SGAME Simulations of the [CII], [OI], and [OIII] Line Emission from Star-forming Galaxies at z≲ 6

Karen Olsen, Thomas R. Greve, Desika Narayanan, Robert Thompson, Romeel Davé, Luis Niebla Rios, Stephanie Stawinski

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Of the almost 40 star-forming galaxies at z ≥ 5 (not counting quasi-stellar objects) observed in [CII] to date, nearly half are either very faint in [CII] or not detected at all, and fall well below expectations based on locally derived relations between star formation rate and [CII] luminosity. This has raised questions as to how reliable [CII] is as a tracer of star formation activity at these epochs and how factors such as metallicity might affect the [CII] emission. Combining cosmological zoom simulations of galaxies with SGAME (SImulator of GAlaxy Millimeter/ submillimeter Emission), we modeled the multiphased interstellar medium (ISM) and its emission in [CII] , as well as in [OI] and [OIII], from 30 main-sequence galaxies at z ≲6 with star formation rates ∼323 M· yr-1, stellar masses ∼ 0.7 8 109 M·, and metallicities ∼ 0.1 0.4 Z?. The simulations are able to reproduce the aforementioned [CII] faintness of some normal star-forming galaxy sources at z 5. In terms of [OI] and [OIII], very few observations are available at z 5, but our simulations match two of the three existing z 5 detections of [OIII] and are furthermore roughly consistent with the [OI] and [OIII] luminosity relations with star formation rate observed for local starburst galaxies. We find that the [CII] emission is dominated by the diffuse ionized gas phase and molecular clouds, which on average contribute ∼66% and ∼27%, respectively. The molecular gas, which constitutes only ∼10% of the total gas mass, is thus a more efficient emitter of [CII] than the ionized gas, which makes up ∼85% of the total gas mass. A principal component analysis shows that the [CII] luminosity correlates with the star formation activity of a galaxy as well as its average metallicity. The low metallicities of our simulations together with their low molecular gas mass fractions can account for their [CII] faintness, and we suggest that these factors may also be responsible for the [CII] -faint normal galaxies observed at these early epochs.

Original languageEnglish (US)
Article number105
JournalAstrophysical Journal
Volume846
Issue number2
DOIs
StatePublished - Sep 10 2017

Keywords

  • cosmology: theory
  • galaxies: ISM
  • galaxies: high-redshift
  • line: formation
  • methods: numerical
  • submillimeter: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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