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Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia

Makin, Sally Victoria (2019) Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia. Doctor of Philosophy (PhD) thesis, University of Kent,.

Abstract

An unbiased, systematic survey for jets and outflows from young stars has been performed in two distinct and different regions in the Galactic plane. It utilised the 1 - 0 S(1) near-infrared line of molecular hydrogen (H2) to trace shock-excited emission, using data from the UKIRT Widefield Infrared Survey for H2 (UWISH2) survey. A total of 572 outflows were found in the high-mass star forming complex of Cygnus-X, and 98 in the low-mass regions of Auriga and Cassiopeia. Of these outflows found, 84% are entirely new discoveries, and now 40% of all the currently known H2 outflows are a result of the UWISH2 survey. The properties of the outflows were consistently measured and a large statistical sample has been built. Similarities and differences between the outflow populations in the two regions were explored in order to discover which properties are universal and which depend on local factors. In both regions, most outflows are located in isolated (60%) and not clustered environments, but those from clusters are longer and more luminous. Almost fifty new infrared cluster candidates have also been discovered as a result of this work, and the typical cluster is around 0.5 pc in diameter. About 10% of outflows form crossing pairs of outflows, and 40% of these show signs of precession compared to 20% in the general population. The outflow position angles are in agreement with a homogeneous distribution. Most of the outflows are driven by protostars (Class 0/I) rather than the more evolved young stellar objects (Class II), as determined using their mid-infrared magnitudes. The typical outflow has a length of < 0.4 pc, and is slightly asymmetric with one lobe around 30% longer than the other. The length distribution follows an exponential behaviour and there appears to be a maximum length. The typical outflow luminosity is faint (1×10$^?3$ Lsolar) and most of the outflows are driven by low or intermediate-luminosity protostars. The lobe luminosity ratios (the faint lobe over the bright lobe) are highly asymmetric in H2. There is a correlation between the length and luminosity of an outflow, and these do not depend on the evolutionary stage of the driving source. There is also a correlation between the luminosity of the driving source and the outflow luminosity, but the length distribution does not follow their behaviour. Therefore, the outflow lengths must also, to some extent, be governed by the density distribution of the local environment.

Item Type: Thesis (Doctor of Philosophy (PhD))
Thesis advisor: Froebrich, Dirk
Uncontrolled keywords: Galactic plane surveys astronomy star formation jets outflows
Divisions: Faculties > Sciences > School of Physical Sciences
Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
SWORD Depositor: System Moodle
Depositing User: System Moodle
Date Deposited: 05 Mar 2019 15:30 UTC
Last Modified: 03 Jun 2019 09:31 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/72857 (The current URI for this page, for reference purposes)
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