Each year we incorporate final year students into the group in order for them to undertake an independent research project in star and planet formation. Below are descriptions and figures from a handful of projects completed by MPhys students at Leeds in the last few years.
Connecting low- and high-mass star formation: the intermediate-mass protostar IRAS 05373+2349 VLA 2 – Greg Brown
The aim of the master’s year project was to highlight the known young, intermediate-mass protostar within the IRAS 05373+2349 embedded cluster as a good case study for star formation in the intermediate-mass regime. Much more is known about the formation of low- and high-mass stars, with the major research focus now being on understanding whether high-mass stars can form under a similar, although scaled-up, mechanism as in the low-mass regime. On the other hand, some suggest that high-mass stars should reach a limit in how much mass they can accrete due to the extreme environments around these types of stars. Yet, stars with much higher masses than this limit have been observed, leading to new formation mechanisms being put forward. Intermediate-mass stars are said to be a bridge between the two regimes, showing smooth transitions in various phenomena such as outflow energetics. Further research in the intermediate regime will likely be crucial in providing the answers to these questions.
Characterising the Morphology of Previously Unresolved Ultracompact HII Regions – James Miley
Young massive stars make their final formation steps whilst still enveloped in a dense molecular cloud, obscuring our view of the object at wavelengths shorter than infrared. The central object will begin to produce a flux of UV photons; these are energetic enough to be able to ionise the hydrogen in the dense envelope via free-free emission, producing what is known as a HII region. The HII region therefore acts as a signpost to astronmers that the central object has ‘switched on’ its UV photon flux and that a massive star has recently been formed at this location. When looking at massive stars in our galaxy – anything over eight times the size of our own Sun – the UV flux creates an ultracompact HII region (UCHII) that can only be detected using state of the art interferometers.
This project used data from the Very Large Array (VLA) in New Mexico to pick up such radio signals. UCHIIs are easily shaped and moulded by their environment and so not only do we have a signpost of massive star formation but by analysing the apparent morphology of the emission we can also begin to characterise the properties of the local environment. This can give us clues as to the dominant processes at work when forming UCHII regions but also what environments are encouraging massive star formation.