Skip to main content

Staff profile

Overview

Dr John Helly

Lead Software Developer

Affiliations
AffiliationTelephone
Lead Software Developer in the Department of Physics+44 (0) 191 33 43363
Chief Experimental Officer in the Institute for Computational Cosmology+44 (0) 191 33 43363

Publications

Journal Article

  • The FLAMINGO simulations data release
    Helly, J. C., McGibbon, R. J., Schaye, J., Schaller, M., McDonald, W., Braspenning, J., Broxterman, J. C., Costello, E. E., Elbers, W., Forouhar Moreno, V. J., Frenk, C. S., Jenkins, A., Kugel, R., McCarthy, I. G., Salcido, J., van Daalen, M. P., Vandenbroucke, B., & Yang, T. (2026). The FLAMINGO simulations data release. Astronomy and Computing, 57, Article 101159. https://doi.org/10.1016/j.ascom.2026.101159
  • FLAMINGO: tracing the co-evolution of hot gas and black holes in galaxy groups and clusters
    Costello, E. E., McCarthy, I. G., Salcido, J., Helly, J. C., McGibbon, R. J., Schaller, M., & Schaye, J. (2026). FLAMINGO: tracing the co-evolution of hot gas and black holes in galaxy groups and clusters. Monthly Notices of the Royal Astronomical Society, 549(4), Article stag945. https://doi.org/10.1093/mnras/stag945
  • COLIBRE: calibrating subgrid feedback in cosmological simulations that include a cold gas phase
    Chaikin, E., Schaye, J., Schaller, M., Ploeckinger, S., Bahé, Y. M., Benítez-Llambay, A., Correa, C., Forouhar Moreno, V. J., Frenk, C. S., Huško, F., Kugel, R., McGibbon, R., Richings, A. J., Trayford, J. W., Borrow, J., Crain, R. A., Helly, J. C., Lacey, C. G., Ludlow, A., & Nobels, F. S. J. (2026). COLIBRE: calibrating subgrid feedback in cosmological simulations that include a cold gas phase. Monthly Notices of the Royal Astronomical Society, 548(1), Article stag300. https://doi.org/10.1093/mnras/stag300
  • The COLIBRE project: cosmological hydrodynamical simulations of galaxy formation and evolution
    Schaye, J., Chaikin, E., Schaller, M., Ploeckinger, S., Huško, F., McGibbon, R. J., Trayford, J. W., Benítez-Llambay, A., Correa, C., Frenk, C. S., Richings, A. J., Forouhar Moreno, V. J., Bahé, Y. M., Borrow, J., Durrant, A., Gebek, A., Helly, J. C., Jenkins, A., Lacey, C. G., … Nobels, F. S. J. (2026). The COLIBRE project: cosmological hydrodynamical simulations of galaxy formation and evolution. Monthly Notices of the Royal Astronomical Society, 548(1), Article stag375. https://doi.org/10.1093/mnras/stag375
  • Ripples in the baryon to dark matter ratio in ΛCDM: implications for galaxy formation
    Jessop, O., Jenkins, A., Pontzen, A., Schaye, J., Schaller, M., & Helly, J. C. (2026). Ripples in the baryon to dark matter ratio in ΛCDM: implications for galaxy formation. Monthly Notices of the Royal Astronomical Society, 547(4), Article stag519. https://doi.org/10.1093/mnras/stag519
  • The resummation model in FLAMINGO: precisely predicting matter power suppression from observed halo baryon fractions
    van Daalen, M. P., Koutalios, I., Broxterman, J. C., Wolfs, B. J. H., Helly, J. C., Schaller, M., & Schaye, J. (2026). The resummation model in FLAMINGO: precisely predicting matter power suppression from observed halo baryon fractions. Monthly Notices of the Royal Astronomical Society, 545(2), Article staf2086. https://doi.org/10.1093/mnras/staf2086
  • Assessing subhalo finders in cosmological hydrodynamical simulations
    Forouhar Moreno, V. J., Helly, J., McGibbon, R., Schaye, J., Schaller, M., Han, J., Kugel, R., & Bahé, Y. M. (2025). Assessing subhalo finders in cosmological hydrodynamical simulations. Monthly Notices of the Royal Astronomical Society, 543(2), 1339-1372. https://doi.org/10.1093/mnras/staf1478
  • Constraints on the properties of νMSM dark matter using the satellite galaxies of the Milky Way
    Newton, O., Lovell, M. R., Frenk, C. S., Jenkins, A., Helly, J. C., Cole, S., Benson, A. J., & Hellwing, W. A. (2025). Constraints on the properties of νMSM dark matter using the satellite galaxies of the Milky Way. Monthly Notices of the Royal Astronomical Society, 541(4), 3713–3727. https://doi.org/10.1093/mnras/staf1223
  • The emperor’s new arc: gigaparsec patterns abound in a ΛCDM universe
    Sawala, T., Teeriaho, M., Frenk, C. S., Helly, J., Jenkins, A., Racz, G., Schaller, M., & Schaye, J. (2025). The emperor’s new arc: gigaparsec patterns abound in a ΛCDM universe. Monthly Notices of the Royal Astronomical Society: Letters, 541(1), L22-L27. https://doi.org/10.1093/mnrasl/slaf021
  • FLAMINGO: combining kinetic SZ effect and galaxy–galaxy lensing measurements to gauge the impact of feedback on large-scale structure
    McCarthy, I. G., Amon, A., Schaye, J., Schaan, E., Angulo, R. E., Salcido, J., Schaller, M., Bigwood, L., Elbers, W., Kugel, R., Helly, J. C., Forouhar Moreno, V. J., Frenk, C. S., McGibbon, R. J., Ondaro-Mallea, L., & van Daalen, M. P. (2025). FLAMINGO: combining kinetic SZ effect and galaxy–galaxy lensing measurements to gauge the impact of feedback on large-scale structure. Monthly Notices of the Royal Astronomical Society, 540(1), 143-163. https://doi.org/10.1093/mnras/staf731
  • The unabridged satellite luminosity function of Milky Way-like galaxies in ΛCDM: the contribution of ‘orphan’ satellites
    Santos-Santos, I. M. E., Frenk, C. S., Navarro, J. F., Cole, S., & Helly, J. (2025). The unabridged satellite luminosity function of Milky Way-like galaxies in ΛCDM: the contribution of ‘orphan’ satellites. Monthly Notices of the Royal Astronomical Society, 540(1), 1107-1123. https://doi.org/10.1093/mnras/staf749
  • On the accuracy of dark matter halo merger trees and the consequences for semi-analytic models of galaxy formation
    Chandro-Gómez, Á., Lagos, C. del P., Power, C., Moreno, V. J. F., Helly, J. C., Lacey, C. G., McGibbon, R. J., Schaller, M., & Schaye, J. (2025). On the accuracy of dark matter halo merger trees and the consequences for semi-analytic models of galaxy formation. Monthly Notices of the Royal Astronomical Society, 539(2), 776-807. https://doi.org/10.1093/mnras/staf519
  • The FLAMINGO project: the coupling between baryonic feedback and cosmology in light of the S8 tension
    Elbers, W., Frenk, C. S., Jenkins, A., Li, B., Helly, J. C., Kugel, R., Schaller, M., Schaye, J., Braspenning, J., Kwan, J., McCarthy, I. G., Salcido, J., van Daalen, M. P., Vandenbroucke, B., & Pascoli, S. (2025). The FLAMINGO project: the coupling between baryonic feedback and cosmology in light of the S8 tension. Monthly Notices of the Royal Astronomical Society, 537(2), 2160-2178. https://doi.org/10.1093/mnras/staf093
  • cosmICweb: Cosmological Initial Conditions for Zoom-in Simulations in the Cloud
    Buehlmann, M., Winkler, L., Hahn, O., Helly, J. C., & Jenkins, A. (2025). cosmICweb: Cosmological Initial Conditions for Zoom-in Simulations in the Cloud. The Open Journal of Astrophysics, 8. https://doi.org/10.33232/001c.133696
  • Cosmological feedback from a halo assembly perspective
    Lucie-Smith, L., Peiris, H. V., Pontzen, A., Halder, A., Schaye, J., Schaller, M., Helly, J., McGibbon, R. J., & Elbers, W. (2025). Cosmological feedback from a halo assembly perspective. Physical Review D, 112(6), Article 063541. https://doi.org/10.1103/vh8n-9cr2
  • A unified model for the clustering of quasars and galaxies at z ≈ 6
    Pizzati, E., Hennawi, J. F., Schaye, J., Schaller, M., Eilers, A., Wang, F., Frenk, C. S., Elbers, W., Helly, J. C., Mackenzie, R., Matthee, J., Bordoloi, R., Kashino, D., Naidu, R. P., & Yue, M. (2024). A unified model for the clustering of quasars and galaxies at z ≈ 6. Monthly Notices of the Royal Astronomical Society, 534(4), 3155-3175. https://doi.org/10.1093/mnras/stae2307
  • The FLAMINGO project: a comparison of galaxy cluster samples selected on mass, X-ray luminosity, Compton-Y parameter, or galaxy richness
    Kugel, R., Schaye, J., Schaller, M., McCarthy, I. G., Braspenning, J., Helly, J. C., Forouhar Moreno, V. J., & McGibbon, R. J. (2024). The FLAMINGO project: a comparison of galaxy cluster samples selected on mass, X-ray luminosity, Compton-Y parameter, or galaxy richness. Monthly Notices of the Royal Astronomical Society, 534(3), 2378-2396. https://doi.org/10.1093/mnras/stae2218
  • EIGER. VI. The Correlation Function, Host Halo Mass, and Duty Cycle of Luminous Quasars at z ≳ 6
    Eilers, A., Mackenzie, R., Pizzati, E., Matthee, J., Hennawi, J. F., Zhang, H., Bordoloi, R., Kashino, D., Lilly, S. J., Naidu, R. P., Simcoe, R. A., Yue, M., Frenk, C. S., Helly, J. C., Schaller, M., & Schaye, J. (2024). EIGER. VI. The Correlation Function, Host Halo Mass, and Duty Cycle of Luminous Quasars at z ≳ 6. The Astrophysical Journal, 974(2), Article 275. https://doi.org/10.3847/1538-4357/ad778b
  • Relativistic SZ temperatures and hydrostatic mass bias for massive clusters in the FLAMINGO simulations
    Kay, S. T., Braspenning, J., Chluba, J., Helly, J. C., Kugel, R., Schaller, M., & Schaye, J. (2024). Relativistic SZ temperatures and hydrostatic mass bias for massive clusters in the FLAMINGO simulations. Monthly Notices of the Royal Astronomical Society, 534(1), 251-270. https://doi.org/10.1093/mnras/stae1991
  • The FLAMINGO project: galaxy clusters in comparison to X-ray observations
    Braspenning, J., Schaye, J., Schaller, M., McCarthy, I. G., Kay, S. T., Helly, J. C., Kugel, R., Elbers, W., Frenk, C. S., Kwan, J., Salcido, J., van Daalen, M. P., & Vandenbroucke, B. (2024). The FLAMINGO project: galaxy clusters in comparison to X-ray observations. Monthly Notices of the Royal Astronomical Society, 533(3), 2656-2676. https://doi.org/10.1093/mnras/stae1436
  • Swift: A modern highly-parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications
    Schaller, M., Borrow, J., Draper, P. W., Ivkovic, M., McAlpine, S., Vandenbroucke, B., Bahé, Y., Chaikin, E., Chalk, A. B. G., Chan, T. K., Correa, C., van Daalen, M., Elbers, W., Gonnet, P., Hausammann, L., Helly, J., Huško, F., Kegerreis, J. A., Nobels, F. S. J., … Xiang, Z. (2024). Swift: A modern highly-parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications. Monthly Notices of the Royal Astronomical Society, 530(2), 2378–2419. https://doi.org/10.1093/mnras/stae922
  • The FLAMINGO project: baryonic impact on weak gravitational lensing convergence peak counts
    Broxterman, J. C., Schaller, M., Schaye, J., Hoekstra, H., Kuijken, K., Helly, J. C., Kugel, R., Braspenning, J., Elbers, W., Frenk, C. S., Kwan, J., McCarthy, I. G., Salcido, J., van Daalen, M. P., & Vandenbroucke, B. (2024). The FLAMINGO project: baryonic impact on weak gravitational lensing convergence peak counts. Monthly Notices of the Royal Astronomical Society, 529(3), 2309-2326. https://doi.org/10.1093/mnras/stae698
  • Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations versus fast approximations
    Upadhye, A., Kwan, J., McCarthy, I. G., Salcido, J., Helly, J. C., Kugel, R., Schaller, M., Schaye, J., Braspenning, J., Elbers, W., Frenk, C. S., van Daalen, M. P., Vandenbroucke, B., & Broxterman, J. C. (2024). Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations versus fast approximations. Monthly Notices of the Royal Astronomical Society, 529(2), 1862-1876. https://doi.org/10.1093/mnras/stae663
  • The FLAMINGO project: revisiting the S8 tension and the role of baryonic physics
    Elbers, W., Helly, J., Frenk, C., McCarthy, I. G., Salcido, J., Schaye, J., Kwan, J., Schaller, M., Braspenning, J., van Daalen, M. P., Vandenbroucke, B., Conley, J. T., Font, A. S., & Upadhye, A. (2023). The FLAMINGO project: revisiting the S8 tension and the role of baryonic physics. Monthly Notices of the Royal Astronomical Society, 526(4), 5494–5519. https://doi.org/10.1093/mnras/stad3107
  • The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys
    Schaye, J., Kugel, R., Schaller, M., Helly, J. C., Braspenning, J., Elbers, W., McCarthy, I. G., van Daalen, M. P., Vandenbroucke, B., Frenk, C. S., Kwan, J., Salcido, J., Bahe´, Y. M., Borrow, J., Chaikin, E., Hahn, O., Husko, F., Jenkins, A., Lacey, C. G., & Nobels, F. S. J. (2023). The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys. Monthly Notices of the Royal Astronomical Society, 526(4), 4978–5020. https://doi.org/10.1093/mnras/stad2419
  • Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations
    Wang, W., Zhu, L., Li, Z., Chen, Y., Han, J., He, F., Yang, X., Jing, Y., Frenk, C., Nie, J., Tian, H., Liu, C., Cao, Y., Qiu, X., Helly, J., Grand, R. J. J., & Gomez, F. A. (2022). Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations. The Astrophysical Journal, 941(2), Article 108. https://doi.org/10.3847/1538-4357/ac9b19
  • SIBELIUS-DARK: a galaxy catalogue of the local volume from a constrained realization simulation
    McAlpine, S., Helly, J. C., Schaller, M., Sawala, T., Lavaux, G., Jasche, J., Frenk, C. S., Jenkins, A., Lucey, J. R., & Johansson, P. H. (2022). SIBELIUS-DARK: a galaxy catalogue of the local volume from a constrained realization simulation. Monthly Notices of the Royal Astronomical Society, 512(4), 5823-5847. https://doi.org/10.1093/mnras/stac295
  • Halo merger tree comparison: impact on galaxy formation models
    Gómez, J. S., Padilla, N., Helly, J., Lacey, C., Baugh, C., & Lagos, C. (2022). Halo merger tree comparison: impact on galaxy formation models. Monthly Notices of the Royal Astronomical Society, 510(4), 5500-5519. https://doi.org/10.1093/mnras/stab3661
  • The DESI N-body simulation project – I. Testing the robustness of simulations for the DESI dark time survey
    Grove, C., Chuang, C., Devi, N. C., Garrison, L., L’Huillier, B., Feng, Y., Helly, J., Hernández-Aguayo, C., Alam, S., Zhang, H., Yu, Y., Cole, S., Eisenstein, D., Norberg, P., Wechsler, R., Brooks, D., Dawson, K., Landriau, M., Meisner, A., … Valenzuela, O. (2022). The DESI N-body simulation project – I. Testing the robustness of simulations for the DESI dark time survey. Monthly Notices of the Royal Astronomical Society, 515(2). https://doi.org/10.1093/mnras/stac1947
  • Observing the Stellar Halo of Andromeda in Cosmological Simulations: The AURIGA2PANDAS Pipeline
    Thomas, G. F., Martin, N. F., Fattahi, A., Ibata, R. A., Helly, J., McConnachie, A. W., Frenk, C., Gómez, F. A., Grand, R. J., Gwyn, S., Mackey, D., Marinacci, F., & Pakmor, R. (2021). Observing the Stellar Halo of Andromeda in Cosmological Simulations: The AURIGA2PANDAS Pipeline. Astrophysical Journal, 910(2), Article 92. https://doi.org/10.3847/1538-4357/abdfd2
  • Constraints on the properties of warm dark matter using the satellite galaxies of the Milky Way
    Newton, O., Leo, M., Cautun, M., Jenkins, A., Frenk, C. S., Lovell, M. R., Helly, J. C., Benson, A. J., & Cole, S. (2021). Constraints on the properties of warm dark matter using the satellite galaxies of the Milky Way. Journal of Cosmology and Astroparticle Physics, 2021(08), Article 062. https://doi.org/10.1088/1475-7516/2021/08/062
  • Do model emission line galaxies live in filaments at z∼1?
    Gonzalez-Perez, V., Cui, W., Contreras, S., Baugh, C., Comparat, J., Griffin, A., Helly, J., Knebe, A., Lacey, C., & Norberg, P. (2020). Do model emission line galaxies live in filaments at z∼1? Monthly Notices of the Royal Astronomical Society, 498(2), 1852-1870. https://doi.org/10.1093/mnras/staa2504
  • The total satellite population of the Milky Way
    Newton, O., Cautun, M., Jenkins, A., Frenk, C. S., & Helly, J. C. (2018). The total satellite population of the Milky Way. Monthly Notices of the Royal Astronomical Society, 479(3), 2853-2870. https://doi.org/10.1093/mnras/sty1085
  • Comparing galaxy formation in semi-analytic models and hydrodynamical simulations
    Mitchell, P. D., Lacey, C. G., Lagos, C. D., Frenk, C. S., Bower, R. G., Cole, S., Helly, J. C., Schaller, M., Gonzalez-Perez, V., & Theuns, T. (2018). Comparing galaxy formation in semi-analytic models and hydrodynamical simulations. Monthly Notices of the Royal Astronomical Society, 474(1), 492-521. https://doi.org/10.1093/mnras/stx2770
  • Baryon effects on void statistics in the EAGLE simulation
    Paillas, E., Lagos, C. D., Padilla, N., Tissera, P., Helly, J., & Schaller, M. (2017). Baryon effects on void statistics in the EAGLE simulation. Monthly Notices of the Royal Astronomical Society, 470(4), 4434-4452. https://doi.org/10.1093/mnras/stx1514
  • A chronicle of galaxy mass assembly in the EAGLE simulation
    Qu, Y., Helly, J., Bower, R., Theuns, T., Crain, R., Frenk, C., Furlong, M., McAlpine, S., Schaller, M., Schaye, J., & White, S. (2017). A chronicle of galaxy mass assembly in the EAGLE simulation. Monthly Notices of the Royal Astronomical Society, 464(2), 1659-1675. https://doi.org/10.1093/mnras/stw2437
  • A unified multiwavelength model of galaxy formation
    Lacey, C. G., Baugh, C. M., Frenk, C. S., Benson, A. J., Bower, R. G., Cole, S., Gonzalez-Perez, V., Helly, J. C., Lagos, C. D., & Mitchell, P. D. (2016). A unified multiwavelength model of galaxy formation. Monthly Notices of the Royal Astronomical Society, 462(4), 3854-3911. https://doi.org/10.1093/mnras/stw1888
  • Galaxies in the EAGLE hydrodynamical simulation and in the Durham and Munich semi-analytical models
    Guo, Q., Gonzalez-Perez, V., Guo, Q., Schaller, M., Furlong, M., Bower, R., Cole, S., Crain, R., Frenk, C., Helly, J., Lacey, C., Lagos, C. d. P., Mitchell, P., Schaye, J., & Theuns, T. (2016). Galaxies in the EAGLE hydrodynamical simulation and in the Durham and Munich semi-analytical models. Monthly Notices of the Royal Astronomical Society, 461(4), 3457-3482. https://doi.org/10.1093/mnras/stw1525
  • The Copernicus Complexio: a high-resolution view of the small-scale Universe
    Hellwing, W., Frenk, C., Cautun, M., Bose, S., Helly, J., Jenkins, A., Sawala, T., & Cytowski, M. (2016). The Copernicus Complexio: a high-resolution view of the small-scale Universe. Monthly Notices of the Royal Astronomical Society, 457(4), 3492-3509. https://doi.org/10.1093/mnras/stw214
  • A new methodology to test galaxy formation models using the dependence of clustering on stellar mass
    Campbell, D., Baugh, C., Mitchell, P., Helly, J., Gonzalez-Perez, V., Lacey, C., Lagos, C. d. P., Simha, V., & Farrow, D. (2015). A new methodology to test galaxy formation models using the dependence of clustering on stellar mass. Monthly Notices of the Royal Astronomical Society, 452(1), 852-871. https://doi.org/10.1093/mnras/stv1315
  • N-body dark matter haloes with simple hierarchical histories
    Jiang, L., Helly, J., Cole, S., & Frenk, C. (2014). N-body dark matter haloes with simple hierarchical histories. Monthly Notices of the Royal Astronomical Society, 440(3), 2115-2135. https://doi.org/10.1093/mnras/stu390
  • Simulations of the formation, evolution and clustering of galaxies and quasars
    Springel, V., White, S., Jenkins, A., Frenk, C., Yoshida, N., Gao, L., Navarro, J., Thacker, R., Croton, D., Helly, J., Peacock, J., Cole, S., Thomas, P., Couchman, H., Evrard, A., Colberg, J., & Pearce, F. (2005). Simulations of the formation, evolution and clustering of galaxies and quasars. Nature, 435(7042), 629-636. https://doi.org/10.1038/nature03597
  • A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation
    Helly, J., Cole, S., Frenk, C., Baugh, C., Benson, A., Lacey, C., & Pearce, F. (2003). A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation. Monthly Notices of the Royal Astronomical Society, 338(4), 913-925. https://doi.org/10.1046/j.1365-8711.2003.06152.x
  • Galaxy formation using halo merger histories taken from N-body simulations
    Helly, J., Cole, S., Frenk, C., Baugh, C., Benson, A., & Lacey, C. (2003). Galaxy formation using halo merger histories taken from N-body simulations. Monthly Notices of the Royal Astronomical Society, 338(4), 903-912. https://doi.org/10.1046/j.1365-8711.2003.06151.x