Publications

This page lists publications using COLT, with separate sections for related methodology and science papers. The Algorithms page connects selected methods to their current implementation and assumptions, while the Developer notes page describes code ownership and runtime conventions.

Original Methods Paper

• Smith, A., Safranek-Shrader, C., Bromm, V., Milosavljević, M., 2015, MNRAS, 449, 4336: ‘The Lyman α signature of the first galaxies’ (arXiv:1409.4480)

  Introduces COLT’s Monte Carlo Lyα transfer methods and validation tests, with predictions for the first galaxies.

Additional Methods Papers

These papers describe numerical implementations and benchmarks involving COLT, or analytical solutions and insights tested with COLT.

• Kasiri, J., Smith, A., Lorinc, K., Nebrin, O., Kimura, K., 2026, preprint: ‘Force convergence in Monte Carlo Lyman-alpha radiative transfer’ (arXiv:2607.08726)

  Tests scattering, energy-gradient, and pressure-divergence force estimators in COLT against diffusion-limit solutions. Develops convergence diagnostics that distinguish estimator bias, sampling uncertainty, and the reliability of that uncertainty.

• Stace, E., Smith, A., Lorinc, K., Nebrin, O., 2026, PASA, 43, e015: ‘Multi-resonant-line radiative transfer: Lyman-Alpha fine structure and deuterium coupling’ (arXiv:2511.20580)

  Implements coupled resonance-line scattering in COLT and derives analytical solutions for V-shaped atomic networks in slabs and spheres. Applies these benchmarks to Lyα fine structure and hydrogen–deuterium coupling.

• Lorinc, K., Smith, A., Nebrin, O., Kasiri, J., 2025, preprint: ‘Core-wing transitions and the breakdown of diffusion in Lyman-α radiative transfer’ (arXiv:2512.09031)

  Uses COLT to test analytical descriptions of internal Lyα radiation fields and identify failures of diffusion approximations. Examines core–wing transitions and the effects of core-skipping on momentum transfer.

• McClymont, W., Smith, A., Tacchella, S., 2025, preprint: ‘Modelling the nebular emission of galaxies across cosmic time with COLT’ (arXiv:2510.13952)

  Introduces COLT’s coupled thermal-equilibrium and ionization solvers, metal level-population calculations, and nebular continuum emission. Validates the resulting line emission and applies it to galaxies across cosmic time.

• Smith, A., Lorinc, K., Nebrin, O., Lao, B.-X., 2025, MNRAS, 541, 179: ‘Lyman α resonant-line radiative transfer in expanding media’ (arXiv:2501.01928)

  Derives analytical Lyα transfer solutions in expanding clouds and cosmological flows. Implements continuous Doppler shifting and gridless Monte Carlo transport in COLT to test the solutions and their diffusion limits.

• Nebrin, O., Smith, A., Lorinc, K., Hörnquist, J., Larson, Å., Mellema, G., Giri, S. K., 2025, MNRAS, 537, 1646: ‘Lyman-α feedback prevails at Cosmic Dawn: implications for the first galaxies, stars, and star clusters’ (arXiv:2409.19288)

  Derives Lyα radiation-force solutions including absorption, velocity gradients, photon destruction, turbulence, and recoil, with COLT validation. Provides a force-multiplier fit for feedback models of early star formation.

• Smith, A., Kannan, R., Tacchella, S., Vogelsberger, M., Hernquist, L., Marinacci, F., Sales, L.V., Torrey, P., Li, H., Yeh, J. Y.-C., Qi, J., 2022, MNRAS, 517, 1: ‘The physics of Lyman-α escape from disc-like galaxies’ (arXiv:2111.13721)

  Introduces COLT’s photoionization-equilibrium solver and self-consistent hydrogen-line emission, including dust and helium processing of ionizing photons. Applies these methods to Lyα escape from simulated disc galaxies.

• Lao, B.-X., Smith, A., 2020, MNRAS, 497, 3925: ‘Resonant-line radiative transfer within power-law density profiles’ (arXiv:2005.09692)

  Derives analytical resonant-line transfer solutions for power-law density and emissivity profiles. Tests them with a gridless COLT variant that integrates optical depths through spatially varying media.

• Smith, A., Tsang, B. T.-H., Bromm, V., Milosavljević, M., 2018, MNRAS, 479, 2065: ‘Discrete diffusion Lyman α radiative transfer’ (arXiv:1709.10187)

  Develops resonant discrete-diffusion Monte Carlo transport to accelerate optically thick Lyα calculations. Derives analytical benchmarks and compares accuracy and cost with COLT’s standard Monte Carlo transport.

• Smith, A., Becerra, F., Bromm, V., Hernquist, L., 2017, MNRAS, 472, 205: ‘Radiative effects during the assembly of direct collapse black holes’ (arXiv:1706.02751)

  Extends COLT to ray tracing through native Voronoi meshes and applies path-based radiation-force estimators to a forming direct-collapse black hole.

• Smith, A., Bromm, V., Loeb, A., 2017, MNRAS, 464, 2963: ‘Lyman α radiation hydrodynamics of galactic winds before cosmic reionization’ (arXiv:1607.07166)

  Couples COLT to spherical Lagrangian hydrodynamics, including ionizing radiation and Lyα momentum deposition. Tests radiation transport and studies Lyα-driven winds before reionization.

Related Methodology

• Kapoor, A. U., Baes, M., Smith, A., Lauwers, A., Gebek, A., Camps, P., De Rijcke, S., van der Wel, A., Matsumoto, K., McClymont, W., 2026, preprint: ‘Predicting ionised gas emission in 3D with SKIRT. I. Framework and validation’ (arXiv:2607.09961)

  Benchmarks three-dimensional nebular emission against COLT while introducing SKIRT’s ionized-gas module, comparing line luminosities, maps, and diagnostic ratios.

• Smith, A., Kannan, R., Tsang, B. T.-H., Vogelsberger, M., Pakmor, R., 2020, ApJ, 905, 27: ‘AREPO-MCRT: Monte Carlo Radiation Hydrodynamics on a Moving Mesh’ (arXiv:2008.01750)

  Develops moving-mesh Monte Carlo radiation hydrodynamics in AREPO, including implicit transport and discrete diffusion. Appendix A derives radial momentum deposition with continuous absorption, which is the approach adopted by COLT’s radial path estimators.

Science Papers

• Naidu, R. P., Matthee, J., Katz, H., de Graaff, A., Oesch, P. A., Smith, A., Greene, J. E., Brammer, G., Weibel, A., Hviding, R., Chisholm, J., Labbé, I., Simcoe, R. A., Witten, C., Sun, W. Q., Atek, H., Baggen, J. F. W., Belli, S., Bezanson, R., Boogaard, L. A., Bose, S., Bouwens, R. J., Covelo-Paz, A., Dayal, P., Fudamoto, Y., Furtak, L. J., Giovinazzo, E., Goulding, A., Gronke, M., Heintz, K. E., Hirschmann, M., Illingworth, G., Inoue, A. K., Johnson, B. D., Leja, J., Leonova, E., McConachie, I., Maseda, M. V., Natarajan, P., Nelson, E., Setton, D. J., Shivaei, I., Sobral, D., Stefanon, M., Tacchella, S., Toft, S., Torralba, A., van Dokkum, P., van der Wel, A., Volonteri, M., Walter, F., Wang, B., Watson, D., Whitaker, K., 2026, Nature, 656, 329: ‘A gas-enshrouded and gas-reddened black hole at cosmic dawn’ (arXiv:2503.16596)

  Uses COLT shell models of Hβ scattering to interpret the complex Balmer-line profiles of a gas-enshrouded black hole at cosmic dawn.

• Bennett, J. S., Smith, A., Arrigoni-Battaia, F., Sijacki, D., Lochhaas, C., Hernquist, L., 2026, The Open Journal of Astrophysics, 9: ‘The birth of the intracluster medium: the evolution of multiphase gas and Lyman-α haloes in a simulated z ∼ 3 protocluster’ (arXiv:2603.16991)

  Models Lyα and Hα haloes with COLT to trace the transformation of a protocluster’s multiphase gas into the intracluster medium.

• Nebrin, O., Smith, A., Mellema, G., Lorinc, K., Manzoni, D., 2026, preprint: ‘Lyman-alpha Pressure Strongly Enhances Pre-Supernova Feedback at Cosmic Dawn: The First Multi-Dimensional Lyman-alpha Radiation Hydrodynamics Simulations’ (arXiv:2606.02711)

  Uses COLT benchmarks to validate Lydion’s Lyα solver before studying radiation-pressure feedback in two-dimensional simulations of metal-poor clouds.

• Summerfield, Z., McClymont, W., Tacchella, S., Smith, A., Kannan, R., Garaldi, E., Puchwein, E., Shen, X., Borrow, J., Danhaive, A. L., Keating, L., Maheson, G., Mehrotra, P., Simmonds, C., Stoffers, A., Vogelsberger, M., Zier, O., 2026, preprint: ‘From THESAN-ZOOM to JWST: Predicting ionizing photon escape and the rise of UV-bright reionization sources’ (arXiv:2606.14671)

  Uses COLT predictions for THESAN-ZOOM galaxies to identify observable diagnostics of ionizing-photon escape and reconstruct reionization histories.

• McClymont, W., Tacchella, S., Smith, A., Kannan, R., Garaldi, E., Puchwein, E., Isobe, Y., Ji, X., Shen, X., Wang, Z., Belokurov, V., Borrow, J., D’Eugenio, F., Keating, L., Maiolino, R., Monty, S., Vogelsberger, M., Zier, O., 2026, MNRAS, 548, stag016: ‘The THESAN-ZOOM project: mystery N/O more – uncovering the origin of peculiar chemical abundances and a not-so-fundamental metallicity relation at 3 < z < 12’ (arXiv:2507.08787)

  Uses synthetic Balmer emission to connect nitrogen-rich THESAN-ZOOM galaxies and their chemical enrichment histories to high-redshift observations.

• Menon, S. H., Smith, A., 2026, preprint: ‘Lyman-alpha Radiation Pressure in Dense Star Clusters: Implications for Star Formation and Winds at Cosmic Dawn’ (arXiv:2605.13982)

  Post-processes turbulent, cluster-forming clouds with COLT to assess how dust regulates Lyα radiation pressure, star formation, and winds.

• Chen, K.-F., Neyer, M., Hewitt, J. N., Smith, A., Vogelsberger, M., 2026, ApJ, 1001, 186: ‘Stacking 21 cm Maps around Lyα Emitters during Reionization: Prospects for a Cross-correlation Detection with the Hydrogen Epoch of Reionization Array’ (arXiv:2510.07374)

  Uses THESAN Lyα-emitter predictions based on COLT sightlines to forecast 21-cm stacking measurements with HERA.

• Sitaram, M., Li, H., Zheng, Y., Bryan, G. L., Putman, M., Smith, A., Kannan, R., 2026, ApJ, 1001, 87: ‘Identifying Signatures of Inflow onto Face-on Galaxies Using the Balmer Decrement’ (arXiv:2604.05141)

  Tests whether the Balmer decrement can distinguish foreground inflow from background outflow using synthetic Hα and Hβ data cubes.

• Lucchini, S., Abramson, C., Hummels, C., Conroy, C., Hernquist, L., Smith, A., 2026, preprint: ‘ENhanced Galactic Atmospheres With Arepo: Resolving the CGM at 200 pc with the ENGAWA Simulations’ (arXiv:2603.05584)

  Recalculates circumgalactic ion populations with COLT to assess how stellar radiation changes absorption predictions in the ENGAWA simulations.

• McClymont, W., Tacchella, S., Smith, A., Kannan, R., Puchwein, E., Borrow, J., Garaldi, E., Keating, L., Vogelsberger, M., Zier, O., Shen, X., Popovic, F., 2025, MNRAS, 544, 1732: ‘The THESAN-ZOOM project: central starbursts and inside-out quenching govern galaxy sizes in the early Universe’ (arXiv:2503.04894)

  Uses synthetic Hα and UV observations to connect high-redshift galaxy sizes to central starbursts and inside-out quenching.

• Garaldi, E., Bellscheidt, V., Smith, A., Kannan, R., 2025, The Open Journal of Astrophysics, 8: ‘The galaxy-IGM connection in THESAN: observability and information content of the galaxy-Lyman-α cross-correlation at z ≥ 6’ (arXiv:2410.02850)

  Uses COLT-extracted sightlines to assess the observability and information content of galaxy–Lyα forest correlations during reionization.

• McClymont, W., Tacchella, S., Smith, A., Kannan, R., Puchwein, E., Borrow, J., Garaldi, E., Keating, L., Vogelsberger, M., Zier, O., Shen, X., Popovic, F., Simmonds, C., 2025, MNRAS, 544, 513: ‘The THESAN-ZOOM project: burst, quench, repeat – unveiling the evolution of high-redshift galaxies along the star-forming main sequence’ (arXiv:2503.00106)

  Uses synthetic Hα and UV luminosities to connect bursty star formation to the observed scatter of the high-redshift star-forming main sequence.

• Kannan, R., Puchwein, E., Smith, A., Borrow, J., Garaldi, E., Keating, L., Vogelsberger, M., Zier, O., McClymont, W., Shen, X., Popovic, F., Tacchella, S., Hernquist, L., Springel, V., 2025, The Open Journal of Astrophysics, 8: ‘Introducing the THESAN-ZOOM project: radiation-hydrodynamic simulations of high-redshift galaxies with a multi-phase interstellar medium’ (arXiv:2502.20437)

  Computes dust-attenuated UV emission for THESAN-ZOOM and compares its high-redshift galaxy luminosity functions with observations.

• Neyer, M., Smith, A., Vogelsberger, M., García, L. Á., Kannan, R., Garaldi, E., Keating, L., 2025, preprint: ‘The THESAN project: Lyman-alpha emitters as probes of ionized bubble sizes’ (arXiv:2510.18946)

  Uses COLT sightlines through THESAN to relate Lyα-emitter visibility to ionized bubble sizes.

• Carr, C. A., Smith, A., Pandya, V., Hayward, C. C., Huberty, M., Scarlata, C., Cen, R., 2025, ApJ, 990, 220: ‘Evaluating Mass Outflow Rate Estimators in FIRE-2 Simulations: Toward a Self-consistent Framework for Spectral-line-based Predictions’ (arXiv:2503.22312)

  Uses synthetic Si II spectra from FIRE-2 galaxies to test how reliably absorption-line models recover galactic outflow properties.

• Garaldi, E., Bellscheidt, V., Smith, A., Kannan, R., 2025, The Open Journal of Astrophysics, 8: ‘The galaxy-IGM connection in THESAN: the physics connecting the IGM Lyman-α opacity and galaxy density in the reionization epoch’ (arXiv:2410.02853)

  Uses COLT-extracted sightlines to explain how ionizing radiation and gas density shape galaxy–Lyα forest correlations during reionization.

• McClymont, W., Tacchella, S., Smith, A., Kannan, R., Maiolino, R., Belfiore, F., Hernquist, L., Li, H., Vogelsberger, M., 2024, MNRAS, 532, 2016: ‘The nature of diffuse ionized gas in star-forming galaxies’ (arXiv:2403.03243)

  Models ionization and optical line emission to identify the stellar sources and physical conditions of diffuse ionized gas.

• Garaldi, E., Kannan, R., Smith, A., Borrow, J., Vogelsberger, M., Pakmor, R., Springel, V., Hernquist, L., Galárraga-Espinosa, D., Yeh, J. Y.-C., Shen, X., Xu, C., Neyer, M., Spina, B., Almualla, M., Zhao, Y., 2024, MNRAS, 530, 3765: ‘The THESAN project: public data release of radiation-hydrodynamic simulations matching reionization-era JWST observations’ (arXiv:2309.06475)

  Releases THESAN data products, including COLT-extracted sightlines and ionizing-photon escape catalogues.

• Xu, C., Smith, A., Borrow, J., Garaldi, E., Kannan, R., Vogelsberger, M., Pakmor, R., Springel, V., Hernquist, L., 2023, MNRAS, 521, 4356: ‘The THESAN project: Lyman-α emitter luminosity function calibration’ (arXiv:2210.16275)

  Calibrates Lyα-emitter luminosity functions by combining galaxy-scale emission models with intergalactic transmission through THESAN.

• Yeh, J. Y.-C., Smith, A., Kannan, R., Garaldi, E., Vogelsberger, M., Borrow, J., Pakmor, R., Springel, V., Hernquist, L., 2023, MNRAS, 520, 2757: ‘The THESAN project: ionizing escape fractions of reionization-era galaxies’ (arXiv:2205.02238)

  Measures ionizing-photon escape from THESAN galaxies and its dependence on galaxy properties and direction.

• Jahn, E. D., Sales, L. V., Marinacci, F., Vogelsberger, M., Torrey, P., Qi, J., Smith, A., Li, H., Kannan, R., Burger, J. D., Zavala, J., 2023, MNRAS, 520, 461: ‘Real and counterfeit cores: how feedback expands haloes and disrupts tracers of inner gravitational potential in dwarf galaxies’ (arXiv:2110.00142)

  Uses COLT projections to visualize dwarf galaxies while studying feedback-driven cores and biases in gas-kinematic tracers.

• Tacchella, S., Smith, A., Kannan, R., Marinacci, F., Hernquist, L., Vogelsberger, M., Torrey, P., Sales, L., Li, H., 2022, MNRAS, 513, 2904: ‘Hα emission in local galaxies: star formation, time variability, and the diffuse ionized gas’ (arXiv:2112.00027)

  Models Hα emission to study star-formation indicators, time variability, and the contribution of diffuse ionized gas.

• Garaldi, E., Kannan, R., Smith, A., Springel, V., Pakmor, R., Vogelsberger, M., Hernquist, L., 2022, MNRAS, 512, 4909: ‘The THESAN project: properties of the intergalactic medium and its connection to reionization-era galaxies’ (arXiv:2110.01628)

  Uses synthetic intergalactic sightlines to connect Lyα transmission statistics with reionization-era galaxies.

• Smith, A., Kannan, R., Garaldi, E., Vogelsberger, M., Pakmor, R., Springel, V., Hernquist, L., 2022, MNRAS, 512, 3243: ‘The THESAN project: Lyman-α emission and transmission during the Epoch of Reionization’ (arXiv:2110.02966)

  Predicts intrinsic Lyα emission and intergalactic transmission for galaxies throughout reionization in THESAN.

• Kimock, B., Narayanan, D., Smith, A., Ma, X., Feldmann, R., Anglés-Alcázar, D., Bromm, V., Davé, R., Geach, J., Hopkins, P., Kereš, D., 2021, ApJ, 909, 119: ‘The Origin and Evolution of Lyman-α Blobs in Cosmological Galaxy Formation Simulations’ (arXiv:2004.08397)

  Uses Lyα radiative transfer through cosmological simulations to investigate the origin and evolution of extended Lyα blobs.

• Yang, Y.-L., Evans, N. J., Smith, A., Lee, J.-E., Tobin, J. J., Terebey, S., Calcutt, H., Jørgensen, J. K., Green, J. D., Bourke, T. L., 2020, ApJ, 891, 61: ‘Constraining the Infalling Envelope Models of Embedded Protostars: BHR 71 and Its Hot Corino’ (arXiv:2002.01478)

  Uses LIME-AID, a COLT-based molecular-line ray tracer, to constrain BHR 71’s infalling envelope and hot corino.

• Smith, A., Ma, X., Bromm, V., Finkelstein, S. L., Hopkins, P. F., Faucher-Giguère, C.-A., Kereš, D., 2019, MNRAS, 484, 39: ‘The physics of Lyman α escape from high-redshift galaxies’ (arXiv:1810.08185)

  Models Lyα escape from high-redshift FIRE galaxies, including the effects of gas kinematics, dust, and viewing direction.

• Smith, A., Bromm, V., Loeb, A., 2016, MNRAS, 460, 3143: ‘Evidence for a direct collapse black hole in the Lyman α source CR7’ (arXiv:1602.07639)

  Tests whether Lyα emission and its velocity offset in CR7 can be explained by an accreting direct-collapse black hole.