Adding Fuel to the Fire: Investigating Star and Planet Formation through Observations of Episodically Accreting Protostars and Gapped Protoplanetary Disks

dc.contributor.authorFrancis, Logan
dc.contributor.supervisorJohnstone, D. of Physics and Astronomyen_US of Philosophy Ph.D.en_US
dc.description.abstractThe advent of the Atacama Large Millimeter/sub-millimeter Array (ALMA) has provided a revolutionary depth and clarity to our view of forming stars and planets. With these improved capabilities, observations can provide novel evidence to shed light on a variety of fundamental open questions which I consider in this dissertation. The assembly of mass to form stars occurs mostly through the accretion of material from a circumstellar disk, a process which is likely extremely time variable. Our knowledge of variable accretion in the youngest protostars is poorly constrained, however, as they are not visible at optical and shorter wavelengths. I have thus analyzed observations of variable protostars monitored with sub-mm/mm interferometers, which can measure the thermal response of the dust to accretion changes and probe the structure of the protostellar environment. %add one more sentence saying something about toy models? The quality of data required by these observational programs is only possible with the improved relative flux calibration strategies I have developed, which provide an unprecedented level of calibration accuracy. In later stages of a young stellar object's evolution, planets are expected to form from the condensation of material in the disk. The transition disk class of objects contain prominent gaps in their dust distribution, which may be the signpost of forming planets or disk dispersal. Using the exquisite resolution possible with ALMA, I have performed the first systematic study of inner disks within transition disk gaps, providing new constraints for theories of planet formation, planet-disk interaction, and dust evolution. The enigmatic transition disk of the DM Tau T Tauri star is highly turbulent and accreting at an unusually high rate, which is difficult to reconcile with past observations of transition disks that have shown their gaps to be highly depleted of gas. Using ALMA observations of gas-tracing molecules and thermochemical modelling, I have identified a particularly shallow gas gap in DM Tau and evaluated planet-disk interaction and photoevaporative dispersal models as origins of the dust gap.en_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectstar formationen_US
dc.subjectplanet formationen_US
dc.subjectsubmm/mm astronomyen_US
dc.subjectradio interferometryen_US
dc.subjecttransition disksen_US
dc.titleAdding Fuel to the Fire: Investigating Star and Planet Formation through Observations of Episodically Accreting Protostars and Gapped Protoplanetary Disksen_US


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