Illuminating Galaxy Formation and Evolution

Accurate treatments of radiative processes help us understand observations and feedback effects.

My research focuses on understanding the nature of high-redshift galaxies, which is an important cosmic frontier encompassing a broad range of astrophysical phenomena. Currently, we have an exceptional window into the early Universe via precision measurements of the cosmic microwave background (CMB), providing the initial conditions for numerical simulations of cosmic structure formation. Complementary to this, we can probe back to roughly ~500 Myr after the Big Bang by way of highly sensitive telescopes, when the Universe already exhibited a complex landscape of stars, galaxies, and black hole activity. We will ultimately bridge the gap with increasingly sophisticated simulation approaches and next-generation ground- and space-based observatories. As a NASA Einstein Fellow with Mark Vogelsberger at MIT and previous NSF Graduate Research Fellow with Volker Bromm at UT Austin, I actively develop novel computational tools and theoretical models to address timely and critical questions about high-redshift galaxy formation and related fields.

Reionization Meets Galaxy Assembly

We aim to understand the nature of the first galaxies and the ensuing cosmic phase transition known as the Epoch of Reionization (EoR). I co-lead the THESAN and THESAN-ZOOMS simulation campaigns to produce realistic galaxies and synthetic observations, enabling a more fruitful exploitation of the forthcoming observational data. Please visit the dedicated website for more information:

Lyman-alpha Radiative Transfer

Lyα photons are a powerful probe of the interstellar medium (ISM) and circumgalactic medium (CGM) of high-redshift galaxies. I am the author of the Cosmic Lyman-alpha Transfer (COLT) code, which is a Monte Carlo radiative transfer (MCRT) solver for post-processing hydrodynamical simulations on arbitrary grids. COLT also includes several visualization and analysis tools that exploit the underlying ray-tracing algorithms or benefit from an efficient hybrid MPI + OpenMP parallelization strategy within a flexible C++ framework. The applications span multiple subfields in astrophysics and provide synergy with theory and observation. Please see the online documentation for more information:

MCRT Radiation Hydrodynamics

I recently developed AREPO-MCRT, a novel and accurate Monte Carlo radiation hydrodynamics solver for the moving-mesh code AREPO to enable studies of complex astrophysical phenomena. The method is designed for general multiple scattering problems and incorporates numerous improvements and noise reduction schemes to help overcome efficiency barriers that typically inhibit convergence. Please see the methods paper published in The Astrophysical Journal for more details.

Selected Publications

A complete list of my publications may be found in this NASA ADS Library.
ORCID iD: 0000-0002-2838-9033

  • Invited Reviews

    Smith, A., 2020, Nature Astronomy (News & Views), 4, 648: "Dynamics of Lyman-α blobs"
    Smith, A., Bromm, V., 2019, Contemporary Physics, 60, 111: "Supermassive black holes in the early universe"
    Smith, A., Bromm, V., Loeb, A., 2017, Astronomy & Geophysics, 58, 3.22: "The first supermassive black holes"

    Astronomy & Geophysics Cover

  • THESAN Release Papers

    Kannan, R., Smith, A., Garaldi, E., Shen, X., Vogelsberger, M., Pakmor, R., Springel, V., Hernquist, L., 2021, MNRAS, (arXiv:2111.02411): "The THESAN project: predictions for multi-tracer line intensity mapping in the Epoch of Reionization"
    Smith, A., Kannan, R., Garaldi, E., Vogelsberger, M., Pakmor, R., Springel, V., Hernquist, L., 2021, MNRAS, (arXiv:2110.02966): "The THESAN project: Lyman-α emission and transmission during the Epoch of Reionization"
    Garaldi, E., Kannan, R., Smith, A., Springel, V., Pakmor, R., Vogelsberger, M., Hernquist, L., 2021, MNRAS, (arXiv:2110.01628): "The THESAN project: properties of the intergalactic medium and its connection to Reionization-era galaxies"
    Kannan, R., Garaldi, E., Smith, A., Pakmor, R., Springel, V., Vogelsberger, M., Hernquist, L., 2021, MNRAS, (arXiv:2110.00584): "Introducing the THESAN project: radiation-magneto-hydrodynamic simulations of the Epoch of Reionization"

  • COLT Methods Papers

    Smith, A., Kannan, R., Tacchella, S., et al., 2021, MNRAS, (arXiv:2111.13721): "The physics of Lyman-α escape from disc-like galaxies"
    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"
    Smith, A., Safranek-Shrader, C., Bromm, V., Milosavljević, M., 2015, MNRAS, 449, 4336: "The Lyman-α signature of the first galaxies"

  • RHD Methods Papers

    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"
    Smith, A., Tsang, B. T.-H., Bromm, V., Milosavljević, M., 2018, MNRAS, 479, 2065: "Discrete diffusion Lyman-α radiative transfer"
    Smith, A., Bromm, V., Loeb, A., 2017, MNRAS, 464, 2963: "Lyman-α radiation hydrodynamics of galactic winds before cosmic reionization"

  • Direct Collapse Black Hole (DCBH) Papers

    Smith, A., Becerra, F., Bromm, V., Hernquist, L., 2017, MNRAS, 472, 205: "Radiative effects during the assembly of direct collapse black holes"
    Smith, A., Bromm, V., Loeb, A., 2016, MNRAS, 460, 3143: "Evidence for a direct collapse black hole in the Lyman-α source CR7"

  • Student-led Papers

    Kimock, B., Narayanan, D., Smith, A., Ma, X., Feldmann, R., et al., 2021, ApJ, 909, 119: "The Origin and Evolution of Lyman-α Blobs in Cosmological Galaxy Formation Simulations"
    Lao, B.-X., Smith, A., 2020, MNRAS, 497, 3925: "Resonant-line radiative transfer within power-law density profiles"

Contact Information

Feel free to reach out with any questions.

  • Photograph of Aaron Smith