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A Submillimetre Survey of Clustered Low-Mass Star Formation
Emily I. Curtis

PhD Thesis, University of Cambridge, 2009


This thesis presents a new survey of the kinematics of clustered, low-mass star formation. The
survey uses HARP, a new submillimetre heterodyne array at the James Clerk Maxwell Telescope
(JCMT), to map the J = 3 - 2 rotational transitions of CO and its isotopologues 13CO and
C18O across 630 sq. arcmin of the Perseus molecular cloud, in four regions: NGC1333, IC348,
L1448 and L1455.

An algorithm to account for variable calibration across the array is developed, which can be used
to remove prominent artefacts in HARP data towards molecular clouds. A new catalogue of
850 micron SCUBA clumps is identified using two automated algorithms, clfind and GaussClumps.
The clumps found are gravitationally bound with a mass distribution comparable to the stellar
initial mass function. However, many previously reported properties heavily depend on the
algorithm used to identify the clumps' emission. The C18O J = 3 - 2 linewidths of these
clumps are supersonic, varying according to the clump age and environment and are smaller
than predicted currently by gravoturbulent models. Localized velocity gradients are identified
across many of the SCUBA clumps, which I interpret as signs of core rotation. The resultant
angular momentum distribution is consistent with the smallest momenta previously observed
in similar studies. Clumps of C18O and 13CO gas are also identified using clfind, additional
clumps with no continuum counterparts are not bound, but do obey Larson's laws.
The 13CO/C18O abundance is measured to be around 10 in most of Perseus, with typical gas
excitation temperatures of 5-30 K. Radiative transfer modelling indicates that in a typical starforming
core, the C18O J = 3 - 2 line is very weak until the central densities
are n & (2 - 5) в 10^5 cm^-3.

These data are one of the largest surveys of molecular outflows ever undertaken. Class 0 protostars
appear to drive longer, faster, more forceful and massive outflows than class I protostars.
Outflows become less powerful as they age, possibly as their mass accretion rates reduce. The
total contribution of momentum and energy by outflows could drive turbulence or even disperse
the individual regions.

Finally, technical work is described, detailing the commissioning of HARP and upgrade of the
JCMT for use as part of the eSMA, a new collaborative interferometer facility.