{
  "id": "2212.02522",
  "version": "v1",
  "published": "2022-12-05T19:00:03.000Z",
  "updated": "2022-12-05T19:00:03.000Z",
  "title": "Emission-line properties of IllustrisTNG galaxies: from local diagnostic diagrams to high-redshift predictions for JWST",
  "authors": [
    "Michaela Hirschmann",
    "Stephane Charlot",
    "Anna Feltre",
    "Emma Curtis-Lake",
    "Rachel S. Somerville",
    "Jacopo Chevallard",
    "Ena Choi",
    "Dylan Nelson",
    "Christophe Morisset",
    "Adele Plat",
    "Alba Vidal-Garcia"
  ],
  "comment": "28 pages, 15 figures, submitted to MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We compute synthetic, rest-frame optical and ultraviolet (UV) emission-line properties of galaxy populations at redshifts from z$\\approx$0 to z=8 in a full cosmological framework. We achieve this by coupling, in post-processing, the cosmological IllustrisTNG simulations with new-generation nebular-emission models, accounting for line emission from young stars, post-asymptotic-giant-branch (PAGB) stars, accreting black holes (BHs) and, for the first time, fast radiative shocks. The optical emission-line properties of simulated galaxies dominated by different ionizing sources are largely consistent with those expected from classical diagnostic diagrams and reflect the observed increase in [OIII]/H$\\beta$ at fixed [NII]/H$\\alpha$ and the evolution of the H$\\alpha$, [OIII]$\\lambda5007$ and [OII]$\\lambda3727$ luminosity functions from z$\\approx$0 to z$\\sim$2. At higher redshift, we find that the emission-line galaxy population is dominated by star-forming and active galaxies, with negligible fractions of shock- and PAGB-dominated galaxies. We highlight 10 UV-diagnostic diagrams able to robustly identify the dominant ionizing sources in high-redshift galaxies. We also compute the evolution of several optical- and UV-line luminosity functions from z=4 to z=7, and the number of galaxies expected to be detectable per field of view in deep, medium-resolution spectroscopic observations with the NIRSpec instrument on board the James Webb Space Telescope. We find that 2-hour-long exposures are sufficient to achieve unbiased censuses of H$\\alpha$ and [OIII]$\\lambda5007$ emitters, while at least 5 hours are required for H$\\beta$, and even 10 hours will detect only progressively smaller fractions of [OII]$\\lambda3727$, OIII]$\\lambda1663$, CIII]$\\lambda1908$, CIV$\\lambda1550$, [NII]$\\lambda6584$, SiIII]$\\lambda1888$ and HeII$\\lambda1640$ emitters, especially in the presence of dust.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-12-05T19:00:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "emission-line properties",
      "local diagnostic diagrams",
      "high-redshift predictions",
      "illustristng galaxies",
      "james webb space telescope"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 28,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}