Intensity mapping provides a unique means to probe the epoch of reionization
(EoR), when the neutral intergalactic medium was ionized by the energetic
photons emitted from the first galaxies. The [CII] 158μm fine-structure
line is typically one of the brightest emission lines of star-forming galaxies
and thus a promising tracer of the global EoR star-formation activity. However,
[CII] intensity maps at 6≲z≲8 are contaminated by
interloping CO rotational line emission (3≤Jupp≤6) from
lower-redshift galaxies. Here we present a strategy to remove the foreground
contamination in upcoming [CII] intensity mapping experiments, guided by a
model of CO emission from foreground galaxies. The model is based on empirical
measurements of the mean and scatter of the total infrared luminosities of
galaxies at z108M⊙
selected in K-band from the COSMOS/UltraVISTA survey, which can be converted
to CO line strengths. For a mock field of the Tomographic Ionized-carbon
Mapping Experiment (TIME), we find that masking out the "voxels"
(spectral-spatial elements) containing foreground galaxies identified using an
optimized CO flux threshold results in a z-dependent criterion mKAB≲22 (or M∗≳109M⊙) at z<1 and makes a [CII]/COtot power ratio of ≳10 at k=0.1h/Mpc achievable, at the cost of a moderate ≲8% loss of total
survey volume.Comment: 14 figures, 4 tables, re-submitted to ApJ after addressing reviewer's
comments. Comments welcom