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Dr John Helly's Outputs (28)

EIGER. VI. The Correlation Function, Host Halo Mass, and Duty Cycle of Luminous Quasars at z ≳ 6 (2024)
Journal Article
Eilers, A.-C., 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

We expect luminous (M 1450 ≲ −26.5) high-redshift quasars to trace the highest-density peaks in the early Universe. Here, we present observations of four z ≳ 6 quasar fields using JWST/NIRCam in the imaging and wide-field slitless spectroscopy mode a... Read More about EIGER. VI. The Correlation Function, Host Halo Mass, and Duty Cycle of Luminous Quasars at z ≳ 6.

Swift: A modern highly-parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications (2024)
Journal Article
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., Ploeckinger, S., …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

Numerical simulations have become one of the key tools used by theorists in all the fields of astrophysics and cosmology. The development of modern tools that target the largest existing computing systems and exploit state-of-the-art numerical method... Read More about Swift: A modern highly-parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications.

Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations versus fast approximations (2024)
Journal Article
Upadhye, A., Kwan, J., McCarthy, I. G., Salcido, J., Helly, J. C., Kugel, R., …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

Weak lensing of the cosmic microwave background is rapidly emerging as a powerful probe of neutrinos, dark energy, and new
physics. We present a fast computation of the non-linear CMB lensing power spectrum that combines non-linear perturbation
the... Read More about Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations versus fast approximations.

The FLAMINGO project: baryonic impact on weak gravitational lensing convergence peak counts (2024)
Journal Article
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

Weak gravitational lensing convergence peaks, the local maxima in weak lensing convergence maps, have been shown to contain valuable cosmological information complementary to commonly used two-point statistics. To exploit the full power of weak lensi... Read More about The FLAMINGO project: baryonic impact on weak gravitational lensing convergence peak counts.

The FLAMINGO project: revisiting the S8 tension and the role of baryonic physics (2023)
Journal Article
Elbers, W., Helly, J., Frenk, C., McCarthy, I. G., Salcido, J., Schaye, J., …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

A number of recent studies have found evidence for a tension between observations of large-scale structure (LSS) and the predictions of the standard model of cosmology with the cosmological parameters fit to the cosmic microwave background (CMB). The... Read More about The FLAMINGO project: revisiting the S8 tension and the role of baryonic physics.

The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys (2023)
Journal Article
Schaye, J., Kugel, R., Schaller, M., Helly, . J. C., Braspenning, J., Elbers, W., …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

We introduce the Virgo Consortium’s FLAMINGO suite of hydrodynamical simulations for cosmology and galaxy cluster physics. To ensure the simulations are sufficiently realistic for studies of large-scale structure, the subgrid prescriptions for stella... Read More about The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys.

The Milky Way’s plane of satellites is consistent with ΛCDM (2022)
Journal Article
Sawala, T., Cautun, M., Frenk, C., Helly, J., Jasche, J., Jenkins, A., …Schaller, M. (2023). The Milky Way’s plane of satellites is consistent with ΛCDM. Nature Astronomy, 7(4), 481-491. https://doi.org/10.1038/s41550-022-01856-z

The Milky Way is surrounded by 11 ‘classical’ satellite galaxies in a remarkable configuration: a thin plane that is possibly rotationally supported. Such a structure is thought to be highly unlikely to arise in the standard (ΛCDM) cosmological model... Read More about The Milky Way’s plane of satellites is consistent with ΛCDM.

Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations (2022)
Journal Article
Wang, W., Zhu, L., Li, Z., Chen, Y., Han, J., He, F., …Gomez, F. A. (2022). Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations. Astrophysical Journal, 941(2), Article 108. https://doi.org/10.3847/1538-4357/ac9b19

Mock member stars for 28 dwarf galaxies are constructed from the cosmological auriga simulation, which reflects the dynamical status of realistic stellar tracers. Axisymmetric Jeans Anisotropic Multi-Gaussian Expansion (jam) modeling is applied to 60... Read More about Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations.

The DESI N-body simulation project – I. Testing the robustness of simulations for the DESI dark time survey (2022)
Journal Article
Grove, C., Chuang, C., Devi, N. C., Garrison, L., L’Huillier, B., Feng, Y., …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

Analysis of large galaxy surveys requires confidence in the robustness of numerical simulation methods. The simulations are used to construct mock galaxy catalogues to validate data analysis pipelines and identify potential systematics. We compare th... Read More about The DESI N-body simulation project – I. Testing the robustness of simulations for the DESI dark time survey.

SIBELIUS-DARK: a galaxy catalogue of the local volume from a constrained realization simulation (2022)
Journal Article
McAlpine, S., Helly, J. C., Schaller, M., Sawala, T., Lavaux, G., Jasche, J., …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

We present SIBELIUS-DARK, a constrained realization simulation of the local volume to a distance of 200 Mpc from the Milky Way. SIBELIUS-DARK is the first study of the ‘Simulations Beyond The Local Universe’ (SIBELIUS) project, which has the goal of... Read More about SIBELIUS-DARK: a galaxy catalogue of the local volume from a constrained realization simulation.

Halo merger tree comparison: impact on galaxy formation models (2021)
Journal Article
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

We examine the effect of using different halo finders and merger tree building algorithms on galaxy properties predicted using the GALFORM semi-analytical model run on a high resolution, large volume dark matter simulation. The halo finders/tree buil... Read More about Halo merger tree comparison: impact on galaxy formation models.

Constraints on the properties of warm dark matter using the satellite galaxies of the Milky Way (2021)
Journal Article
Newton, O., Leo, M., Cautun, M., Jenkins, A., Frenk, C. S., Lovell, M. R., …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

The satellite galaxies of the Milky Way (MW) are effective probes of the underlying dark matter (DM) substructure, which is sensitive to the nature of the DM particle. In particular, a class of DM models have a power spectrum cut-off on the mass scal... Read More about Constraints on the properties of warm dark matter using the satellite galaxies of the Milky Way.

Observing the Stellar Halo of Andromeda in Cosmological Simulations: The AURIGA2PANDAS Pipeline (2021)
Journal Article
Thomas, G. F., Martin, N. F., Fattahi, A., Ibata, R. A., Helly, J., McConnachie, A. W., …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

We present a direct comparison of the Pan-Andromeda Archaeological Survey (PAndAS) observations of the stellar halo of M31 with the stellar halos of six galaxies from the Auriga simulations. We process the simulated halos through the Auriga2PAndAS pi... Read More about Observing the Stellar Halo of Andromeda in Cosmological Simulations: The AURIGA2PANDAS Pipeline.

Do model emission line galaxies live in filaments at z∼1? (2020)
Journal Article
Gonzalez-Perez, V., Cui, W., Contreras, S., Baugh, C., Comparat, J., Griffin, A., …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

Current and future cosmological surveys are targeting star-forming galaxies at z∼ 1 with nebular emission lines. We use a state-of-the-art semi-analytical model of galaxy formation and evolution to explore the large scale environment of star-forming... Read More about Do model emission line galaxies live in filaments at z∼1?.

The total satellite population of the Milky Way (2018)
Journal Article
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

The total number and luminosity function of the population of dwarf galaxies of the Milky Way (MW) provide important constraints on the nature of the dark matter and on the astrophysics of galaxy formation at low masses. However, only a partial censu... Read More about The total satellite population of the Milky Way.

Comparing galaxy formation in semi-analytic models and hydrodynamical simulations (2017)
Journal Article
Mitchell, P. D., Lacey, C. G., Lagos, C. D., Frenk, C. S., Bower, R. G., Cole, S., …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

It is now possible for hydrodynamical simulations to reproduce a representative galaxy population. Accordingly, it is timely to assess critically some of the assumptions of traditional semi-analytic galaxy formation models. We use the EAGLE simulatio... Read More about Comparing galaxy formation in semi-analytic models and hydrodynamical simulations.

Baryon effects on void statistics in the EAGLE simulation (2017)
Journal Article
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

Cosmic voids are promising tools for cosmological tests due to their sensitivity to dark energy, modified gravity and alternative cosmological scenarios. Most previous studies in the literature of void properties use cosmological N-body simulations o... Read More about Baryon effects on void statistics in the EAGLE simulation.

A chronicle of galaxy mass assembly in the EAGLE simulation (2016)
Journal Article
Qu, Y., Helly, J., Bower, R., Theuns, T., Crain, R., Frenk, C., …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

We analyse the mass assembly of central galaxies in the Evolution and Assembly of Galaxies and their Environments (EAGLE) hydrodynamical simulations. We build merger trees to connect galaxies to their progenitors at different redshifts and characteri... Read More about A chronicle of galaxy mass assembly in the EAGLE simulation.

A unified multiwavelength model of galaxy formation (2016)
Journal Article
Lacey, C. G., Baugh, C. M., Frenk, C. S., Benson, A. J., Bower, R. G., Cole, S., …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

We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formatio... Read More about A unified multiwavelength model of galaxy formation.

Galaxies in the EAGLE hydrodynamical simulation and in the Durham and Munich semi-analytical models (2016)
Journal Article
Guo, Q., Gonzalez-Perez, V., Guo, Q., Schaller, M., Furlong, M., Bower, R., …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

We compare global predictions from the EAGLE hydrodynamical simulation, and two semi-analytic (SA) models of galaxy formation, L-GALAXIES and GALFORM. All three models include the key physical processes for the formation and evolution of galaxies and... Read More about Galaxies in the EAGLE hydrodynamical simulation and in the Durham and Munich semi-analytical models.

The Copernicus Complexio: a high-resolution view of the small-scale Universe (2016)
Journal Article
Hellwing, W., Frenk, C., Cautun, M., Bose, S., Helly, J., Jenkins, A., …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

We introduce Copernicus Complexio (COCO), a high-resolution cosmological N-body simulation of structure formation in the ΛCDM model. COCO follows an approximately spherical region of radius ∼17.4 h−1 Mpc embedded in a much larger periodic cube that i... Read More about The Copernicus Complexio: a high-resolution view of the small-scale Universe.

A new methodology to test galaxy formation models using the dependence of clustering on stellar mass (2015)
Journal Article
Campbell, D., Baugh, C., Mitchell, P., Helly, J., Gonzalez-Perez, V., Lacey, C., …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

We present predictions for the two-point correlation function of galaxy clustering as a function of stellar mass, computed using two new versions of the GALFORM semi-analytic galaxy formation model. These models make use of a high resolution, large v... Read More about A new methodology to test galaxy formation models using the dependence of clustering on stellar mass.

N-body dark matter haloes with simple hierarchical histories (2014)
Journal Article
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

We present a new algorithm which groups the subhaloes found in cosmological N-body simulations by structure finders such as SUBFIND into dark matter haloes whose formation histories are strictly hierarchical. One advantage of these `Dhaloes' over the... Read More about N-body dark matter haloes with simple hierarchical histories.

Simulations of the formation, evolution and clustering of galaxies and quasars (2005)
Journal Article
Springel, V., White, S., Jenkins, A., Frenk, C., Yoshida, N., Gao, L., …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

The cold dark matter model has become the leading theoretical picture for the formation of structure in the Universe. This model, together with the theory of cosmic inflation, makes a clear prediction for the initial conditions for structure formatio... Read More about Simulations of the formation, evolution and clustering of galaxies and quasars.

Galaxy formation using halo merger histories taken from N-body simulations (2003)
Journal Article
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

We develop a hybrid galaxy formation model that uses outputs from an N-body simulation to follow the merger histories (or ‘merger trees’) of dark matter haloes and treats baryonic processes, such as the cooling of gas within haloes and subsequent sta... Read More about Galaxy formation using halo merger histories taken from N-body simulations.

A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation (2003)
Journal Article
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

We compare the results of two techniques used to calculate the evolution of cooling gas during galaxy formation: smooth particle hydrodynamics (SPH) simulations and semi-analytic modelling. We improve upon the earlier statistical comparison of Benson... Read More about A comparison of gas dynamics in smooth particle hydrodynamics and semi-analytic models of galaxy formation.