Harley Katz

Beecroft Fellow · Co-founder of Probably Genetic · Forbes 30 Under 30 · PhD Astrophysics · harley.katz@physics.ox.ac.uk

In short, I tackle hard problems with large computers.

Current Projects

Feel free to reach out for collaboration on any of these topics.

MEGATRON

Transforming our understanding of the ISM and CGM with RAMSES-RTZ

Awarded >50M CPUh on the UK's DiRAC facilities, MEGATRON is the first cosmological simulation to self-consistently model the non-equilibrium chemistry and heating/cooling processes in the interstellar medium for nearly 100 atoms, ions, and molecules coupled to on-the-fly radiation transfer. Complete with state-of-the-art modules for galaxy formation and stellar feedback, including the formation and enrichment from Population III stars, MEGATRON models the formation of a Milky Way-like galaxy from the earliest epochs until cosmic noon.

SPHINX20 Public Data Release

Apples-to-apples comparisons between high-redshift simulations and JWST observations

An ambitious project to completely forward-model the spectra and photometry from the largest full-box cosmological radiation hydrodynamcis simulation of reionization with a resolved ISM.

Exascale Gravity

A new gravity algorithm without all-to-all communication

The next generation of exascale codes require us to rethink even our most basic algorithms. This project is in its infant stages and uses a purely-local method to solve gravity in a cosmological setting.

Education

University of Cambridge

PhD in Astrophysics
October 2013 - September 2017

University of Maryland, College Park

Double Degree, BS in Physics, BS in Astronomy
August 2009 - May 2013

Astrophysics Publications

First-Author
  • Katz, H., Kimm, T., Ellis, R. S., Devriendt, J., & Slyz, A., 'The challenges of identifying Population III stars in the early Universe', MNRAS, 524, 351 (2023).
  • Katz, H., Saxena, A., Cameron, A. J., Carniani, S., Bunker, A. J., Arribas, S., Bhatawdekar, R., Bowler, R. A. A., Boyett, K. N. K., Cresci, G., Curtis-Lake, E., D'Eugenio, F., Kumari, N., Looser, T. J., Maiolino, R., Übler, H., Willott, C., & Witstok, J., 'First insights into the ISM at z > 8 with JWST: possible physical implications of a high [O III] λ4363/[O III] λ5007', MNRAS, 518, 592 (2023).
  • Katz, H., Saxena, A., Rosdahl, J., Kimm, T., Blaizot, J., Garel, T., Michel-Dansac, L., Haehnelt, M., Ellis, R. S., Pentericci, L., Devriendt, J., & Slyz, A., 'Two modes of LyC escape from bursty star formation: implications for [C II] deficits and the sources of reionization', MNRAS, 518, 270 (2023).
  • Katz, H., Liu, S., Kimm, T., Rey, M. P., Andersson, E. P., Cameron, A. J., Rodriguez-Montero, F., Agertz, O., Devriendt, J., & Slyz, A., 'PRISM: A Non-Equilibrium, Multiphase Interstellar Medium Model for Radiation Hydrodynamics Simulations of Galaxies', arXiv, arXiv:2211.04626 (2022).
  • Katz, H., Garel, T., Rosdahl, J., Mauerhofer, V., Kimm, T., Blaizot, J., Michel-Dansac, L., Devriendt, J., Slyz, A., & Haehnelt, M., 'Mg II in the JWST era: a probe of Lyman continuum escape?', MNRAS, 515, 4265 (2022).
  • Katz, H., 'RAMSES-RTZ: non-equilibrium metal chemistry and cooling coupled to on-the-fly radiation hydrodynamics', MNRAS, 512, 348 (2022).
  • Katz, H., Rosdahl, J., Kimm, T., Garel, T., Blaizot, J., Haehnelt, M. G., Michel-Dansac, L., Martin-Alvarez, S., Devriendt, J., Slyz, A., Teyssier, R., Ocvirk, P., Laporte, N., & Ellis, R., 'The nature of high [O III]88 μ m/[C II]158 μm galaxies in the epoch of reionization: Low carbon abundance and a top-heavy IMF?', MNRAS, 510, 5603 (2022).
  • Katz, H., Martin-Alvarez, S., Rosdahl, J., Kimm, T., Blaizot, J., Haehnelt, M. G., Michel-Dansac, L., Garel, T., Oñorbe, J., Devriendt, J., Slyz, A., Attia, O., & Teyssier, R., 'Introducing SPHINX-MHD: the impact of primordial magnetic fields on the first galaxies, reionization, and the global 21-cm signal', MNRAS, 507, 1254 (2021).
  • Katz, H., Ďurovčíková, D., Kimm, T., Rosdahl, J., Blaizot, J., Haehnelt, M. G., Devriendt, J., Slyz, A., Ellis, R., & Laporte, N., 'New methods for identifying Lyman continuum leakers and reionization-epoch analogues', MNRAS, 498, 164 (2020).
  • Katz, H., Ramsoy, M., Rosdahl, J., Kimm, T., Blaizot, J., Haehnelt, M. G., Michel-Dansac, L., Garel, T., Laigle, C., Devriendt, J., & Slyz, A., 'How to quench a dwarf galaxy: The impact of inhomogeneous reionization on dwarf galaxies and cosmic filaments', MNRAS, 494, 2200 (2020).
  • Katz, H., Galligan, T. P., Kimm, T., Rosdahl, J., Haehnelt, M. G., Blaizot, J., Devriendt, J., Slyz, A., Laporte, N., & Ellis, R., 'Probing cosmic dawn with emission lines: predicting infrared and nebular line emission for ALMA and JWST', MNRAS, 487, 5902 (2019).
  • Katz, H., Laporte, N., Ellis, R. S., Devriendt, J., & Slyz, A., 'Probing cosmic dawn: modelling the assembly history, SEDs, and dust content of selected z ∼ 9 galaxies', MNRAS, 484, 4054 (2019).
  • Katz, H., Martin-Alvarez, S., Devriendt, J., Slyz, A., & Kimm, T., 'Magnetogenesis at Cosmic Dawn: tracing the origins of cosmic magnetic fields', MNRAS, 484, 2620 (2019).
  • Katz, H., Desmond, H., McGaugh, S., & Lelli, F., 'The tight empirical relation between dark matter halo mass and flat rotation velocity for late-type galaxies', MNRAS, 483, L98 (2019).
  • Katz, H., Kimm, T., Haehnelt, M. G., Sijacki, D., Rosdahl, J., & Blaizot, J., 'Tracing the sources of reionization in cosmological radiation hydrodynamics simulations', MNRAS, 483, 1029 (2019).
  • Katz, H., Desmond, H., Lelli, F., McGaugh, S., Di Cintio, A., Brook, C., & Schombert, J., 'Stellar feedback and the energy budget of late-type Galaxies: missing baryons and core creation', MNRAS, 480, 4287 (2018).
  • Katz, H., Kimm, T., Haehnelt, M., Sijacki, D., Rosdahl, J., & Blaizot, J., 'A Census of the LyC photons that form the UV background during reionization', MNRAS, 478, 4986 (2018).
  • Katz, H., Kimm, T., Sijacki, D., & Haehnelt, M. G., 'Interpreting ALMA observations of the ISM during the epoch of reionization', MNRAS, 468, 4831 (2017).
  • Katz, H., Lelli, F., McGaugh, S. S., Di Cintio, A., Brook, C. B., & Schombert, J. M., 'Testing feedback-modified dark matter haloes with galaxy rotation curves: estimation of halo parameters and consistency with ΛCDM scaling relations', MNRAS, 466, 1648 (2017).
  • Katz, H., Sijacki, D., & Haehnelt, M. G., 'Seeding high-redshift QSOs by collisional runaway in primordial star clusters', MNRAS, 451, 2352 (2015).
  • Katz, H., Sijacki, D., & Haehnelt, M., 'Seeding High Redshift QSOs by Collisional Runaway in Primordial Star Clusters', IAUGA, 29, 2230030 (2015).
  • Katz, H., & Ricotti, M., 'Clues on the missing sources of reionization from self-consistent modelling of Milky Way and dwarf galaxy globular clusters', MNRAS, 444, 2377 (2014).
  • Katz, H., McGaugh, S. S., Sellwood, J. A., & de Blok, W. J. G., 'The formation of spiral galaxies: adiabatic compression with Young's algorithm and the relation of dark matter haloes to their primordial antecedents', MNRAS, 439, 1897 (2014).
  • Katz, H., & Ricotti, M., 'Two epochs of globular cluster formation from deep field luminosity functions: implications for reionization and the Milky Way satellites', MNRAS, 432, 3250 (2013).
  • Katz, H., McGaugh, S., Teuben, P., & Angus, G. W., 'Galaxy Cluster Bulk Flows and Collision Velocities in QUMOND', ApJ, 772, 10 (2013).

Latter-Author
  • Blaizot, J., Garel, T., Verhamme, A., Katz, H., Kimm, T., Michel-Dansac, L., Mitchell, P. D., Rosdahl, J., & Trebitsch, M., 'Simulating the diversity of shapes of the Lyman-α line', MNRAS, 523, 3749 (2023).
  • Cameron, A. J., Katz, H., Rey, M. P., & Saxena, A., 'Nitrogen enhancements 440 Myr after the big bang: supersolar N/O, a tidal disruption event, or a dense stellar cluster in GN-z11?', MNRAS, 523, 3516 (2023).
  • Cameron, A. J., Katz, H., & Rey, M. P., 'A novel approach to correcting Te-based mass-metallicity relations', MNRAS, 522, L89 (2023).
  • Steinhardt, C. L., Sneppen, A., Clausen, T., Katz, H., Rey, M. P., & Stahlschmidt, J., 'The Highest-Redshift Balmer Breaks as a Test of ΛCDM', arXiv, arXiv:2305.15459 (2023).
  • Choustikov, N., Katz, H., Saxena, A., Cameron, A. J., Devriendt, J., Slyz, A., Rosdahl, J., Blaizot, J., & Michel-Dansac, L., 'The Physics of Indirect Estimators of Lyman Continuum Escape and their Application to High-Redshift JWST Galaxies', arXiv, arXiv:2304.08526 (2023).
  • Witten, C., Laporte, N., Martin-Alvarez, S., Sijacki, D., Yuan, Y., Haehnelt, M. G., Baker, W., Dunlop, J. S., Ellis, R. S., Grogin, N., Illingworth, G., Katz, H., Koekemoer, A. M., Magee, D., Maiolino, R., McClymont, W., Pérez-González, P. G., Puskas, D., Roberts-Borsani, G., Santini, P., & Simmonds, C., 'Deciphering Lyman-α Emission Deep into the Epoch of Reionisation', arXiv, arXiv:2303.16225 (2023).
  • Rey, M. P., Katz, H. B., Cameron, A. J., Devriendt, J., & Slyz, A., 'Boosting galactic outflows with enhanced resolution', arXiv, arXiv:2302.08521 (2023).
  • Witten, C. E. C., Laporte, N., & Katz, H., 'Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7', ApJ, 944, 61 (2023).
  • Saxena, A., Cryer, E., Ellis, R. S., Pentericci, L., Calabrò, A., Mascia, S., Saldana-Lopez, A., Schaerer, D., Katz, H., Llerena, M., & Amorín, R., 'Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape', MNRAS, 517, 1098 (2022).
  • Rosdahl, J., Blaizot, J., Katz, H., Kimm, T., Garel, T., Haehnelt, M., Keating, L. C., Martin-Alvarez, S., Michel-Dansac, L., & Ocvirk, P., 'LyC escape from SPHINX galaxies in the Epoch of Reionization', MNRAS, 515, 2386 (2022).
  • Han, D., Kimm, T., Katz, H., Devriendt, J., & Slyz, A., 'Impact of Radiation Feedback on the Formation of Globular Cluster Candidates during Cloud-Cloud Collisions', ApJ, 935, 53 (2022).
  • Martin-Alvarez, S., Devriendt, J., Slyz, A., Sijacki, D., Richardson, M. L. A., & Katz, H., 'Towards convergence of turbulent dynamo amplification in cosmological simulations of galaxies', MNRAS, 513, 3326 (2022).
  • Maji, M., Verhamme, A., Rosdahl, J., Garel, T., Blaizot, J., Mauerhofer, V., Pittavino, M., Victoria Feser, M.-P., Chuniaud, M., Kimm, T., Katz, H., & Haehnelt, M., 'Predicting Lyman-continuum emission of galaxies using their physical and Lyman-α emission properties', A&A, 663, A66 (2022).
  • Lee, J., Kimm, T., Blaizot, J., Katz, H., Lee, W., Sheen, Y.-K., Devriendt, J., & Slyz, A., 'Simulating Jellyfish Galaxies: A Case Study for a Gas-rich Dwarf Galaxy', ApJ, 928, 144 (2022).
  • Trebitsch, M., Dubois, Y., Volonteri, M., Pfister, H., Cadiou, C., Katz, H., Rosdahl, J., Kimm, T., Pichon, C., Beckmann, R. S., Devriendt, J., & Slyz, A., 'The OBELISK simulation: Galaxies contribute more than AGN to H I reionization of protoclusters', A&A, 653, A154 (2021).
  • Martin-Alvarez, S., Katz, H., Sijacki, D., Devriendt, J., & Slyz, A., 'Unravelling the origin of magnetic fields in galaxies', MNRAS, 504, 2517 (2021).
  • Attia, O., Teyssier, R., Katz, H., Kimm, T., Martin-Alvarez, S., Ocvirk, P., & Rosdahl, J., 'Cosmological magnetogenesis: the Biermann battery during the Epoch of reionization', MNRAS, 504, 2346 (2021).
  • Garel, T., Blaizot, J., Rosdahl, J., Michel-Dansac, L., Haehnelt, M. G., Katz, H., Kimm, T., & Verhamme, A., 'Ly α as a tracer of cosmic reionization in the SPHINX radiation-hydrodynamics cosmological simulation', MNRAS, 504, 1902 (2021).
  • Lee, J., Kimm, T., Katz, H., Rosdahl, J., Devriendt, J., & Slyz, A., 'Dual Effects of Ram Pressure on Star Formation in Multiphase Disk Galaxies with Strong Stellar Feedback', ApJ, 905, 31 (2020).
  • Ďurovčíková, D., Katz, H., Bosman, S. E. I., Davies, F. B., Devriendt, J., & Slyz, A., 'Reionization history constraints from neural network based predictions of high-redshift quasar continua', MNRAS, 493, 4256 (2020).
  • Laporte, N., Katz, H., Ellis, R. S., Lagache, G., Bauer, F. E., Boone, F., Inoue, A. K., Hashimoto, T., Matsuo, H., Mawatari, K., & Tamura, Y., 'The absence of [C II] 158 μm emission in spectroscopically confirmed galaxies at z > 8', MNRAS, 487, L81 (2019).
  • Kimm, T., Blaizot, J., Garel, T., Michel-Dansac, L., Katz, H., Rosdahl, J., Verhamme, A., & Haehnelt, M., 'Understanding the escape of LyC and Lyα photons from turbulent clouds', MNRAS, 486, 2215 (2019).
  • Lelli, F., McGaugh, S. S., Schombert, J. M., Desmond, H., & Katz, H., 'The baryonic Tully-Fisher relation for different velocity definitions and implications for galaxy angular momentum', MNRAS, 484, 3267 (2019).
  • Desmond, H., Katz, H., Lelli, F., & McGaugh, S., 'Uncorrelated velocity and size residuals across galaxy rotation curves', MNRAS, 484, 239 (2019).
  • Galligan, T. P., Katz, H., Kimm, T., Rosdahl, J., Blaizot, J., Devriendt, J., & Slyz, A., 'deepCool: Fast and Accurate Estimation of Cooling Rates in Irradiated Gas with Artificial Neural Networks', arXiv, arXiv:1901.01264 (2019).
  • Rosdahl, J., Katz, H., Blaizot, J., Kimm, T., Michel-Dansac, L., Garel, T., Haehnelt, M., Ocvirk, P., & Teyssier, R., 'The SPHINX cosmological simulations of the first billion years: the impact of binary stars on reionization', MNRAS, 479, 994 (2018).
  • Kimm, T., Haehnelt, M., Blaizot, J., Katz, H., Michel-Dansac, L., Garel, T., Rosdahl, J., & Teyssier, R., 'Impact of Lyman alpha pressure on metal-poor dwarf galaxies', MNRAS, 475, 4617 (2018).
  • Kimm, T., Katz, H., Haehnelt, M., Rosdahl, J., Devriendt, J., & Slyz, A., 'Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization', MNRAS, 466, 4826 (2017).