Why is the Universe getting cleaner by the day? Modelling dust, gas and metals in high redshift galaxies using BEDE

About the Project

High redshift galaxies discovered using submillimetre surveys of the sky (so-called submillimetre galaxies) are likely ancestors of present-day massive early-type galaxies. Thanks to the Herschel Space Observatory, astronomers have discovered many extreme star forming systems at redshifts 3-5 implying enormous gas reservoirs.

Recent observations hint that the mass of gas in these submillimetre galaxies is larger than the total mass of the galaxy derived from the galaxy dynamics. This result is not physically possible. The metal content of these galaxies is also estimated to be far higher than the levels measured in galaxies today, despite their being less time for the metals to build up. By modelling the evolution of gas, stars, metals and dust in these extreme star-forming systems we proposed two suggestions to explain these observations. First, the conflict between the total mass and the mass of interstellar gas may simply be due to an overestimation of the gas to dust ratio currently used to derive gas masses in high redshift galaxies. This has enormous consequences for determining how high redshift galaxies evolve. Second, we proposed that the high metallicity content is simply a consequence of the galaxies forming more massive stars than expected compared to galaxies today, ie they require a top-heavy initial mass function.

The project will use an established chemical evolution model and apply it to high redshift galaxies discovered as part of the Herschel ATLAS survey – one of the largest surveys undertaken with the Herschel Space Observatory. One important aspect currently missing from the model is the ability to trace the evolution of various heavy elements in the gas phase to compare with complimentary observations from the Atacama Large Millimetre Array (ALMA). In our previous work, we used simple model comparisons, however in this project, we will use a form of the model which includes Bayesian inference when comparing with galaxy survey data.

During the PhD, student(s) will learn data analysis methods, how to conduct independent research and they will gain skills in presentations and coding (python, github). Student(s) will have opportunities to attend and present their work at conferences. They will have access to a range of training events run by the University and have the opportunity to be part of a vibrant School, recently awarded the Athena Swan Silver as recognition for its efforts in equality, diversity and inclusion.

For more information, or if there are any questions, please contact Professor Haley Gomez GomezH@cardiff.ac.uk

The typical academic requirement is a minimum of a 2:1 physics and astronomy or a relevant discipline.

Applicants whose first language is not English are normally expected to meet the minimum University requirements (e.g. IELTS 6.5 Overall with 5.5 minimum in sub-scores).

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
• Your degree certificates and transcripts to date including certified translations if these are not in English
• a personal statement/covering letter
• two references, at least one of which should be academic. Your references can be emailed by the referee to physics-admissions@cardiff.ac.uk

Please note: We are do not contact referees directly for references for each applicant due to the volume of applications we receive.

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

In the funding section, please select that you will be self-funded or include your own sponsorship or scholarship details.

Once your application is submitted, we will review it and advise you within a few weeks if you have been shortlisted for an interview.

Funding Notes

This project is offered for self-funded students only, or those with their own sponsorship or scholarship award.