We discuss the detectability of high-redshift galaxies via [ C ii ] 158 \mu m line emission by coupling an analytic model with cosmological Smoothed Particle Hydrodynamics ( SPH ) simulations that are based on the concordance \Lambda cold dark matter ( CDM ) model .
Our analytic model describes a multiphase interstellar medium ( ISM ) irradiated by the far ultra-violet ( FUV ) radiation from local star-forming regions , and it calculates thermal and ionization equilibrium between cooling and heating .
The model allows us to predict the mass fraction of a cold neutral medium ( CNM ) embedded in a warm neutral medium ( WNM ) .
Our cosmological SPH simulations include a treatment of radiative cooling/heating , star formation , and feedback effects from supernovae and galactic winds .
Using our method , we make predictions for the [ C ii ] luminosity from high-redshift galaxies which can be directly compared with upcoming observations by the Atacama Large Millimeter Array ( ALMA ) and the Space Infrared Telescope for Cosmology and Astrophysics ( SPICA ) .
We find that the number density of high-redshift galaxies detectable by ALMA and SPICA via [ C ii ] emission depends significantly on the amount of neutral gas which is highly uncertain .
Our calculations suggest that , in a CDM universe , most [ C ii ] sources at z = 3 are faint objects with S _ { \nu } < 0.01 mJy .
Lyman-break galaxies ( LBGs ) brighter than R _ { AB } = 23.5 mag are expected to have flux densities S _ { \nu } = 1 - 3 mJy depending on the strength of galactic wind feedback .
The recommended observing strategy for ALMA and SPICA is to aim at very bright LBGs or star-forming DRG/BzK galaxies .