Prospects for Detecting C II Emission during the Epoch of Reionization

We produce simulations of the atomic C ii line emission in large sky fields in order to determine the current and future prospects for mapping this line during the high-redshift epoch of reionization. We calculate the C ii line intensity, redshift evolution, and spatial fluctuations using observational relations between C ii emission and the galaxy star formation rate over the frequency range 200-300 GHz. We estimate an averaged intensity of {I}C\II=(4+/- 2)× {10}2 {Jy} {{sr}}-1 in the redshift range z ˜ 5.3-8.5. Observations of the C ii emission in this frequency range will suffer contamination from emission lines at lower redshifts, in particular CO rotational lines. Using simulations, we estimated the CO contamination to be {I}{CO}≈ {10}3 {Jy} {{sr}}-1 (originating from galaxies at z \lt 2.5). Using detailed simulations of the C ii and CO emission across a range of redshifts, we generate maps as a function of angle and frequency, fully taking into account this resolution and light-cone effects. In order to reduce the foreground contamination, we find that we should mask galaxies below redshifts ˜2.5 with a CO(J:2-1) to CO(J:6-5) line flux density higher than 5× {10}-22 W {m}-2 or an AB magnitude lower than {m}K=22. We estimate that the additional continuum contamination originating in emission from stars and in dust, free-free, free-bound, and two-photon emission in the interstellar medium is of the order of {10}5 {Jy} {{sr}}-1, which is well above the expected C ii signal. We also consider the possibility of cross-correlating foreground lines with galaxy surveys in order to probe the intensity of the foregrounds. Finally, we discuss the expected constraints from two experiments capable of measuring the expected C ii power spectrum