How fast are star-forming clouds collapsing?

Stars are the candles of the Universe, they light up every single galaxy allowing us to study their structure across the cosmos. Despite their importance, there are still many aspects of the star formation process that remain poorly constrained.
We know that stars form as the result of the fragmentation and collapse of large interstellar clouds of cold molecular gas. However, even today, we still do not know what fraction of a star-forming cloud mass is indeed in a state of collapse. We also do not know how fast that collapse might be, whether it is a rather slow contraction or a rapid close-to-free-fall collapse.
One recurrent argument in favour of a slow evolution of star-forming clouds is that the few cloud infall velocities that have been measured so far are ~10 times smaller than those that we would expect if the gas were to be free-falling. However, in all circumstances, the way the free-fall velocities are estimated in these comparisons is flawed, mixing up measurements taken at different times of a cloud evolution.
In the context of this PhD project, the student will develop a method that will allow us to derive cloud free-fall velocities at any time of a cloud evolution. This method will be validated with numerical simulation of cloud collapse, and then used to determine how fast the clouds for which an infall velocity has been obtained are really collapsing.
In a second stage of the PhD, the student will build-up on their previous results by using machine learning technique in order to derive infall velocities of clouds in a systematic way. This will be achieved by analysing large sets of numerical simulations of cloud evolution, for which synthetic observations will be constructed. Using those as training datasets for deciding whether or not a cloud is collapsing, the student will then analyse state-of-the-art observational data (such as ALMA) of star-forming regions in order to apply the newly developed technique.

This project will be funded by the STFC.
Applicants should apply to the Doctor of Philosophy in Physics and Astronomy with a start date of 1st October 2021.

How to Apply:

Applicants should submit an application for postgraduate study via the Cardiff University webpages (https://www.cardiff.ac.uk/study/postgraduate/research/programmes/programme/physics-and-astronomy) including:

• an upload of your CV
• a personal statement/covering letter
• two references
• Current academic transcripts

Applicants should select Doctor of Philosophy, with a start date of October 2021.

In the research proposal section of your application, please specify the project title and supervisors of this project. If you are applying for more than one project, please list the individual titles of the projects in the text box provided. In the funding section, please select ’I will be applying for a scholarship/grant’ and specify that you are applying for advertised funding from the STFC. Shortlisted candidates will be invited to attend an interview in February.

Entry requirements:

Candidates should have obtained, or be about to obtain a First or Upper Second Class UK Honours degree in Physics, or a related subject, Alternatively, applicants with equivalent qualifications gained outside the UK will also be considered. Applicants with a Lower Second Class degree will be considered if they also have a Master’s degree.

Applicants whose first language is not English are normally expected to meet the minimum University requirements (e.g. 6.5 IELTS)
Please see our English Language Requirements guidance (https://www.cardiff.ac.uk/study/international/english-language-requirements) for more details.