TY - JOUR
T1 - Photometric properties of reionization-epoch galaxies in the simba simulations
AU - Wu, Xiaohan
AU - Davé, Romeel
AU - Tacchella, Sandro
AU - Lotz, Jennifer
N1 - Funding Information:
The computing equipment to run SIMBA was funded by BEIS capital funding via STFC capital grants ST/P002293/1, ST/R002371/1, and ST/S002502/1, Durham University, and STFC operations grant ST/R000832/1.
Publisher Copyright:
© 2020 The Author(s).
PY - 2020/6/1
Y1 - 2020/6/1
N2 - 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.
AB - 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.
KW - galaxies: Evolution
KW - galaxies: Formation
KW - galaxies: High-redshift
KW - galaxies: Photometry
KW - galaxies: Stellar content
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U2 - 10.1093/mnras/staa1044
DO - 10.1093/mnras/staa1044
M3 - Article
AN - SCOPUS:85092001178
VL - 494
SP - 5636
EP - 5651
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -