Young system development in a cometary globule: A study of infrared and radio observations of the circumstellar disk around AT Pyx

Aims: To understand the formation of planetary systems, it is necessary to observe and study systems at different evolutionary stages and in different environments. This project focuses on the AT Pyx system, a protoplanetary disk-hosting young star located in a cometary globule in the Gum Nebula. This is a unique system in that its formation environment differs greatly from the types of environments disks have generally been observed in to date. Using a host of different sources of data this project aims to infer what processes are at play in the disk and what the prognosis may be for planet formation. Methods: Using data from the VLT’s (Very Large Telescope) instruments XSHOOTER, ESPRESSO and - most prominently - SPHERE along with data from ALMA (Atacama Large Millimetre-submillimetre Array), a variety of measurements (geometric, photometric and otherwise) are made to characterise the observed disk features such as spiral arms and eccentricity. Mapping of the velocity components is also undertaken using the ALMA gas line data to characterise disk orientation and determine likelihood that the system is experiencing a late-stage infall event. Results: The disk is measured to have a position angle of ∼ 22◦ and an inclination of ∼ 42.5◦. The disk is found to be eccentric with tentative e ≈ 0.626 when deprojected according to literature values for disk height profile. Under the assumption that the formation of a planet is wholly responsible for the primary and secondary spiral arms, the mass of such a planet is found to range between 0.02 and 3 Jupiter masses. Measurement of the velocities associated with nearby globule cloud material returns appropri- ate velocities for a late-stage infall event. Far-ultraviolet field strength at AT Pyx’s location is found to be low in comparison to other surveyed disks. It is also found that AT Pyx is possibly a binary system. Conclusions: AT Pyx was the first disk within a cometary globule to be spatially resolved, and is now the first such disk to be investigated to this extent. The work of this project could potentially be a first step into the study of disks in the moderate-FUV environment of the Gum Nebula and its globules. Further work involving the high-resolution imaging of AT Pyx and other such disks is recommended and it is suggested that AT Pyx is an excellent candidate target for the forthcoming ELT. A sample of other disks for study in the same region both inside and outside cometary globules and molecular clouds is presented.

Publisher

University of Galway

Rights

CC BY-NC-ND

cbn

Collections

University of Galway Theses (Research Masters Theses)