Overview
Background
I am a Senior Research Fellow in Cosmology based in the School of Mathematics and Physics. I work on making maps of the positions and motions of millions of galaxies in our Universe to uncover how it has evolved since the Big Bang. Current observations suggest 95% of our Universe consists of ellusive Dark Matter and Dark Energy; we can detect these by the influence they have on the light from galaxies, stars and that permeates the background Universe itself, but they don't emit light themselves and we have no idea yet what they are. My research seeks to uncover these using the largest galaxy surveys in the world.
I have been involved in planning, carrying out, and analysing a large number of these surveys. I currently working groups in the American-led Dark Energy Spectroscopic Instrument (DESI) project, the WALLABY survey based in Western Australia, and the 4MOST Hemisphere Survey (4HS) which will be carried out from Chile. Combined, these will produce the most detailed maps of galaxy positions and motions ever created --- over 40,000,000 unique galaxies!
My personal research makes use of state-of-the art computing techniques to simulate the distributions of these galaxies, their properties, and how fast they are moving. I then analyse these distributions using different statistical techniques and compare to the real data. The properties of Dark Matter and Dark Energy and all the other things that make up our Universe can then be extracted by modelling these statistics with theoretical models, or looking for discrepancies between the simulations and the data. My hope is that by doing so, we are currently on the cusp of uncovering something fundamental about how the Universe came to be the way it is today, and what will happen to it in the future.
Academic Background
- Undergraduate: MPhys 1st Class Honours - University of Sussex, 2008-2012
- Postgraduate: PhD - University of Portmouth, 2012-2016
- Research Associate - University of Western Australia, 2015-2019
- Research Fellow in Cosmology - University of Queensland, 2019-
Availability
- Dr Cullan Howlett is:
- Not available for supervision
- Media expert
Fields of research
Qualifications
- Doctor of Philosophy, University of Portsmouth
Research interests
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Testing gravity using galaxy positions and motions
One compelling way to explain dark matter and dark energy is that our current theory of gravity (General Relativity) doesn't work on scales much larger than the Solar system. One of my interests is developing different models and understanding how they can be proven or disproven with galaxy properties.
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Fast simulations of large scale structure
Current state of the art simulations are able to simulate the distributions of billions of galaxies, but these are very slow and can take weeks to run on the largest supercomputers. I'm interested in new approximate ways for generating these simulations or cool computational techniques such as machine learning, that can be run in a fraction of the time, or on fewer processors.
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New statistical methods for analysing distributions of galaxies
In addition to theoretical developments, I'm interested in looking for new statistical ways to use the galaxy data we have to give us insight into the Universe.
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Gravitational waves
Gravitational waves, first detected in 2015 are the new hot topic in physics and offer interesting ways to test cosmology. I'm interested in creating simulated catalogues of gravitational waves and using these to working out what cosmological insights gravitational waves can bring
Research impacts
The nature of dark matter and dark energy is the biggest question in modern science. Are they particles we haven't discovered yet, or perhaps a misunderstanding of our fundamental pillars of physics (Einstein's theory of General Relativity or Quantum Mechanics). We don't know, but the answer is out there, and it's likely profound. It will change everything we know about physics, and with this understanding could come unimagined new ideas and technologies. In the same way that our modern understanding of the atom and electromagnetism has lead to the technologic marvels we have today that would seem wonderous to someone 200 years ago, in 200 years from now who knows where an understanding of the Dark parts of our Universe will take us.
In order to unlock this information, cosmologists including myself have to come up with new techniques for supercomputing, for dealing with big data problems, and for mining every possible piece of data from the surveys we have. The statistics, methods and codes we develop are cutting edge and can often be used in fields outside astronomy (for instance in finance, environmental science, business planning, and even tackling pandemics...)
Works
Search Professor Cullan Howlett’s works on UQ eSpace
2014
Journal Article
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: galaxy clustering measurements in the low-redshift sample of Data Release 11
Tojeiro, Rita, Ross, Ashley J., Burden, Angela, Samushia, Lado, Manera, Marc, Percival, Will J., Beutler, Florian, Brinkmann, J., Brownstein, Joel R., Cuesta, Antonio J., Dawson, Kyle, Eisenstein, Daniel J., Ho, Shirley, Howlett, Cullan, McBride, Cameron K., Montesano, Francisco, Olmstead, Matthew D., Parejko, John K., Reid, Beth, Sanchez, Ariel G., Schlegel, David J., Schneider, Donald P., Tinker, Jeremy L., Magana, Mariana Vargas and White, Martin (2014). The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: galaxy clustering measurements in the low-redshift sample of Data Release 11. Monthly Notices of the Royal Astronomical Society, 440 (3), 2222-2237. doi: 10.1093/mnras/stu371
2014
Conference Publication
Understanding cosmological measurements with a large number of mock galaxy catalogues
Manera, M., Percival, W. J., Ross, Ashley, Tojeiro, R., Samushia, L., Howlett, C., Vargas-Magaña, M., Burden, A. and SDSS-III BOSS Galaxy Working Group (2014). Understanding cosmological measurements with a large number of mock galaxy catalogues. 306th Symposium of The International-Astronomical-Union (IAU), Lisbon, Portugal, 25-29 May 2014. CAMBRIDGE: Cambridge University Press (CUP). doi: 10.1017/s1743921314013738
Funding
Current funding
Supervision
Availability
- Dr Cullan Howlett is:
- Not available for supervision
Supervision history
Current supervision
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Doctor Philosophy
Modelling exotic cosmological models in the era of next generation galaxy surveys
Principal Advisor
Other advisors: Professor Tamara Davis
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Doctor Philosophy
Using the motions of galaxies to probe fundamental physics
Principal Advisor
Other advisors: Professor Tamara Davis
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Doctor Philosophy
Investigating Gravitational Wave Cosmology with Simulated Data
Principal Advisor
Other advisors: Professor Tamara Davis
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Doctor Philosophy
Measuring Neutrino Mass with the Dark Energy Spectroscopic Instrument
Associate Advisor
Other advisors: Professor Tamara Davis
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Doctor Philosophy
Gravitational wave cosmology
Associate Advisor
Other advisors: Professor Tamara Davis
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Doctor Philosophy
Cosmology with the Dark Energy Survey
Associate Advisor
Other advisors: Professor Tamara Davis
Completed supervision
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2023
Doctor Philosophy
Whispers from the Big Bang-Cosmological Constraints from Galaxy Power Spectra
Principal Advisor
Other advisors: Professor Tamara Davis
Media
Enquiries
Contact Dr Cullan Howlett directly for media enquiries about:
- Astronomy
- Astrophysics
- Cosmology
- Dark energy
- Dark matter
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