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
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
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
2025
Journal Article
A comparison between ShapeFit compression and Full-Modelling method with PyBird for DESI 2024 and beyond
Lai, Y., Howlett, C., Maus, M., Gil-Marín, H., Noriega, H.E., Ramírez-Solano, S., Zarrouk, P., Aguilar, J., Ahlen, S., Alves, O., Aviles, A., Brooks, D., Chen, S., Claybaugh, T., Davis, T.M., Dawson, K., de la Macorra, A., Doel, P., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Honscheid, K., Juneau, S., Landriau, M., Manera, M., Miquel, R., Mueller, E., Nadathur, S., Niz, G. ... Zou, H. (2025). A comparison between ShapeFit compression and Full-Modelling method with PyBird for DESI 2024 and beyond. Journal of Cosmology and Astroparticle Physics, 2025 (01) 139, 139-1. doi: 10.1088/1475-7516/2025/01/139
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
Optimal reconstruction of baryon acoustic oscillations for DESI 2024
Paillas, E., Ding, Z., Chen, X., Seo, H., Padmanabhan, N., de Mattia, A., Ross, A.J., Nadathur, S., Howlett, C., Aguilar, J., Ahlen, S., Alves, O., Andrade, U., Brooks, D., Buckley-Geer, E., Burtin, E., Chen, S., Claybaugh, T., Cole, S., Dawson, K., de la Macorra, A., Dey, Arjun, Doel, P., Fanning, K., Ferraro, S., Forero-Romero, J.E., Garcia-Quintero, C., Gaztañaga, E., Gil-Marín, H. ... Zou, H. (2025). Optimal reconstruction of baryon acoustic oscillations for DESI 2024. Journal of Cosmology and Astroparticle Physics, 2025 (01) 142, 142-1. doi: 10.1088/1475-7516/2025/01/142
2025
Journal Article
Validation of the DESI 2024 Lyα forest BAO analysis using synthetic datasets
Cuceu, Andrei, Herrera-Alcantar, Hiram K., Gordon, Calum, Martini, Paul, Guy, Julien, Font-Ribera, Andreu, Gonzalez-Morales, Alma X., Abdul Karim, M., Aguilar, J., Ahlen, S., Armengaud, E., Bault, A., Brooks, D., Claybaugh, T., de la Macorra, A., Doel, P., Fanning, K., Ferraro, S., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Gutierrez, G., Honscheid, K., Howlett, C., Karaçaylı, N.G., Kirkby, D., Kremin, A., Landriau, M., Le Goff, J.M. ... Zou, H. (2025). Validation of the DESI 2024 Lyα forest BAO analysis using synthetic datasets. Journal of Cosmology and Astroparticle Physics, 2025 (01), 148. doi: 10.1088/1475-7516/2025/01/148
2025
Journal Article
THE DESI-LENSING MOCK CHALLENGE: LARGE-SCALE COSMOLOGICAL ANALYSIS OF 3 × 2-PT STATISTICS
Blake, C., Garcia-Quintero, C., Ahlen, S., Bianchi, D., Brooks, D., Claybaugh, T., de la Macorra, A., Derose, J., Dey, A., Doel, P., Emas, N., Ferraro, S., Forero-Romero, J. E., Gutierrez, G., Heydenreich, S., Honscheid, K., Howlett, C., Ishak, M., Joudaki, S., Jullo, E., Kehoe, R., Kirkby, D., Kremin, A., Krolewski, A., Landriau, M., Lange, J. U., Leauthaud, A., Levi, M. E., Manera, M. ... Weaver, B. A. (2025). THE DESI-LENSING MOCK CHALLENGE: LARGE-SCALE COSMOLOGICAL ANALYSIS OF 3 × 2-PT STATISTICS. Open Journal of Astrophysics, 8. doi: 10.33232/001c.131903
2025
Journal Article
Production of alternate realizations of DESI fiber assignment for unbiased clustering measurement in data and simulations
Lasker, J., Carnero Rosell, A., Myers, A.D., Ross, A.J., Bianchi, D., Hanif, M.M.S., Kehoe, R., de Mattia, A., Napolitano, L., Percival, W.J., Staten, R., Aguilar, J., Ahlen, S., Bigwood, L., Brooks, D., Claybaugh, T., Cole, S., de la Macorra, A., Ding, Z., Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Gutierrez, G., Honscheid, K., Howlett, C., Juneau, S., Kremin, A. ... The DESI collaboration (2025). Production of alternate realizations of DESI fiber assignment for unbiased clustering measurement in data and simulations. Journal of Cosmology and Astroparticle Physics, 2025 (01) 127, 127. doi: 10.1088/1475-7516/2025/01/127
2025
Journal Article
Full Modeling and parameter compression methods in configuration space for DESI 2024 and beyond
Ramirez-Solano, S., Icaza-Lizaola, M., Noriega, H.E., Vargas-Magaña, M., Fromenteau, S., Aviles, A., Rodríguez-Martínez, F., Aguilar, J., Ahlen, S., Alves, O., Brieden, S., Brooks, D., Claybaugh, T., Cole, S., de la Macorra, A., Dey, Arjun, Dey, B., Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gil-Marín, H., Gontcho, S.Gontcho A., Honscheid, K., Howlett, C., Juneau, S., Lai, Y., Landriau, M., Manera, M. ... Zou, H. (2025). Full Modeling and parameter compression methods in configuration space for DESI 2024 and beyond. Journal of Cosmology and Astroparticle Physics, 2025 (01) 129, 129-1. doi: 10.1088/1475-7516/2025/01/129
2025
Journal Article
ELG spectroscopic systematics analysis of the DESI Data Release 1
Yu, J., Ross, A.J., Rocher, A., Alves, O., de Mattia, A., Forero-Sánchez, D., Kneib, J., Krolewski, A., Lan, T.-W., Rashkovetskyi, M., Aguilar, J., Ahlen, S., Bailey, S., Brooks, D., Chaussidon, E., Claybaugh, T., de la Macorra, A., Dey, Arjun, Dey, Biprateep, Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Honscheid, K., Howlett, C., Juneau, S., Kisner, T., Kremin, A. ... Zou, H. (2025). ELG spectroscopic systematics analysis of the DESI Data Release 1. Journal of Cosmology and Astroparticle Physics, 2025 (01) 126, 126. doi: 10.1088/1475-7516/2025/01/126
2025
Journal Article
Mitigation of DESI fiber assignment incompleteness effect on two-point clustering with small angular scale truncated estimators
Pinon, M., de Mattia, A., McDonald, P., Burtin, E., Ruhlmann-Kleider, V., White, M., Bianchi, D., Ross, A.J., Aguilar, J., Ahlen, S., Brooks, D., Cahn, R.N., Chaussidon, E., Claybaugh, T., Cole, S., de la Macorra, A., Dey, B., Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gontcho A Gontcho, S., Howlett, C., Kirkby, D., Kisner, T., Kremin, A., Lambert, A., Landriau, M., Lasker, J. ... Zou, H. (2025). Mitigation of DESI fiber assignment incompleteness effect on two-point clustering with small angular scale truncated estimators. Journal of Cosmology and Astroparticle Physics, 2025 (01), 131. doi: 10.1088/1475-7516/2025/01/131
2025
Journal Article
Validating the galaxy and quasar catalog-level blinding scheme for the DESI 2024 analysis
Andrade, U., Mena-Fernández, J., Awan, H., Ross, A.J., Brieden, S., Pan, J., de Mattia, A., Aguilar, J., Ahlen, S., Alves, O., Brooks, D., Buckley-Geer, E., Chaussidon, E., Claybaugh, T., Cole, S., de la Macorra, A., Dey, A., Doel, P., Fanning, K., Forero-Romero, J.E., Gaztañaga, E., Gil-Marín, H., Gontcho, S.Gontcho A., Guy, J., Hahn, C., Hanif, M.M.S., Honscheid, K., Howlett, C., Huterer, D. ... Weaver, B.A. (2025). Validating the galaxy and quasar catalog-level blinding scheme for the DESI 2024 analysis. Journal of Cosmology and Astroparticle Physics, 2025 (01), 128. doi: 10.1088/1475-7516/2025/01/128
2025
Journal Article
Semi-analytical covariance matrices for two-point correlation function for DESI 2024 data
Rashkovetskyi, M., Forero-Sánchez, D., de Mattia, A., Eisenstein, D.J., Padmanabhan, N., Seo, H., Ross, A.J., Aguilar, J., Ahlen, S., Alves, O., Andrade, U., Brooks, D., Burtin, E., Chen, X., Claybaugh, T., Cole, S., de la Macorra, A., Ding, Z., Doel, P., Fanning, K., Ferraro, S., Font-Ribera, A., Forero-Romero, J.E., Garcia-Quintero, C., Gil-Marín, H., Gontcho A Gontcho, S., Gonzalez-Morales, A.X., Gutierrez, G., Honscheid, K. ... Zou, H. (2025). Semi-analytical covariance matrices for two-point correlation function for DESI 2024 data. Journal of Cosmology and Astroparticle Physics, 2025 (01) 145, 145-1. doi: 10.1088/1475-7516/2025/01/145
2024
Journal Article
The redshift-space momentum power spectrum. III. Measuring the growth rate from the SDSSv survey using the auto- and cross-power spectrum of the galaxy density and momentum fields
Qin, Fei, Howlett, Cullan and Parkinson, David (2024). The redshift-space momentum power spectrum. III. Measuring the growth rate from the SDSSv survey using the auto- and cross-power spectrum of the galaxy density and momentum fields. The Astrophysical Journal, 978 (1) 7. doi: 10.3847/1538-4357/ad9391
2024
Journal Article
The Atacama Cosmology Telescope DR6 and DESI: structure formation over cosmic time with a measurement of the cross-correlation of CMB lensing and luminous red galaxies
Kim, Joshua, Sailer, Noah, Madhavacheril, Mathew S., Ferraro, Simone, Abril-Cabezas, Irene, Aguilar, Jessica Nicole, Ahlen, Steven, Richard Bond, J., Brooks, David, Burtin, Etienne, Calabrese, Erminia, Chen, Shi-Fan, Choi, Steve K., Claybaugh, Todd, Darwish, Omar, de la Macorra, Axel, DeRose, Joseph, Devlin, Mark, Dey, Arjun, Doel, Peter, Dunkley, Jo, Embil-Villagra, Carmen, Farren, Gerrit S., Font-Ribera, Andreu, Forero-Romero, Jaime E., Gaztañaga, Enrique, Gluscevic, Vera, Gontcho, Satya Gontcho A., Guy, Julien ... Zou, Hu (2024). The Atacama Cosmology Telescope DR6 and DESI: structure formation over cosmic time with a measurement of the cross-correlation of CMB lensing and luminous red galaxies. Journal of Cosmology and Astroparticle Physics, 2024 (12) 022, 1-47. doi: 10.1088/1475-7516/2024/12/022
2024
Journal Article
Analysis of DESI ×dES using the Lagrangian effective theory of LSS
Chen, S., Derose, J., Zhou, R., White, M., Ferraro, S., Blake, C., Lange, J. U., Wechsler, R. H., Aguilar, J., Ahlen, S., Brooks, D., Claybaugh, T., Dawson, K., De La Macorra, A., Doel, P., Font-Ribera, A., Gaztañaga, E., Gontcho A Gontcho, S., Gutierrez, G., Honscheid, K., Howlett, C., Kehoe, R., Kirkby, D., Kisner, T., Kremin, A., Landriau, M., Le Guillou, L., Manera, M., Meisner, A. ... Weaver, B. A. (2024). Analysis of DESI ×dES using the Lagrangian effective theory of LSS. Physical Review D, 110 (10) 103518. doi: 10.1103/PhysRevD.110.103518
2024
Journal Article
The MOST Hosts survey: spectroscopic observation of the host galaxies of ∼40,000 transients using DESI
Soumagnac, Maayane T., Nugent, Peter, Knop, Robert A., Ho, Anna Y. Q., Hohensee, William, Awbrey, Autumn, Andersen, Alexis, Aldering, Greg, Ventura, Matan, Aguilar, Jessica N., Ahlen, Steven, Benzvi, Segev Y., Brooks, David, Brout, Dillon, Claybaugh, Todd, Davis, Tamara M., Dawson, Kyle, de la Macorra, Axel, Dey, Arjun, Dey, Biprateep, Doel, Peter, Douglass, Kelly A., Forero-Romero, Jaime E., Gaztañaga, Enrique, Gontcho A Gontcho, Satya, Graur, Or, Guy, Julien, Hahn, ChangHoon, Honscheid, Klaus ... Zhou, Zhimin (2024). The MOST Hosts survey: spectroscopic observation of the host galaxies of ∼40,000 transients using DESI. The Astrophysical Journal Supplement Series, 275 (2) 22, 1-14. doi: 10.3847/1538-4365/ad76ae
2024
Journal Article
Value-added catalog of physical properties for more than 1.3 million galaxies from the DESI survey
Siudek, M., Pucha, R., Mezcua, M., Juneau, S., Aguilar, J., Ahlen, S., Brooks, D., Circosta, C., Claybaugh, T., Cole, S., Dawson, K., de la Macorra, A., Dey, A., Dey, B., Doel, P., Font-Ribera, A., Forero-Romero, J. E., Gaztañaga, E., Gontcho A Gontcho, S., Gutierrez, G., Honscheid, K., Howlett, C., Ishak, M., Kehoe, R., Kirkby, D., Kisner, T., Kremin, A., Lambert, A., Landriau, M. ... Zou, H. (2024). Value-added catalog of physical properties for more than 1.3 million galaxies from the DESI survey. Astronomy & Astrophysics, 691 A308, A308. doi: 10.1051/0004-6361/202451761
2024
Journal Article
Detection of the large-scale tidal field with galaxy multiplet alignment in the DESI Y1 spectroscopic survey
Lamman, Claire, Eisenstein, Daniel, Forero-Romero, Jaime E., Aguilar, Jessica Nicole, Ahlen, Steven, Bailey, Stephen, Bianchi, Davide, Brooks, David, Claybaugh, Todd, de la Macorra, Axel, Doel, Peter, Ferraro, Simone, Font-Ribera, Andreu, Gaztañaga, Enrique, Gontcho, Satya Gontcho A., Gutierrez, Gaston, Honscheid, Klaus, Howlett, Cullan, Kremin, Anthony, Lambert, Andrew, Landriau, Martin, Le Guillou, Laurent, Levi, Michael E., Meisner, Aaron, Miquel, Ramon, Moustakas, John, Newman, Jeffrey A., Niz, Gustavo, Prada, Francisco ... Zou, Hu (2024). Detection of the large-scale tidal field with galaxy multiplet alignment in the DESI Y1 spectroscopic survey. Monthly Notices of the Royal Astronomical Society, 534 (4), 3540-3551. doi: 10.1093/mnras/stae2290
2024
Journal Article
A trifecta of modelling tools: a Bayesian binary black hole model selection combining population synthesis and galaxy formation models
Rauf, Liana, Howlett, Cullan, Stevenson, Simon, Riley, Jeff and Willcox, Reinhold (2024). A trifecta of modelling tools: a Bayesian binary black hole model selection combining population synthesis and galaxy formation models. Monthly Notices of the Royal Astronomical Society, 534 (4), 3506-3539. doi: 10.1093/mnras/stae2288
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
Fundamental Plane distances from the Dark Energy Spectroscopic Instrument
Principal Advisor
Other advisors: Professor Tamara Davis
-
Doctor Philosophy
Measuring Neutrino Mass with the Dark Energy Spectroscopic Instrument
Associate Advisor
Other advisors: Professor Tamara Davis
-
Doctor Philosophy
Gravitational wave cosmology
Associate Advisor
Other advisors: Professor Tamara Davis
-
Doctor Philosophy
Cosmology with the Dark Energy Survey
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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