
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
Featured
2023
Journal Article
Ho’oleilana: an individual baryon acoustic oscillation?
Tully, R. Brent, Howlett, Cullan and Pomarède, Daniel (2023). Ho’oleilana: an individual baryon acoustic oscillation?. Astrophysical Journal, 954 (2) 169, 1-14. doi: 10.3847/1538-4357/aceaf3
Featured
2023
Journal Article
Exploring binary black hole mergers and host galaxies with Shark and COMPAS
Rauf, Liana, Howlett, Cullan, Davis, Tamara M. and Lagos, Claudia D. P. (2023). Exploring binary black hole mergers and host galaxies with Shark and COMPAS. Monthly Notices of the Royal Astronomical Society, 523 (4), 5719-5737. doi: 10.1093/mnras/stad1757
Featured
2023
Journal Article
Using peculiar velocity surveys to constrain the growth rate of structure with the wide-angle effect
Lai, Yan, Howlett, Cullan and Davis, Tamara M. (2023). Using peculiar velocity surveys to constrain the growth rate of structure with the wide-angle effect. Monthly Notices of the Royal Astronomical Society, 518 (2), 1840-1858. doi: 10.1093/mnras/stac3252
Featured
2022
Journal Article
The Sloan Digital Sky Survey peculiar velocity catalogue
Howlett, Cullan, Said, Khaled, Lucey, John R., Colless, Matthew, Qin, Fei, Lai, Yan, Tully, R. Brent and Davis, Tamara M. (2022). The Sloan Digital Sky Survey peculiar velocity catalogue. Monthly Notices of the Royal Astronomical Society, 515 (1), 953-976. doi: 10.1093/mnras/stac1681
Featured
2021
Journal Article
Strengthening the bound on the mass of the lightest neutrino with terrestrial and cosmological experiments
Stöcker, Patrick, Balázs, Csaba, Bloor, Sanjay, Bringmann, Torsten, Gonzalo, Tomás E., Handley, Will, Hotinli, Selim, Howlett, Cullan, Kahlhoefer, Felix, Renk, Janina J., Scott, Pat, Vincent, Aaron C., White, Martin and The GAMBIT Cosmology Workgroup (2021). Strengthening the bound on the mass of the lightest neutrino with terrestrial and cosmological experiments. Physical Review D, 103 (12) 123508. doi: 10.1103/physrevd.103.123508
Featured
2020
Journal Article
Standard siren speeds: improving velocities in gravitational-wave measurements of H0
Howlett, Cullan and Davis, Tamara M. (2020). Standard siren speeds: improving velocities in gravitational-wave measurements of H0. Monthly Notices of the Royal Astronomical Society, 492 (3), 3803-3815. doi: 10.1093/mnras/staa049
Featured
2017
Journal Article
Measuring the growth rate of structure with type IA supernovae from LSST
Howlett, Cullan, Robotham, Aaron S. G., Lagos, Claudia D. P. and Kim, Alex G. (2017). Measuring the growth rate of structure with type IA supernovae from LSST. Astrophysical Journal, 847 (2) aa88c8, 128. doi: 10.3847/1538-4357/aa88c8
Featured
2017
Journal Article
Cosmological forecasts for combined and next-generation peculiar velocity surveys
Howlett, Cullan, Staveley-Smith, Lister and Blake, Chris (2017). Cosmological forecasts for combined and next-generation peculiar velocity surveys. Monthly Notices of the Royal Astronomical Society, 464 (3), 2517-2544. doi: 10.1093/mnras/stw2466
Featured
2015
Journal Article
L-PICOLA: a parallel code for fast dark matter simulation
Howlett, C., Manera, M. and Percival, W. J. (2015). L-PICOLA: a parallel code for fast dark matter simulation. Astronomy and Computing, 12, 109-126. doi: 10.1016/j.ascom.2015.07.003
Featured
2015
Journal Article
The clustering of the SDSS main galaxy sample - II. Mock galaxy catalogues and a measurement of the growth of structure from redshift space distortions at z=0.15
Howlett, Cullan, Ross, Ashley J., Samushia, Lado, Percival, Will J. and Manera, Marc (2015). The clustering of the SDSS main galaxy sample - II. Mock galaxy catalogues and a measurement of the growth of structure from redshift space distortions at z=0.15. Monthly Notices of the Royal Astronomical Society, 449 (1), 848-866. doi: 10.1093/mnras/stu2693
Featured
2015
Journal Article
The clustering of the SDSS DR7 main Galaxy sample - I. A 4 per cent distance measure at z=0.15
Ross, Ashley J., Samushia, Lado, Howlett, Cullan, Percival, Will J., Burden, Angela and Manera, Marc (2015). The clustering of the SDSS DR7 main Galaxy sample - I. A 4 per cent distance measure at z=0.15. Monthly Notices of the Royal Astronomical Society, 449 (1), 835-847. doi: 10.1093/mnras/stv154
Featured
2014
Journal Article
The clustering of galaxies in the SDSS-III baryon oscillation spectroscopic survey: Baryon acoustic oscillations in the data releases 10 and 11 galaxy samples
Anderson, Lauren, Aubourg, Élric, Bailey, Stephen, Beutler, Florian, Bhardwaj, Vaishali, Blanton, Michael, Bolton, Adam S., Brinkmann, J., Brownstein, Joel R., Burden, Angela, Chuang, Chia-Hsun, Cuesta, Antonio J., Dawson, Kyle S., Eisenstein, Daniel J., Escoffier, Stephanie, Gunn, James E., Guo, Hong, Ho, Shirley, Honscheid, Klaus, Howlett, Cullan, Kirkby, David, Lupton, Robert H., Manera, Marc, Maraston, Claudia, McBride, Cameron K., Mena, Olga, Montesano, Francesco, Nichol, Robert C., Nuza, Sebastián E. ... Zhao, Gong-Bo (2014). The clustering of galaxies in the SDSS-III baryon oscillation spectroscopic survey: Baryon acoustic oscillations in the data releases 10 and 11 galaxy samples. Monthly Notices of the Royal Astronomical Society, 441 (1), 24-62. doi: 10.1093/mnras/stu523
Featured
2012
Journal Article
CMB power spectrum parameter degeneracies in the era of precision cosmology
Howlett, Cullan, Lewis, Antony, Hall, Alex and Challinor, Anthony (2012). CMB power spectrum parameter degeneracies in the era of precision cosmology. Journal of Cosmology and Astroparticle Physics, 2012 (4) 027, 027-027. doi: 10.1088/1475-7516/2012/04/027
2025
Journal Article
Candidate strongly lensed type Ia supernovae in the Zwicky Transient Facility archive
Townsend, A., Nordin, J., Sagués Carracedo, A., Kowalski, M., Arendse, N., Dhawan, S., Goobar, A., Johansson, J., Mörtsell, E., Schulze, S., Andreoni, I., Fernández, E., Kim, A. G., Nugent, P. E., Prada, F., Rigault, M., Sarin, N., Sharma, D., Bellm, E. C., Coughlin, M. W., Dekany, R., Groom, S. L., Lacroix, L., Laher, R. R., Riddle, R., Aguilar, J., Ahlen, S., Bailey, S., Brooks, D. ... Zou, H. (2025). Candidate strongly lensed type Ia supernovae in the Zwicky Transient Facility archive. Astronomy and Astrophysics, 694 A146, A146. doi: 10.1051/0004-6361/202451082
2025
Journal Article
Improving the Determination of Supernova Cosmological Redshifts by Using Galaxy Groups
Peterson, Erik R., Carreres, Bastien, Carr, Anthony, Scolnic, Daniel, Bailey, Ava, Davis, Tamara M., Brout, Dillon, Howlett, Cullan, Jones, David O., Riess, Adam G., Said, Khaled and Taylor, Georgie (2025). Improving the Determination of Supernova Cosmological Redshifts by Using Galaxy Groups. The Astrophysical Journal, 980 (1) 21, 21. doi: 10.3847/1538-4357/ada285
2025
Journal Article
The hubble tension in our own backyard: DESI and the nearness of the coma cluster
Scolnic, Daniel, Riess, Adam G., Murakami, Yukei S., Peterson, Erik R., Brout, Dillon, Acevedo, Maria, Carreres, Bastien, Jones, David O., Said, Khaled, Howlett, Cullan and Anand, Gagandeep S. (2025). The hubble tension in our own backyard: DESI and the nearness of the coma cluster. The Astrophysical Journal Letters, 979 (1) L9. doi: 10.3847/2041-8213/ada0bd
2025
Journal Article
Suppressing the sample variance of DESI-like galaxy clustering with fast simulations
Ding, Z., Variu, A., Alam, S., Yu, Y., Chuang, C., Paillas, E., Garcia-Quintero, C., Chen, X., Mena-Fernández, J., Aguilar, J., Ahlen, S., Brooks, D., Claybaugh, T., de la Macorra, A., Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Gutierrez, G., Hahn, C., Honscheid, K., Howlett, C., Juneau, S., Kehoe, R., Kisner, T., Kremin, A., Lambert, A., Landriau, M. ... Zou, H. (2025). Suppressing the sample variance of DESI-like galaxy clustering with fast simulations. Journal of Cosmology and Astroparticle Physics, 2025 (01) 143, 143-1. doi: 10.1088/1475-7516/2025/01/143
2025
Journal Article
Forward modeling fluctuations in the DESI LRGs target sample using image simulations
Kong, H., Ross, A.J., Honscheid, K., Lang, D., Porredon, A., de Mattia, A., Rezaie, M., Zhou, R., Schlafly, E.F., Moustakas, J., Rosado-Marin, A., Aguilar, J., Ahlen, S., Brooks, D., Chaussidon, E., Claybaugh, T., Cole, S., de la Macorra, A., Dey, Arjun, Dey, Biprateep, Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Gutierrez, G., Howlett, C., Juneau, S., Kremin, A. ... Zou, H. (2025). Forward modeling fluctuations in the DESI LRGs target sample using image simulations. Journal of Cosmology and Astroparticle Physics, 2025 (01) 146, 146-1. doi: 10.1088/1475-7516/2025/01/146
2025
Journal Article
Blinding scheme for the scale-dependence bias signature of local primordial non-Gaussianity for DESI 2024
Chaussidon, E., de Mattia, A., Yèche, C., Aguilar, J., Ahlen, S., Brooks, D., Claybaugh, T., Cole, S., de la Macorra, A., Doel, P., Fanning, K., Gaztañaga, E., Gontcho, S.Gontcho A., Howlett, C., Kisner, T., Lambert, A., Le Guillou, L., Manera, M., Meisner, A., Miquel, R., Niz, G., Palanque-Delabrouille, N., Percival, W.J., Prada, F., Ross, A.J., Rossi, G., Sanchez, E., Schlegel, D., Schubnell, M. ... Zou, H. (2025). Blinding scheme for the scale-dependence bias signature of local primordial non-Gaussianity for DESI 2024. Journal of Cosmology and Astroparticle Physics, 2025 (01) 135, 135-1. doi: 10.1088/1475-7516/2025/01/135
2025
Journal Article
The construction of large-scale structure catalogs for the Dark Energy Spectroscopic Instrument
Ross, A.J., Aguilar, J., Ahlen, S., Alam, S., Anand, A., Bailey, S., Bianchi, D., Brieden, S., Brooks, D., Burtin, E., Carnero Rosell, A., Chaussidon, E., Claybaugh, T., Cole, S., Dawson, K., de la Macorra, A., de Mattia, A., Dey, A., Dey, B., Doel, P., Fanning, K., Ferraro, S., Ereza, J., Font-Ribera, A., Forero-Romero, J.E., Gaztañaga, E., Gil-Marín, H., Gontcho, S.Gontcho A., Gonzalez-Morales, A.X. ... Zou, H. (2025). The construction of large-scale structure catalogs for the Dark Energy Spectroscopic Instrument. Journal of Cosmology and Astroparticle Physics, 2025 (01) 125, 125-1. doi: 10.1088/1475-7516/2025/01/125
Funding
Current funding
Supervision
Availability
- Dr Cullan Howlett is:
- Not available for supervision
Supervision history
Current supervision
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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
Completing the Puzzle: Unveiling Clues for Gravitational Wave Astrophysics and Cosmology with Simulations
Principal Advisor
Other advisors: Professor Tamara Davis
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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
Completing the Puzzle: Unveiling Clues for Gravitational Wave Astrophysics and Cosmology with Simulations
Principal 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
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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
Completed supervision
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2025
Doctor Philosophy
Completing the Puzzle: Unveiling Clues for Gravitational Wave Astrophysics and Cosmology with Simulations
Principal Advisor
Other advisors: Professor Tamara Davis
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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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