Nebular line emission fromz> 7 galaxies in a cosmological simulation: rest-frame UV to optical lines

Abstract

We have performed very large and high resolution cosmological hydrodynamic simulations in order to investigate detectability of nebular lines in the rest-frame ultraviolet (UV) to optical wavelength range from galaxies at $z > 7$. We find that the expected line fluxes are very well correlated with apparent UV magnitudes. The C IV $1549 \rm \AA$ and the C III] $1909 \rm \AA$ lines of galaxies brighter than $26~ \rm AB$ are detectable with current facilities such as the VLT/XShooter and the Keck/MOSFIRE. Metal lines such as C IV $1549 \rm \AA$, C III] $1909 \rm \AA$, [O II] $3727 \rm \AA$ and [O III] $4959/5007 \rm \AA$ can be good targets for the spectroscopic observation with Thirty Meter Telescope (TMT), European Extremely Large Telescope (E-ELT), Giant Magellan Telescope (GMT) and James Webb Space Telescope (JWST). H$\alpha$ and H$\beta$ lines are also expected to be detectable with these telescopes. We also predict detectability of the nebular lines for $z > 10$ galaxies that will be found with JWST, Wide-Field Infrared Survey Telescope (WFIRST) and First Light And Reionization Explorer (FLARE) $(11 \leq z \leq 15$). We conclude that the C IV $1549 \rm \AA$, C III] $1909 \rm \AA$, [O III] $4959/5007 \rm \AA$ and H$\beta$ lines even from $z \sim 15$ galaxies can be strong targets for TMT, ELT and JWST. We also find that the magnification by gravitational lensing is of great help to detect such high-$z$ galaxies. According to our model, the C III] $1909 \rm \AA$ line in $z > 9$ galaxy candidates is detectable even using the current facilities.