Planetary nebulae with ALMA and the SKA

Abstract

This thesis focuses on the study of planetary nebulae with the radio interferometers ALMA and the SKA. In the first part of the project, we present and analyse 12CO, 13CO and C18O ALMA observations of the C1 globule inside the Helix nebula in order to determine its physical properties. Our findings confirm the molecular nature of the globule. The derived 12C/13C and 16O/18O ratios are not in agreement with the isotopic ratios of carbon-rich AGB stars, calling into question the chemical nature of the Helix nebula. We obtain a molecular mass of about 2 x10-4 Msol for the C1 globule. The origin of the tail is discussed. Our findings show that the most probable model appears to be shadowing. The kinematics and molecular morphology of the knot are not consistent with a wind-swept model and the photoevaporation model alone is not enough to explain the nature of the globule. We propose an integrated model where the effects of the photoevaporation, the stream and shadowing models are all considered in the tail shaping process. In the second part of the thesis, observational simulations of the planetary nebula NGC 2440 are performed with the profile SKA simulator, using radio continuum VLA data of NGC 2440 as input. We observe that the maps generated with the SKA with a short integration time are of the same quality as VLA maps with about 9-hour exposure time, showing the strong potential of the SKA for planetary nebulae detection and morphological study.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Albert Zijlstra (Supervisor) & Keith Grainge (Supervisor)