Planetary nebulae in the southern sky

Abstract

This thesis investigates the data provided by the VST H-alpha Survey of the Southern Galactic Plane and Bulge (VPHAS+) to determine how the multi-wavelength data can be used to study planetary nebulae (PNe), and in particular, if the photometry it provides can be used to detect central star (CS) infra-red excess indicative of binarity. VPHAS+ photometry was examined, and the preliminary calibration found to be too imprecise for our needs. Therefore, we developed a new calibration process, referencing each VPHAS+ CCD to a second survey. We also calculated the expected colours of both main sequence stars and CS when viewed by VPHAS+, and the excess we would expect to detect from a range of CS binary systems. We compared this synthetic to observed data, using the expected colours to determine stellar spectral types, calculate reddenings, and detect CS infra-red excess. Using VPHAS+ data, we detected excess in four of eleven tested objects. We compared this to data of targeted CS observations, and found that in this case, the VPHAS+ photometry was more precise. We conclude that VPHAS+ data could be used to search for infra-red excess in a statistically significant number of stars, which in turn would allow the CS binary fraction to be calculated. Image data from VPHAS+ was visually examined to search for new PNe in the Galactic Bulge. We identified 25 new candidates, all of which were either very compact, or very faint, extended nebulae. CS candidates were identified for 14 of these PNe, with 7 deemed likely candidates. We calculated distances to each of these candidates, using a combination of the CS photometry and measurements using the H-alpha images of the nebulae.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Albert Zijlstra (Supervisor) & Timothy O'Brien (Supervisor)