{
  "id": "1911.06330",
  "version": "v1",
  "published": "2019-11-14T19:00:00.000Z",
  "updated": "2019-11-14T19:00:00.000Z",
  "title": "Photometric properties of reionization-epoch galaxies in the Simba simulations",
  "authors": [
    "Xiaohan Wu",
    "Romeel Davé",
    "Sandro Tacchella",
    "Jennifer Lotz"
  ],
  "comment": "13 pages, submitted to MNRAS, comments welcome",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "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 ($\\beta$) 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 $z\\sim 6$ than at $z\\sim 2$, suggesting that rapid early enrichment (and dust growth) is necessary to match the observed $\\beta$. We find that $\\beta$ is much 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 color gradients within galaxies. These predictions will be testable with JWST.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-11-14T19:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "reionization-epoch galaxies",
      "photometric properties",
      "james webb space telescope",
      "simba simulations",
      "mock james webb space"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}