Photometric properties of reionization-epoch galaxies in the simba simulations

Xiaohan Wu, Romeel Davé, Sandro Tacchella, Jennifer Lotz

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


We study the photometric properties and sizes of the reionization-epoch galaxies in high-resolution simba cosmological hydrodynamical simulations with box sizes of [25,50]\, h-1 Mpc}. Assuming various attenuation laws, we compute photometry by extincting each star particle's spectrum using the line-of-sight gas metal column density. The predicted ultraviolet luminosity function (UVLF) generally agrees with observations at z = 6, owing to a partial cancellation between the high metallicities of the simulated galaxies and lower dust-to-metal ratios. The simulated z = 8 UVLF is low compared to observations, likely owing to excessive dust extinction. simba predicts UV continuum slopes (β) in agreement with the z = 6 observations, with the best agreement obtained using a Calzetti extinction law. Interestingly, the gas-phase mass-metallicity relation in simba is higher at z ∼6 than at z ∼2, suggesting that rapid early enrichment (and dust growth) might be necessary to match the observed β. We find that β is more sensitive to the dust extinction law than the UVLF. By generating mock James Webb Space Telescope (JWST) images and analysing in a manner similar to observations, we show that simba's galaxy size-luminosity relation well reproduces the current z = 6 Hubble observations. Unlike observations at lower redshifts, simba predicts similar rest-UV and rest-optical sizes of z = 6 galaxies, owing to weak age gradients and dust extinction in star-forming regions counteract each other to weaken the colour gradients within galaxies. These predictions will be testable with JWST.

Original languageEnglish (US)
Pages (from-to)5636-5651
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jun 1 2020


  • galaxies: Evolution
  • galaxies: Formation
  • galaxies: High-redshift
  • galaxies: Photometry
  • galaxies: Stellar content

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Photometric properties of reionization-epoch galaxies in the simba simulations'. Together they form a unique fingerprint.

Cite this