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Does magnetic field matter during the earliest stages of star cluster formation?

   Cardiff School of Physics and Astronomy

About the Project

Stars light up every single galaxy across the Universe, 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, we do not know what triggers that collapse, whether it is driven by gravitational instabilities, turbulent compression, magnetic field diffusion, or some combination of all three. The turbulence (via the measurement of the width of spectral line emission) and gravity (via the measurement of gas masses) of interstellar molecular clouds are routinely characterised. However, magnetic fields are a lot more complicated to observe. But in the past few years, as the result of technological advancements, it has become easier to derive the direction of magnetic fields in cold interstellar clouds. This is done by observing the sub-millimetre polarisation emission of dust grains that pervade the interstellar medium. The direction of the polarised light directly tells you in which direction the magnetic field is in the plane-of-the-sky. Instruments like POL2 on the JCMT is at the forefront of such state-of-the-art observations. 

Recently, Peretto et al. (to be submitted) showed that that clumps, i.e. the progenitors of stellar clusters, are dynamically decoupled from their parent molecular clouds, probably as the result of their global collapse. However, it is unclear if this collapse finds its origin in the change of magnetic field properties.

In the context of this PhD project, the student will analyse brand new JCMT POL2 observations of a number of clumps (>10), characterise the magnetic field morphology in those. Morphology of the magnetic field in the larger scale molecular clouds will be determined by using Planck and GPIPS data. Connecting the different magnetic field datasets will allow us to determine whether or not the observed dynamical transition is matched by a transition in magnetic field properties which could be an indication that it is at the origin of the clump collapse.

In a second step, the student will characterise the correlations between the clump magnetic field directions and gas velocity gradients, both in the observations and numerical simulations of cloud evolution, with the goal of determining whether magnetic fields are entrained by gravity in the densest regions or not. 

The student taking on this PhD will find themselves at the forefront of star formation research and will be in an excellent position to take full advantage of future polarisation instrumentations that will be developed in the next few years.


The typical academic requirement is a minimum of a 2:1 a relevant discipline.

Applicants whose first language is not English are normally expected to meet the minimum University requirements (e.g. 6.5 IELTS) (

How to apply

Applicants should apply to the Doctor of Philosophy in Physics and Astronomy.

Applicants should submit an application for postgraduate study via the Cardiff University webpages ( including:

• your academic CV

• a personal statement/covering letter

• two references, at least one of which should be academic

• Your degree certificates and transcripts to date (with certified translations if these are not in English).

In the "Research Proposal" section of your application, please specify the project title and supervisors of this project.

This project is only available to self-funded students, please can you include your funding source in the "Self-Funding" section.

Funding Notes

Please note that bench fees may be charged in addition to tuition fees for this project. This will be confirmed as part of any formal offer for this project.


Peretto et al. 2013, A&A, 555, 112
Ward-Thompson et al., 2017, ApJ, 842, 66
Tang et al., 2019, ApJ, 878, 10
Pattle et al., 2022, Protostar & Planets VII, conference proceeding
Peretto et al (to be submitted) can be provided upon reasonable request

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