The environments in which stars and circumstellar discs form

Abstract

In this thesis, images of a debris disc are used to examine the evidence for the presence of a Neptune-like planet around ε Eridani and detections of protoplanetary discs are used to investigate the evidence for star and future planet formation. A χ² analysis of the movement of clumps in the ε Eridani debris disc is presented using 850 μm SCUBA data taken over a 4 year period and compared with results from simulated data. A rotation is detected at the 2σ level and is faster than the Keplerian rate, consistent with theoretical models in which dust trapped in mean motion resonances tracks a planet orbiting the star at ≈26 AU. Future observations that could be taken with SCUBA-2 are also simulated and demonstrate that the true rotation rate cannot be recovered without the identification of the background sources aligned with the clumpy debris disc. Near and mid infrared observations are used to perform a survey of YSOs in the Rosette Molecular Cloud. Although triggering by compression of the molecular cloud by the expanding HII region at the centre of the Rosette Nebula is a possible origin for some of the recent star formation, the majority of the active star formation is occurring in already dense regions of the cloud not compressed by the expansion of the HII region. Mid-infrared data for W4 and SCUBA data for the star forming region AFGL 333 are also presented. A survey of YSOs reveals that whilst some young sources are coincident with the W4 loop, consistent with a scenario of triggered star formation in a swept-up shell, several young sources are found to be forming outside of this ring. The dust temperature and mass of AFGL 333 are estimated and the result implies a star formation efficiency of ~4% in the W4 loop.