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

90 works between 2012 and 2025
All (90) Journal Article (88) Conference Publication (2)

41 - 60 of 90 works

2024

Journal Article

Baryon acoustic oscillation theory and modelling systematics for the DESI 2024 results

Chen, Shi-Fan, Howlett, Cullan, White, Martin, McDonald, Patrick, Ross, Ashley J, Seo, Hee-Jong, Padmanabhan, Nikhil, Aguilar, J, Ahlen, S, Alam, S, Alves, O, Andrade, U, Blum, R, Brooks, D, Chen, X, Cole, S, Dawson, K, de la Macorra, A, Dey, Arjun, Ding, Z, Doel, P, Ferraro, S, Font-Ribera, A, Forero-Sánchez, D, Forero-Romero, J E, Garcia-Quintero, C, Gaztañaga, E, Gontcho, S Gontcho A, Hanif, M M S ... Zhou, Z (2024). Baryon acoustic oscillation theory and modelling systematics for the DESI 2024 results. Monthly Notices of the Royal Astronomical Society, 534 (1), 544-574. doi: 10.1093/mnras/stae2090

Baryon acoustic oscillation theory and modelling systematics for the DESI 2024 results

2024

Journal Article

DESI 2024: reconstructing dark energy using crossing statistics with DESI DR1 BAO data

Calderon, R., Lodha, K., Shafieloo, A., Linder, E., Sohn, W., de Mattia, A., Cervantes-Cota, J.L., Crittenden, R., Davis, T.M., Ishak, M., Kim, A.G., Matthewson, W., Niz, G., Park, S., Aguilar, J., Ahlen, S., Allen, S., Brooks, D., Claybaugh, T., de la Macorra, A., Dey, A., Dey, B., Doel, P., Forero-Romero, J.E., Gaztañaga, E., Gontcho, S.Gontcho A., Honscheid, K., Howlett, C., Juneau, S. ... Zou, H. (2024). DESI 2024: reconstructing dark energy using crossing statistics with DESI DR1 BAO data. Journal of Cosmology and Astroparticle Physics, 2024 (10) 048, 048. doi: 10.1088/1475-7516/2024/10/048

DESI 2024: reconstructing dark energy using crossing statistics with DESI DR1 BAO data

2024

Journal Article

Catalog-level blinding on the bispectrum for DESI-like galaxy surveys

Novell-Masot, Sergi, Gil-Marin, Hector, Verde, Licia, Aguilar, J., Ahlen, S., Brieden, S., Brooks, D., Claybaugh, T., de la Macorra, A., Forero-Romero, J. E., Gaztañaga, E., Gontcho, S.Gontcho A., Gutierrez, G., Honscheid, K., Howlett, C., Kehoe, R., Kisner, T., Lambert, A., Levi, M. E., Manera, M., Meisner, A., Miquel, R., Niz, G., Prada, F., Rossi, G., Sanchez, E., Schubnell, M., Seo, H., Sprayberry, D. ... Weaver, B. A. (2024). Catalog-level blinding on the bispectrum for DESI-like galaxy surveys. Journal of Cosmology and Astroparticle Physics, 2024 (10) 089, 089. doi: 10.1088/1475-7516/2024/10/089

Catalog-level blinding on the bispectrum for DESI-like galaxy surveys

2024

Journal Article

Illuminating the dark side of the Universe using galaxy surveys

Howlett, Cullan (2024). Illuminating the dark side of the Universe using galaxy surveys. Australian Physics, 61 (4), 9-12.

Illuminating the dark side of the Universe using galaxy surveys

2024

Conference Publication

SIRMOS: NIR spectroscopy of 131,000,000 galaxies over 1 < z < 4 and R~1300

Content, Robert, Wang, Yun, Robberto, Massimo, Armus, Lee, Beutler, Florian, Bolzonella, Micol, Brieden, Samuel, Brinchmann, Jarle, Daddi, Emanuele, Dickinson, Mark, Faisst, Andreas, Hillenbrand, Lynne, Howlett, Cullan, Kartaltepe, Jeyhan, Koeppe, Dana, Lawrence, Jonathan S., Mei, Simona, Mueller, Eva-Maria, Nadathur, Seshadri, Ninkov, Zoran, Osato, Ken, Papovich, Casey, Percival, Will, Piotrowski, John, Pozzetti, Lucia, Raccanelli, Alvise, Rhodes, Jason D., Saito, Shun, Smee, Stephen A. ... Zemcov, Michael B. (2024). SIRMOS: NIR spectroscopy of 131,000,000 galaxies over 1 < z < 4 and R~1300. Conference on Space Telescopes and Instrumentation - Optical, Infrared, and Millimeter Wave, Yokohama, Japan, 16-22 June 2024. Bellingham, WA, United States: International Society for Optical Engineering. doi: 10.1117/12.3017865

SIRMOS: NIR spectroscopy of 131,000,000 galaxies over 1 < z < 4 and R~1300

2024

Journal Article

Archetype-based Redshift Estimation for the Dark Energy Spectroscopic Instrument Survey

Anand, Abhijeet, Guy, Julien, Bailey, Stephen, Moustakas, John, Aguilar, J., Ahlen, S., Bolton, A. S., Brodzeller, A., Brooks, D., Claybaugh, T., Cole, S., de la Macorra, A., Dey, Biprateep, Fanning, K., Forero-Romero, J. E., Gaztañaga, E., A Gontcho, S. Gontcho, Gutierrez, G., Honscheid, K., Howlett, C., Juneau, S., Kirkby, D., Kisner, T., Kremin, A., Lambert, A., Landriau, M., Le Guillou, L., Manera, M., Meisner, A. ... Zou, H. (2024). Archetype-based Redshift Estimation for the Dark Energy Spectroscopic Instrument Survey. The Astronomical Journal, 168 (3) 124, 124. doi: 10.3847/1538-3881/ad60c2

Archetype-based Redshift Estimation for the Dark Energy Spectroscopic Instrument Survey

2024

Journal Article

Galaxy and Mass Assembly (GAMA): stellar-to-dynamical mass relation. II. peculiar velocities

Dogruel, M. Burak, Taylor, Edward N., Cluver, Michelle, Colless, Matthew, de Graaff, Anna, Sonnenfeld, Alessandro, Lucey, John R., D’Eugenio, Francesco, Howlett, Cullan and Said, Khaled (2024). Galaxy and Mass Assembly (GAMA): stellar-to-dynamical mass relation. II. peculiar velocities. The Astrophysical Journal, 970 (2) 149. doi: 10.3847/1538-4357/ad4ce2

Galaxy and Mass Assembly (GAMA): stellar-to-dynamical mass relation. II. peculiar velocities

2024

Journal Article

The early data release of the dark energy spectroscopic instrument

DESI Collaboration, Adame, A. G., Aguilar, J., Ahlen, S., Alam, S., Aldering, G., Alexander, D. M., Alfarsy, R., Prieto, C. Allende, 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). The early data release of the dark energy spectroscopic instrument. The Astronomical Journal, 168 (2) 58. doi: 10.3847/1538-3881/ad3217

The early data release of the dark energy spectroscopic instrument

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

Faster cosmological analysis with power spectrum without simulations

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. doi: 10.3847/1538-3881/ad0b08

Validation of the scientific program for the Dark Energy Spectroscopic Instrument

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 (1) 071. doi: 10.1088/1475-7516/2024/01/071

An effective description of Laniakea: impact on cosmology and the local determination of the Hubble constant

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

Evaluating bulk flow estimators for CosmicFlows–4 measurements

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

The galaxy number density profile of Halos

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

Can Einstein (rings) surf Gravitational Waves?

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

Target selection for the DESI peculiar velocity survey

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

Cross-correlating radial peculiar velocities and CMB lensing convergence

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

WALLABY pre-pilot and pilot survey: the Tully Fisher relation in Eridanus, Hydra, Norma and NGC4636 fields

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

Cosmicflows-4

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

The DESI survey validation: results from visual inspection of bright galaxies, luminous red galaxies, and emission-line galaxies

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

Full-shape galaxy power spectra and the curvature tension

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

    Using the motions of galaxies to probe fundamental physics

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Fundamental Plane distances from the Dark Energy Spectroscopic Instrument

    Principal Advisor

    Other advisors: Professor Tamara Davis

  • Doctor Philosophy

    Cosmology with the Dark Energy Survey

    Associate 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

Completed supervision

Enquiries

Contact Dr Cullan Howlett directly for media enquiries about:

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

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