UCSB Astrophysics
Portrait of Joseph Hennawi

§ 01People · Faculty

Joseph Hennawi

Professor

Joseph Hennawi is a cosmologist who works on both observation and theory. He often searches large sky surveys for rare objects to use as astrophysical laboratories and observes them with large telescopes. His focus is the diffuse gas of the intergalactic and circumgalactic media, which he studies with quasar absorption lines and cosmological simulations. Topics include reionization, the Lyman alpha forest and high redshift quasars.

He leads the ENIGMA group at UCSB and Leiden Observatory. His group set the record for the earliest known quasar in 2021. In 2026 a team led by his student used Euclid data to find 31 new early quasars, two of which broke that record.

He received his PhD from Princeton in 2004 and the Sofja Kovalevskaja Award in 2010, and led a Max Planck Research Group in Heidelberg before joining UCSB in 2016.

§ 02Fig. 1

Where in the universe

Range 7.9 Gly to 13.2 Gly

Joseph Hennawi, row of Fig. 1. The bar spans the light travel distances of the objects studied, 7.9 Gly to 13.2 Gly, on a logarithmic axis from the Solar System to the cosmic microwave background. Its color is the research theme. Dotted lines mark landmarks. Fig. 1 with every faculty member

§ 03Publications

Recent papers

The newest papers with Joseph Hennawi as an author, from NASA ADS. Group members are in gold.

  1. 01Sep 2026arXiv
    BAQARO: Tracing Stochastic Black Hole Growth Histories and Quasar Lightcurves in a Cosmological ContextE. Pizzati, J. F. Hennawi, J. SchayeCosmic dawn
    arXiv:2609.12061
  2. 02Aug 2026arXiv
    Quasar Impostors: Two Extremely UV-Bright (MUV≈−23.5) Reionisation-Epoch Galaxies Powered by Very Massive StarsD. Yang, J. F. Hennawi, S. E. I. Bosman, F. B. Davies, R. Bouwens, T. Kist, E. Bañados, J. Huang et al. (23 authors)Cosmic dawn
    arXiv:2608.18212
  3. 03Aug 2026MNRAS
    Using neural emulators and Hamiltonian Monte Carlo to constrain the epoch of reionization's history with the Lyα forest power spectrumD. González-Hernández, C. Doughty, M. Wolfson, J. F. Hennawi, Z. JinCosmic dawn
    arXiv:2509.13498
  4. 04Aug 2026MNRAS
    Inferring local quasar IGM damping wing constraintsT. Kist, J. F. Hennawi, F. B. DaviesCosmic dawn
    arXiv:2508.21812
  5. 05Aug 2026SPIE
    Current status of and future plans for PypeItT. E. Pickering, J. X. Prochaska, J. F. Hennawi, K. B. Westfall, D. Pelliccia, D. Reichwein, B. Holden, M. Brodheim et al. (13 authors)Cosmic dawn
    DOI
  6. 06Aug 2026SPIE
    Streamlining spectroscopic observations: a real-time data reduction display for Keck and beyondM. Brodheim, E. Jeschke, K. B. Westfall, D. Pelliccia, J. X. Prochaska, J. F. Hennawi, R. Cooke, B. Holden et al. (10 authors)Cosmic dawn
    DOI
  7. 07Jul 2026A&A
    Euclid: Discovery of 31 new quasars at 6.6 < z < 7.8D. Yang, J. F. Hennawi, F. Guarneri, J. Wolf, S. Belladitta, J. Schindler, A. C. N. Hughes, E. Bañados et al. (214 authors); UCSB: J. HuangCosmic dawn
    arXiv:2607.03432
  8. 08Jul 2026A&A
    Euclid: A UV-faint quasar in a highly luminous star-forming host galaxy at z ≍ 7.7S. Belladitta, R. Decarli, E. Bañados, F. Walter, D. Yang, F. Guarneri, K. Jahnke, S. Bisogni et al. (183 authors); UCSB: J. F. HennawiCosmic dawn
    arXiv:2607.03430
  9. 09Jul 2026ApJ
    ASPIRE: The Environments and Dark Matter Halos of Luminous Quasars in the Epoch of ReionizationF. Wang, J. B. Champagne, J. Huang, J. Yang, J. F. Hennawi, X. Fan, H. Zhang, T. Costa et al. (45 authors)Cosmic dawn
    arXiv:2602.04979
  10. 10Jun 2026arXiv
    A Measurement of the Thermal and Ionization State of the IGM at z < 0.5T. Hu, V. Khaire, J. F. Hennawi, T. M. Tripp, J. Onorbe, M. Walther, Z. LukicCosmic dawn
    arXiv:2606.05006

All papers by Joseph Hennawi

Everyone in the group