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
2024
Journal Article
Faster cosmological analysis with power spectrum without simulations
Lai, Yan, Howlett, Cullan and Davis, Tamara M (2024). Faster cosmological analysis with power spectrum without simulations. Monthly Notices of the Royal Astronomical Society, 530 (4), 4519-4530. doi: 10.1093/mnras/stae1134
2024
Journal Article
Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument
DESI Collaboration, Adame, A. G., Aguilar, J., Ahlen, S., Alam, S., Aldering, G., Alexander, D. M., Alfarsy, R., Allende Prieto, C., Alvarez, M., Alves, O., Anand, A., Andrade-Oliveira, F., Armengaud, E., Asorey, J., Avila, S., Aviles, A., Bailey, S., Balaguera-Antolínez, A., Ballester, O., Baltay, C., Bault, A., Bautista, J., Behera, J., Beltran, S. F., BenZvi, S., Beraldo e Silva, L., Bermejo-Climent, J. R., Berti, A. ... Zu, Y. (2024). Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument. The Astronomical Journal, 167 (2) 62, 62. doi: 10.3847/1538-3881/ad0b08
2024
Journal Article
An effective description of Laniakea: impact on cosmology and the local determination of the Hubble constant
Giani, Leonardo, Howlett, Cullan, Said, Khaled, Davis, Tamara and Vagnozzi, Sunny (2024). An effective description of Laniakea: impact on cosmology and the local determination of the Hubble constant. Journal of Cosmology and Astroparticle Physics, 2024 (01) 071, 071. doi: 10.1088/1475-7516/2024/01/071
2023
Journal Article
Evaluating bulk flow estimators for CosmicFlows–4 measurements
Whitford, Abbé M., Howlett, Cullan and Davis, Tamara M. (2023). Evaluating bulk flow estimators for CosmicFlows–4 measurements. Monthly Notices of the Royal Astronomical Society, 526 (2), 3051-3071. doi: 10.1093/mnras/stad2764
2023
Journal Article
The galaxy number density profile of Halos
Qin, Fei, Parkinson, David, Stevens, Adam R. H. and Howlett, Cullan (2023). The galaxy number density profile of Halos. The Astrophysical Journal, 957 (1) 40, 1-11. doi: 10.3847/1538-4357/acfda5
2023
Journal Article
Can Einstein (rings) surf Gravitational Waves?
Giani, Leonardo, Howlett, Cullan and Davis, Tamara M. (2023). Can Einstein (rings) surf Gravitational Waves?. The Open Journal of Astrophysics, 6. doi: 10.21105/astro.2302.10472
2023
Journal Article
Target selection for the DESI peculiar velocity survey
Saulder, Christoph, Howlett, Cullan, Douglass, Kelly A, Said, Khaled, BenZvi, Segev, Ahlen, Steven, Aldering, Greg, Bailey, Stephen, Brooks, David, Davis, Tamara M, de la Macorra, Axel, Dey, Arjun, Font-Ribera, Andreu, Forero-Romero, Jaime E, Gontcho, Satya Gontcho A, Honscheid, Klaus, Kim, Alex G, Kisner, Theodore, Kremin, Anthony, Landriau, Martin, Levi, Michael E, Lucey, John, Meisner, Aaron M, Miquel, Ramon, Moustakas, John, Myers, Adam D, Palanque-Delabrouille, Nathalie, Percival, Will, Poppett, Claire ... Zou, Hu (2023). Target selection for the DESI peculiar velocity survey. Monthly Notices of the Royal Astronomical Society, 525 (1), 1106-1125. doi: 10.1093/mnras/stad2200
2023
Journal Article
Cross-correlating radial peculiar velocities and CMB lensing convergence
Giani, Leonardo, Howlett, Cullan, Ruggeri, Rossana, Bianchini, Federico, Said, Khaled and M. Davis, Tamara (2023). Cross-correlating radial peculiar velocities and CMB lensing convergence. Journal of Cosmology and Astroparticle Physics, 2023 (05) 002, 002. doi: 10.1088/1475-7516/2023/05/002
2023
Journal Article
WALLABY pre-pilot and pilot survey: the Tully Fisher relation in Eridanus, Hydra, Norma and NGC4636 fields
Courtois, Hélène M, Said, Khaled, Mould, Jeremy, Jarrett, T H, Pomarède, Daniel, Westmeier, Tobias, Staveley-Smith, Lister, Dupuy, Alexandra, Hong, Tao, Guinet, Daniel, Howlett, Cullan, Deg, Nathan, For, Bi-Qing, Kleiner, Dane, Koribalski, Bärbel, Lee-Waddell, Karen, Rhee, Jonghwan, Spekkens, Kristine, Wang, Jing, Wong, O I, Bigiel, Frank, Bosma, Albert, Colless, Matthew, Davis, Tamara, Holwerda, Benne, Karachentsev, Igor, Kraan-Korteweg, Renée C, McQuinn, Kristen B W, Meurer, Gerhardt ... Taylor, Edward (2023). WALLABY pre-pilot and pilot survey: the Tully Fisher relation in Eridanus, Hydra, Norma and NGC4636 fields. Monthly Notices of the Royal Astronomical Society, 519 (3), 4589-4607. doi: 10.1093/mnras/stac3246
2023
Journal Article
Cosmicflows-4
Tully, R. Brent, Kourkchi, Ehsan, Courtois, Hélène M., Anand, Gagandeep S., Blakeslee, John P., Brout, Dillon, Jaeger, Thomas de, Dupuy, Alexandra, Guinet, Daniel, Howlett, Cullan, Jensen, Joseph B., Pomarède, Daniel, Rizzi, Luca, Rubin, David, Said, Khaled, Scolnic, Daniel and Stahl, Benjamin E. (2023). Cosmicflows-4. The Astrophysical Journal, 944 (1) 94, 1-31. doi: 10.3847/1538-4357/ac94d8
2023
Journal Article
The DESI survey validation: results from visual inspection of bright galaxies, luminous red galaxies, and emission-line galaxies
Lan, Ting-Wen, Tojeiro, R., Armengaud, E., Prochaska, J. Xavier, Davis, T. M., Alexander, David M., Raichoor, A., Zhou, Rongpu, Yèche, Christophe, Balland, C., BenZvi, S., Berti, A., Canning, R., Carr, A., Chittenden, H., Cole, S., Cousinou, M.-C., Dawson, K., Dey, Biprateep, Douglass, K., Edge, A., Escoffier, S., Glanville, A., A Gontcho, S. Gontcho, Guy, J., Hahn, C., Howlett, C., Hwang, Ho Seong, Jiang, L. ... Zhou, Zhimin (2023). The DESI survey validation: results from visual inspection of bright galaxies, luminous red galaxies, and emission-line galaxies. The Astrophysical Journal, 943 (1) 68, 68. doi: 10.3847/1538-4357/aca5fa
2022
Journal Article
Full-shape galaxy power spectra and the curvature tension
Glanville, Aaron, Howlett, Cullan and Davis, Tamara (2022). Full-shape galaxy power spectra and the curvature tension. Monthly Notices of the Royal Astronomical Society, 517 (2), 3087-3100. doi: 10.1093/mnras/stac2891
2022
Journal Article
Overview of the instrumentation for the Dark Energy Spectroscopic Instrument
Abareshi, B., Aguilar, J., Ahlen, S., Alam, Shadab, Alexander, David M., Alfarsy, R., Allen, L., Prieto, C. Allende, Alves, O., Ameel, J., Armengaud, E., Asorey, J., Aviles, Alejandro, Bailey, S., Balaguera-Antolínez, A., Ballester, O., Baltay, C., Bault, A., Beltran, S. F., Benavides, B., BenZvi, S., Berti, A., Besuner, R., Beutler, Florian, Bianchi, D., Blake, C., Blanc, P., Blum, R., Bolton, A. ... Zu, Y. (2022). Overview of the instrumentation for the Dark Energy Spectroscopic Instrument. The Astronomical Journal, 164 (5) 207, 1-62. doi: 10.3847/1538-3881/ac882b
2022
Journal Article
H i HOD. I. The halo occupation distribution of H i Galaxies
Qin, Fei, Howlett, Cullan, Stevens, Adam R. H. and Parkinson, David (2022). H i HOD. I. The halo occupation distribution of H i Galaxies. The Astrophysical Journal, 937 (2) 113, 1-15. doi: 10.3847/1538-4357/ac8b6f
2022
Journal Article
Using peculiar velocity surveys to constrain neutrino masses
Whitford, Abbé M., Howlett, Cullan and Davis, Tamara M. (2022). Using peculiar velocity surveys to constrain neutrino masses. Monthly Notices of the Royal Astronomical Society, 513 (1), 345-362. doi: 10.1093/mnras/stac783
2022
Journal Article
WALLABY Pilot Survey: Public release of HI kinematic models for more than 100 galaxies from phase 1 of ASKAP pilot observations
Deg, N., Spekkens, K., Westmeier, T., Reynolds, T. N., Venkataraman, P., Goliath, S., Shen, A. X., Halloran, R., Bosma, A., Catinella, B, de Blok, W. J. G., Dénes, H., DiTeodoro, E. M., Elagali, A., For, B.-Q., Howlett, C, Józsa, G. I. G., Kamphuis, P., Kleiner, D., Koribalski, B, Lee-Waddell, K., Lelli, F., Lin, X., Murugeshan, C., Oh, S., Rhee, J., Scott, T. C., Staveley-Smith, L., van der Hulst, J. M. ... Wong, O. I. (2022). WALLABY Pilot Survey: Public release of HI kinematic models for more than 100 galaxies from phase 1 of ASKAP pilot observations. Publications of the Astronomical Society of Australia, 39 e059, 1-17. doi: 10.1017/pasa.2022.43
2022
Journal Article
WALLABY pilot survey: public release of H i data for almost 600 galaxies from phase 1 of ASKAP pilot observations
Westmeier, T., Deg, N., Spekkens, K., Reynolds, T. N., Shen, A. X., Gaudet, S., Goliath, S., Huynh, M. T., Venkataraman, P., Lin, X., O’Beirne, T., Catinella, B., Cortese, L., Dénes, H., Elagali, A., For, B.-Q., Józsa, G. I. G., Howlett, C., van der Hulst, J. M., Jurek, R. J., Kamphuis, P., Kilborn, V. A., Kleiner, D., Koribalski, B. S., Lee-Waddell, K., Murugeshan, C., Rhee, J., Serra, P., Shao, L. ... Said, K. (2022). WALLABY pilot survey: public release of H i data for almost 600 galaxies from phase 1 of ASKAP pilot observations. Publications of the Astronomical Society of Australia, 39 e058. doi: 10.1017/pasa.2022.50
2021
Journal Article
Cosmic flow measurement and mock sampling algorithm of Cosmicflows-4 Tully−Fisher catalog
Qin, Fei, Parkinson, David, Howlett, Cullan and Said, Khaled (2021). Cosmic flow measurement and mock sampling algorithm of Cosmicflows-4 Tully−Fisher catalog. The Astrophysical Journal, 922 (1) 59, 59. doi: 10.3847/1538-4357/ac249d
2021
Journal Article
The effect of systematic redshift biases in BAO cosmology
Glanville, Aaron, Howlett, Cullan and Davis, Tamara M. (2021). The effect of systematic redshift biases in BAO cosmology. Monthly Notices of the Royal Astronomical Society, 503 (3), 3510-3521. doi: 10.1093/mnras/stab657
2021
Journal Article
CosmoBit: A GAMBIT module for computing cosmological observables and likelihoods
Renk, Janina J., Stöcker, Patrick, Bloor, Sanjay, Hotinli, Selim, Balázs, Csaba, Bringmann, Torsten, Gonzalo, Tomás E., Handley, Will, Hoof, Sebastian, Howlett, Cullan, Kahlhoefer, Felix, Scott, Pat, Vincent, Aaron C. and White, Martin (2021). CosmoBit: A GAMBIT module for computing cosmological observables and likelihoods. Journal of Cosmology and Astroparticle Physics, 2021 (2) 022, 022-022. doi: 10.1088/1475-7516/2021/02/022
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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