Dr Cullan Howlett
Dr

Cullan Howlett

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0420776717

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

Astronomical instrumentation Astronomical sciences Cosmology and extragalactic astronomy Galactic astronomy General relativity and gravitational waves Physical Sciences

Qualifications

  • Doctor of Philosophy, University of Portsmouth

Research interests

  • 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.

  • 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.

  • 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.

  • 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...)

Search Professor Cullan Howlett’s works on UQ eSpace

87 works between 2012 and 2025
All (87) Journal Article (85) Conference Publication (2)

1 - 20 of 87 works

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

Ho’oleilana: an individual baryon acoustic oscillation?

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

Exploring binary black hole mergers and host galaxies with Shark and COMPAS

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

Using peculiar velocity surveys to constrain the growth rate of structure with the wide-angle effect

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

The Sloan Digital Sky Survey peculiar velocity catalogue

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

Strengthening the bound on the mass of the lightest neutrino with terrestrial and cosmological experiments

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

Standard siren speeds: improving velocities in gravitational-wave measurements of H0

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

Measuring the growth rate of structure with type IA supernovae from LSST

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

Cosmological forecasts for combined and next-generation peculiar velocity surveys

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

L-PICOLA: a parallel code for fast dark matter simulation

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

The clustering of the SDSS DR7 main Galaxy sample - I. A 4 per cent distance measure at z=0.15

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

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

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

The clustering of galaxies in the SDSS-III baryon oscillation spectroscopic survey: Baryon acoustic oscillations in the data releases 10 and 11 galaxy samples

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

CMB power spectrum parameter degeneracies in the era of precision cosmology

2025

Journal Article

DESIVAST: Catalogs of Low-redshift Voids Using Data from the DESI Data Release 1 Bright Galaxy Survey

Rincon, Hernan, Benzvi, Segev, Douglass, Kelly, Veyrat, Dahlia, Aguilar, Jessica Nicole, Ahlen, Steven, Bianchi, Davide, Brooks, David, Claybaugh, Todd, Cole, Shaun, de la Macorra, Axel, Doel, Peter, Font-Ribera, Andreu, Forero-Romero, Jaime E., Gaztañaga, Enrique, Gontcho A Gontcho, Satya, Gutierrez, Gaston, Honscheid, Klaus, Howlett, Cullan, Juneau, Stephanie, Kehoe, Robert, Koposov, Sergey, Lambert, Andrew, Landriau, Martin, Le Guillou, Laurent, Meisner, Aaron, Miquel, Ramon, Moustakas, John, Niz, Gustavo ... Zou, Hu (2025). DESIVAST: Catalogs of Low-redshift Voids Using Data from the DESI Data Release 1 Bright Galaxy Survey. The Astrophysical Journal, 982 (1) 38, 38-1. doi: 10.3847/1538-4357/adb559

DESIVAST: Catalogs of Low-redshift Voids Using Data from the DESI Data Release 1 Bright Galaxy Survey

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

Candidate strongly lensed type Ia supernovae in the Zwicky Transient Facility archive

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

Improving the Determination of Supernova Cosmological Redshifts by Using Galaxy Groups

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

The hubble tension in our own backyard: DESI and the nearness of the coma cluster

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

Mitigation of DESI fiber assignment incompleteness effect on two-point clustering with small angular scale truncated estimators

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

Validating the galaxy and quasar catalog-level blinding scheme for the DESI 2024 analysis

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

Semi-analytical covariance matrices for two-point correlation function for DESI 2024 data

Current funding

  • 2025 - 2028
    Cosmic Cartography to Counter Cosmic Conundrums
    ARC Discovery Projects
    Open grant
  • 2022 - 2025
    A Space Odyssey: Exploring the Universe with Gravitational-Wave Sirens
    ARC Discovery Projects
    Open grant

Availability

Dr Cullan Howlett is:
Not available for supervision

Supervision history

Current supervision

  • Doctor Philosophy

    Completing the Puzzle: Unveiling Clues for Gravitational Wave Astrophysics and Cosmology with Simulations

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Modelling exotic cosmological models in the era of next generation galaxy surveys

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Completing the Puzzle: Unveiling Clues for Gravitational Wave Astrophysics and Cosmology with Simulations

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Using the motions of galaxies to probe fundamental physics

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Investigating Gravitational Wave Cosmology with Simulated Data

    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

Enquiries

Contact Dr Cullan Howlett directly for media enquiries about:

  • Astronomy
  • Astrophysics
  • Cosmology
  • Dark energy
  • Dark matter

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