2), the best practices for data reduction and
image calibration for ground-based, submillimetre wavelength observations are still
being investigated.
In this dissertation, I address facets of these open questions in five main projects
with an overarching focus on the flow of material from the largest to the smallest
scales in a molecular cloud. By performing synthetic observations of a numerical simulation
of a turbulent molecular cloud, I investigate the nature of prestellar envelopes
and find evidence of larger mass reservoirs that form filamentary structures and feed cluster formation. Then, after robustly investigating and suggesting improvements for
ground-based, submillimetre data reduction techniques, I continue to probe the connection
between larger and smaller scales by characterising structure fragmentation
in the Southern Orion A Molecular Cloud from the perspective of 850 m continuum
data. Finally, I follow star forming material to even smaller scales by exploring the
evolution of the mass accretion rate onto individual protostars. This examination
has required designing and implementing unprecedented spatial alignment and flux
calibration techniques at 850 m. Using these newly calibrated images, I am able
to identify several candidate sources that show evidence for submillimetre variability,
suggesting changes in protostellar accretion rates over several year timescales.
Description
Keywords
star formation, astronomy, variability, submillimetre, james clerk maxwell telescope, dissertation, data reduction, scuba-2