Detectability of [Cii] 158 μm Emission from High‐Redshift Galaxies: Predictions for ALMA andSPICA

We discuss the detectability of high-redshift galaxies via [CII] 158 micronline emission by coupling an analytic model with cosmological Smoothed ParticleHydrodynamics (SPH) simulations that are based on the concordance Lambda colddark matter (CDM) model. Our analytic model describes a multiphase interstellarmedium irradiated by the far ultra-violet radiation from local star-formingregions, and it calculates thermal and ionization equilibrium between coolingand heating. The model allows us to predict the mass fraction of a cold neutralmedium (CNM) embedded in a warm neutral medium (WNM). Our cosmological SPHsimulations include a treatment of radiative cooling/heating, star formation,and feedback effects from supernovae and galactic winds. Using our method, wemake predictions for the [CII] luminosity from high-redshift galaxies which canbe directly compared with upcoming observations by the Atacama Large MillimeterArray (ALMA) and the Space Infrared Telescope for Cosmology and Astrophysics(SPICA). We find that the number density of high-redshift galaxies detectableby ALMA and SPICA via [CII] emission depends significantly on the amount ofneutral gas which is highly uncertain. Our calculations suggest that, in a CDMuniverse, most [CII] sources at z=3 are faint objects with \Snu < 0.01 mJy.Lyman-break galaxies (LBGs) brighter than R_AB=23.5 mag are expected to haveflux densities \Snu = 1-3 mJy depending on the strength of galactic windfeedback. The recommended observing strategy for ALMA and SPICA is to aim atvery bright LBGs or star-forming DRG/BzK galaxies.Comment: 39 pages, 13 figures, accepted to ApJ. Matched to the accepted versio